Sunday, December 23, 2007

Who Needs A Thermostat, Take Two

So I guess I'm not the only one thinking about using mobile WiFi enabled devices for controlling home automation devices.

Tuesday, December 18, 2007

One Size Fits All, or Reflections on EPA guidelines

So here cometh a fresh pair of thermostats (Honeywell RTH7500 and RiteTemp GPMG8085C), both equipped with default schedules taken from EnergyStar ® Program Requirements for Programmable Thermostats: Partner Commitments (look for Table 2: Acceptable Setpoint Times and Temperature Settings). It was summer, and the default settings were too cold for us, so we changed them.

But the defaults for the heating season were left in place.

Now that the heating season is here, and it is eventually getting quite cold outside, several interesting things are popping up.

First of all, let's take a look at default EPA compliant settings.

Wake: 6AM, 70°F.
Day: 8AM, 62°F.
Evening: 6PM, 70°F.
Sleep: 10PM, 62°F.

Then, let's go back and read the long rant about whether you should shut off your A/C or leave it running.

Then, let's take a look at the temperature spread for the schedule above. 8°F.

That's quite a lot.

The very reason I've started thinking about writing this article is that one of my units (Lennox split), being perfectly capable in cooling mode, seems to either hit the balance point, or otherwise severely degrade its performance, when the ambient temperature drops lower than about 45°F - and, as a result, it is unable to bring the zone it serves from 62°F to 70°F in two hours.

Even worse the temperature actually drops to about 65°F by 6AM, and it barely makes it to 68°F by 8AM - forget 62 to 70.

While this is definitely quite uncool, it also points out another fact that is not on the surface: the unit works at the top of its efficiency curve. It doesn't cycle, it spends initial 10-20 minutes approaching the design efficiency and stays there.

That was the positive, now, another negative - since it serves two rooms, one of which is about five times size the other - guess what, by the end of the two hour run the smaller room is HOT. Balancing the dampers manually will not help since it'll shoot the balance for other conditions - like, the evening, when the ambient temperature is significantly higher and the runtime of the unit is very short in comparison.

So, what's the point?

  • One should carefully examine defaults;
  • You can't get away without actually zoning the house - unless you want to shuffle everything all the day or suffer;
  • It would *really* pay back to come up with an idea to figure out to anticipate the *actual* performance of the unit for varying circumstances and make the system issue recommendations to you about what you should do in any particular case;
  • Which would imply the knowledge base and rule engines to analyze input and figure out dependencies (homework: see Google's statements how having access to massive amounts of data helps to figure out the trends and make correct decisions);
  • It would help to share data between installations (see how Valve managed to make Half Life 2 the most playable game for the same hardware utilizing statistics) and applying some brains;
Damn! DZ is going enterprise.

Hmm... Turned out not quite the way I started it - but oh well, I'll just leave it at that.

Saturday, December 8, 2007

Green Dryer

Looking outside of my window and seeing a giant plume of steam coming out of my dryer's exhaust.

Immediately thinking that next time I'll be doing remodeling around the laundry room, or building my own house, I'll definitely install an ERV capturing all that heat that is being wasted by the dryer in the heating season, and a bypass allowing it to escape in the cooling season.

Also thinking that it would be a dumbest idea possible to direct the dryer exhaust into the house because of associated humidity and smell.

Books: too obvious to think about

Usually, the Internet is the best source of information - at least, quickest accessible.

But it has a drawback - you won't find the information you're not specifically looking for. Maybe only as a collateral, but even in this case you have to know that it is relevant to the problem you're resolving - and this may not necessarily be obvious.

A while ago, I was trying to figure out whether it is safe to drill a 1 1/2" hole in a load bearing support beam. The consequences of a wrong decision would be catastrophic - the second floor will come crashing down, and no insurance would help. So I started looking for the solution, but, surprisingly, different sources were giving different advices.

It so happened that I visited a bookstore at the same time. By accident, I was passing by the section with all sorts of DIY books in it. Just out of curiosity, I decided to take a look.

Well, now I'm writing this article. Thanks to many of those books, now I know how to do wiring, framing, drywalling, texturing and painting, investigating installing windows and doors, flooring, all kinds of woodworking, will take a look at tiling when the time comes.

It's not that they are the source of ultimate wisdom. It's that there are things in every business that you simply have to know in order to do things - and those books give you the necessary headstart so you can looks ahead standing on the shoulders of giants. Or at least those who passed this road before you.

Another advice - don't rush buying those books - you'll spend a fortune. Each book is anywhere from $20 to $80. Make friends with your local library instead.

Wednesday, November 28, 2007

What kind of actuators are you using?

I'm now working on a maintenance ("Undead") release for Servomaster, which was originally created to provide the driver layer for register or damper actuators (as shown here).

A lot has changed since last modification was made to Servomaster - the code turned out to be rock stable and low maintenance. I could accept that as a sign of the fact that the code is perfect - but I'd rather go the other way and ask if it is so off the mark that you guys are speechless and simply walked away from it because you can't use it.

It would be really nice if you looked at the poll (scheduled to close on December 5 2007) and gave me a hint on what to concentrate on.

Tuesday, November 27, 2007

So what is a heat load calculation?

The answer is here (part of the homeowner's FAQ).

Jukebox 5.0p0 is out

After 2 years of countless changes, I've finally found time to package and release the "Undead" release of Jukebox - a precondition to "Undead" release of DZ (along with pending "Undead" release of Servomaster).

A platform independent RPM, source RPM and source tarball are available at SourceForge download location.

Monday, November 26, 2007

Code repository has been migrated to Subversion

SVN repository (including all historical commits, tags and branches) is now active.
CVS repository will no longer be used - but still available for archival purposes.

Monday, November 12, 2007

Who Needs A Thermostat?

I've been pondering about this question for a long, long time - starting in about 2001 when the only way to control DZ available was a debug panel, and last time in an essay about SWMBO Compliance Certification (Squeezebox is still a good candidate), but it seems that there's been a new development that might if not put an end to the fruitless search, then significantly widen the options available.

I'm talking about Android.

It remains to be seen how viable the platform is and how many hardware manufactures will jump on the bandwagon. But for now - having worked on different Google APIs (Checkout and Calendar in particular) I can say that it's sure going to be a hell of a fun ride, and I'm about to get busy installing the Android SDK and tinkering with it to see how well can a user interface for a HVAC system work on a cell phone.

Now, who needs a thermostat on the wall, really?

Tuesday, November 6, 2007

SketchUp + HVAC-CALC, part 3

(part 1)
(part 2)

Now, Official Google SketchUp blog reports that the beta version is available for download.

Hurry before they change their mind.

So what is a rack?

The answer is: it is a short name for a 19-inch rack.

An extremely useful thing for a computer geek with lots of equipment spread around the house.

Also, an extremely useful thing for any modern house - people don't usually think about how much equipment that needs connecting they already have, and what will change in the nearest future. Just think: VoIP, IPTV, Squeezebox, NAS (one meaning), NAS (another meaning).

In other words, if you've read all the articles above, know what the rack is and still think you won't need it in a couple of years... I don't even know what to say :)

Now, *can you* have it in your house is a completely different story for a different time. I'm currently midway into a pretty heavy remodeling involving 24U rack installation - hope to finish it in a few weeks and publish the report.

Tuesday, October 30, 2007

Rigid plastic conduit: unidirectional

Good judgment comes out of experience. Experience comes out of bad judgment.

It seems pretty obvious in hindsight, but somehow didn't come to my head that I might have problems running fish tape through a rigid plastic conduit with a few bends. Guess it is not usually a problem, otherwise it would be widely documented - or it may have been just my dumb luck, but...

Turned out that a wide and big 1" conduit run of 26ft with two 90° bends is not passable in either direction.

Took me a split second to realize why - the bell. The one that is at one end of each conduit component. The rest should be obvious.

Two conclusions:

  • Do a dry run - works pretty well with plastic conduit, it holds up pretty well and you can probably get away with running it through even though it's not glued together yet;
  • Plan ahead and remember that you may not be able to pass a conduit in one direction.
What did I end up with? Well... Had to cut the elbow out and reverse the direction. Don't be like me.

Saturday, October 20, 2007

Fake Air Returns: Watch Out

I remember reading a post at HVAC-Talk a few years ago when someone wrote that a contractor just cut a hole in drywall, installed a return air grill and claimed that it is exactly what it is supposed to be - a return. Long and heated discussion followed (HVAC-Talk expires threads, so the source is no longer available), with polar opinions being a) yes, it's acceptable and b) not at all, you must provide the path.

I've seen grills leading to dead spaces a few times afterwards, which makes me think this is not an exception.

Now that I'm learning framing - well, turns out that the building code explicitly calls for installing what is called fire blocking: two-by stud material that runs horizontally from stud to stud - every 10 ft measured vertically in stud bays. Fire blocking interrupts the upward flow of flames and heat.

Two lessons:

  1. There is no easy way to install an air return in a room;
  2. There is no easy way to wire anything - studs (at the minimum) are horizontal obstacles, fire blocking (at the minimum) are vertical obstacles.

Thursday, October 18, 2007

SketchUp + HVAC-CALC, part 2

You've read it here first. Now someone closer to the subject area implemented it: Energy Analysis Tool for SketchUp.

Told you.

Random Notes: Timing and Blueprints

Random note #1: One thing I have not regretted, in a hindsight, that I've started the wiring project right now - in local mid-season. When the insulation is disturbed, it doesn't function properly anymore, and had this happened in the middle of the summer (or in the middle of the winter for those farther North), it would've been bad.

Random note #2: SketchUp is the best thing since sliced bread for DIY projects. More and more professionals are starting to realize the importance of it (see the article on timber framing, for example). It works for project at almost any scale - the house model I've built, for example, has everything from the yard on the top of the scale to individual screws in places where I've laid conduit, on the bottom of it. Start with 3d Warehouse (Thai House Blueprints is a beautiful example), don't forget the SketchUp Blog.

Tuesday, October 16, 2007

The Great Wiring Project, part 4

The Great Wiring Project, part 1
The Great Wiring Project, part 2
The Great Wiring Project, part 3

This one is going to be really short: I thought I'd be able to get away without a patch panel. No such luck. Off looking for one. Suggestions welcome.

(to be continued)

Monday, October 15, 2007

The Great Wiring Project, part 3

The Great Wiring Project, part 1
The Great Wiring Project, part 2

There is this usual dilemma - whether to run just the wires, or run the conduit. Given the fact that a) the opportunity presented itself and b) I know I would be able to utilize all the paths the conduit offers and not simply show it off to my friends, the decision was made to run the conduit.

Oh boy.

Remember, at the very beginning I said forget elegant? My particular problem (which is the more likely to happen to you the more owners it had) was caused by the fact the house's been remodeled. As a result, observations on one part of the structure were absolutely not applicable to another. To add insult to injury, the addition was partly a hack job (imagine my surprise when I uncovered a 4x4 beam in the middle of a wall... On top on two 2x4s... Turned out, there was a door before...)

There was a phrase in a book on wiring I read, "Be prepared to drill a few exploratory holes". Actually, that was a euphemism. They probably meant "Be prepared to tear the walls down".

Would the process be easier if I decided to run wires? Not really. It would only be easier if I was familiar with the building blueprints and was doing work on the same floor plan for the umpteenth time. For a case of a single DIY work, no, it wouldn't have been.

One reason why it wouldn't have been possible to even piggyback and/or replace existing wiring while running wires (as opposed to conduit) is that existing wiring is stapled down to studs very tightly and it either doesn't move at all, or any part that is thicker than the actual cable you're trying to piggyback will invariably get stuck at the first staple you meet.

Another one is that insulation offers a formidable obstacle. It is not really possible to guess where the fish tape is going (and those words about "non-curling" fish tape are a joke, too).

A word about fish tapes and cables - give it a LOT of padding. A run from the left side of a 14 ft wide room to the right side, up and over the ceiling, took whopping 35 feet of conduit - so had I bought a 25ft fish tape, I'd be kicking myself in the butt right now. Fortunately, I've bought a 50ft one - but now I'm not even sure *that* would be sufficient (the project is far from over). Crossing my fingers for now.

Back to conduits...

Rigid plastic conduit is a joy to work with (I've used 1/2" for single cable runs, 3/4" for double cable runs and 1" for the trunk). Flexible plastic conduit (there are several color coded varieties, out of which I've seen high voltage blue and low voltage orange) is surprisingly rigid at times - and don't let it spring in your hands and knock you on the forehead (ask me how I know). Did I mention wear goggles at all times?

Snap-on connectors for the flexible plastic conduit are, in fact, one-time use - it's a pain to disconnect one once you snapped it on. I've used threaded ones to connect conduit to the boxes, just to save myself some aggravation in case if I ever have to disconnect one.

Boxes. There's not much difference between cutting a smaller hole and using an existing work box, or cutting a bigger hole and using a new work box. If you want to route the conduit to existing wall plate, second option is unavoidable - unless the box can be taken out. I decided to use new work boxes everywhere (except one really simple run) - there's lots of holes to patch already anyway, a few extra doesn't make much difference, but makes the general quality of installation much more enjoyable.

The Great Wiring Project, part 1
The Great Wiring Project, part 2
(to be continued)

Sunday, October 14, 2007

The Great Wiring Project, part 2

The Great Wiring Project, part 1
The Great Wiring Project, part 3

I just realized that this story becomes chaotic pretty fast. Hmm... Let it be - and when it's all said and done, I'll reorganize it so it makes chronological sense for those planning, and find it a permanent place at DZ site.


If you think you have all the tools, think again. The only tool I had to buy was a high torque drill - your usual 1/3 HP kind gets stuck when equipped with bits starting about 7/8", and, in general, more powerful tools mean less kickback and more precision.

Drill bits differ - spades are cheaper but very rough, splinter wood badly on exit, but sometimes may be the only option. Forstner bits are much more expensive, but produce an exact opening - and unlike spades which go astray under slightest provocation, they are self-guiding and it is possible to use one to enlarge a preexisting hole. Remember that Forstner bits are usually pretty short - and the lengths you will have to drill through may exceed 8" (visualize door header left in the wall when someone decided they no longer wanted a door there).

Instead of buying a long bit, buy a short one and an extender - otherwise you might end up a short bit *and* a long bit, which is not that cost effective keeping in mind that one extender will work with many bits.

I will try to avoid using center bits for a while - the Ridgid one I bought broke on the first try - the center piece disengaged from the rest of the bit and got stuck in the wood. Took me lengthy and painful efforts to get it out of there - it happened in quite an inaccessible place.

Absolute must for this project (in my book) is a jigsaw - though you may get away with a drywall knife. It'll just take longer. Decent fish tape won't hurt, either.

A really bad surprise was the amount of dust drywall generates. The cleanest solution is to have a helper with a shopvac standing next to you - worked pretty well for me. Nevertheless, invest in a decent respirator (expensive) and goggles (cheapest and biggest work just fine). Cover all things with vents on the upside with a dust-opaque cloth (plastic is not a good idea because it will not let the air from those vents up - you're risking to kill your equipment).

Don't forget to replace the HVAC filters when you're done.

Be prepared that you will damage or destroy insulation behind the walls you're opening, so plan on either taking extreme measures not to contaminate it with drywall dust (I don't think it's possible), or live with it, or reinforce or replace the insulation altogether (may or may not be possible, depending on the location and size of the opening). Also remember that fiberglass does get under your skin - you may not notice it within first five minutes, but you will for sure notice it within first five days.

The Great Wiring Project, part 1
The Great Wiring Project, part 3

The Great Wiring Project, part 1

The Great Wiring Project, part 2
The Great Wiring Project, part 3

Initially, it was just about tidying up power cables, interconnections and speaker wires for the home theater. For about 30 seconds. Then I realized that the cable path is right next to air supply vents, and the rest was pretty simple. In theory.

It is often said that wiring is difficult. Not really - but it is sure different from most of the jobs people do for living, so you have to acquire some experience before it becomes easy. "How to do wiring" is a topic beaten to death elsewhere, so I'll try to concentrate on things I have not seen mentioned during all those years I've been planning to do the wiring.

Now it is a good time to recall the saying "Good judgment comes from experience. Experience comes from bad judgment". Not that I've had a lot of bad judgment calls, but some of them were pretty close - and I hope you folks do learn on my mistakes .

The first observation is - forget all hopes to make it all elegant. You can only make things elegant with some planning and forethought, and when you start your own wiring (or any kind of remodeling that makes framing and existing wires exposed in any way) - you will promptly realize that forethought and planning is not something present in buildings mass produced to satisfy skyrocketing minute-driven demand for new housing when the interest rate plummets.

Second observation is - forget the code. You will not see the code followed anywhere where the building inspector could not peek into when the building is finished. Not that you won't be brought to responsibility when something bad happens to the stuff you built, so be thoroughly prepared to present evidence that you did it all by code - there are two standards, for "them" and for "you".

The Great Wiring Project, part 2
The Great Wiring Project, part 3

Saturday, October 13, 2007

I'm waking up, too

Those who have been following this project since days long gone may have noticed that nothing really significant appeared here in about last two years or so.

There were many reasons for it - I've changed the house (couldn't staple those nice looking blue cables to white walls any longer), changed the job (free time have become scarce), and all the things that could've been done to the project itself were essentially done - there was no significant itch to scratch anymore.

All of this changed again recently - energy prices are going up, kids are growing up, conditions change, and my last electric bill was whopping $420. Twice of what it was two years ago.

So the itch is there again.

And the last straw, I've made a mistake of undertaking a wiring project - and of course, as soon as I've opened the walls, I've realized that this is a perfect opportunity to install DZ again - and as soon as it is installed, two years worth of unimplemented ideas will start begging to be implemented and perfected.

So, the short term plan goes like this: Finish wiring, install sensors, install dampers, install DZ and roll on. Will not be fast (a simple speaker wiring project turned out into an exercise in advanced framing, insulation, conduit installation, drywalling, texturing and painting; plus, a new server room will be built to accommodate everything) - but it will be thorough.

Stay tuned.

Big guys are waking up

At last (seven years later), there are signs of companies that manufacture and install zoning systems and components for living waking up and paying attention to their Internet literate customers. First time ever, links from them (as opposed to mere installers) appear on the first page of Google search for related terms.


It appears, though, that they have to pay for listings to have them above DIY Zoning - which was the purpose of the project to begin with.

Let's see what the future holds.

Monday, October 8, 2007

Look, Ma, The Zone Control Blog!

Not this one. The one Jackson Systems created, here. Fresh one, too - started on September 24 2007.

Don't know about you, but I'm definitely looking forward to reading it. I sincerely hope it's not going to be an another clog.

Clog, n - a type of website where entries are made (such as in a journal or diary), displayed in a reverse chronological order. Clogs differ from Blogs because the content is typically aligned with a marketing or press release strategy in order to promote the company or corporation. -- Wikipedia entry on Clog

Thursday, October 4, 2007

The joys of DIY

I seem to be having extremely bad luck with contractors. It can easily be that I'm in a severe violation of the "secret of life is: have low expectations" principle. Most probable explanation, though, is that they just want to get their work day over with and go home. I guess they hope nobody would notice.

So my car breaks down (they do that). I get it to the dealership, they fix it... and put a dent in the door. I politely point out that the door needs to be fixed, they politely agree, fix the dent... and break the center console. And blame it on the car wash guys (never mind that I have specifically asked not to wash the car - last time they did, it cost them (not me - it was still under warranty) $1572 and spare change to fix the headlights the "car wash guys" killed).

It is plausible to assume that whoever dented the door hoped nobody would notice. It is also plausible to assume that whoever broke the console hoped nobody would notice. They just didn't expect that to happen twice to the same person in a row.

Fine... When in two weeks my window regulator breaks down and the window gets stuck halfway down, I take my sweet time to fix it, and my sweet money to buy the tools necessary (never before in my life I had a need for a torx bit set and a torque wrench - have them now). Spent a week, but next time it'll be an hour - procedures learned, tools acquired.

Oh, and I've also fixed all the things that the guys at the dealership broke the first time the window regulator broke, a couple of years ago. Half of pistons holding the door panel were broken. The door was rattling all this time, I've never had time to address the problem in depth, told dealership, they said "they all do that with age". Right. Few pistons fifty cents each - I bet they have buckets of those at each corner of the shop in abundance. But no, they didn't care to replace the ones they broke. A guy I met today explained to me: auto mechanics get paid by the job, not by the hour. They'd rather get paid for two jobs - and then two again, next time when the complaint is handled.

So, I've eventually gotten myself to route the wires through the walls. So I cut the walls open, and what do I see? Correct, 120V NM cable bundled together with telephone cable and stapled to the studs with metal staples. Forget the building codes, who is going to rip the drywall open to check it? Next thing I see is a 120V NM cable suspended across 20ft gap... with plastic conduit tube simply hanging on it. Not connected to anything. Next thing I see is a web of telephone wires, just knotted together and suspended in the middle of the attic.

I'm not even talking about a 1 ft diameter flex tubing branch crammed in snaking between framing members so its length is almost twice the distance it has to cover, and eventually feeding a 6x6 inch register.

I guess they hoped nobody would notice.

So what recourse do I have? None, really. Except you do have to take your time and energy to study all the sources on the subject matter and know what you're talking about when you're talking to contractors (but then they get pissed at you and might eventually tell you "you're too #%So what recurse do I have? None, really. Except you do have to take your time and energy to study all the sources on the subject matter and know what you're talking about when you're talking to contractors (but then they get pissed at you and might eventually tell you "you're too #%$&ng smart, I'm not gonna do business with you"), or simply learn to do it yourself.
amp;ng smart, I'm not gonna do business with you"), or simply learn to do it yourself.

Yes, the price I've paid for the tools to fix that car window would've paid for the labor. ONCE. Yes, I've already invested over three hundred dollars in tools necessary to do wiring (quality fish tape, drill bits, drill with enough torque to handle inch and a quarter holes, cables, connectors, wall plates, and so on and so forth), but I'm perfectly sure that at the end of the day, I'll be proud of the work I've done, and will have learned something to top it up.

Not all DIY is about saving a buck. Sometimes, it's about the long standing quality and the satisfaction of a job well done.

Sunday, August 12, 2007

OUCH! This Is Not Design

This is a kind of engineering I'm trying to avoid: Window A/C Keeps Car Cool.

Feel free to peruse the Digg article for trivial criticism.

Meanwhile, instead of joining the crowd in bashing the guy (totally deserved, I must say) I'll try to be constructive and talk a little about why I claim DZ is not a hack like that.

First of all, two projects (let's call the other one The Window Hack, TWH for short, from now on) solve different tasks, though on surface they may seem to solve the same - inadequate cooling.

TWH is supposed to solve the problem of a HVAC unit, perfectly good by design, but poor by execution, that keeps breaking and sucking money. In other words, it addresses the problem of financial delinquency. With many side effects, not the least of which are the aggravation of outbound cash flow (air drag => $$$ for extra gas) and consumer safety (imagine where that box flies in case of a collision, or if it is simply torn off by the air stream at 70mph).

DZ, on the other hand, is aimed at solving a problem of inadequate HVAC design. Moreover, it solves it in a scalable way that allows to start getting immediate improvements with very little investment, and keep investing into hardware and getting tangible benefits all the way up to the sky.

First of all, you can just install the sensor network and stop right there. Analysis of what you will see may just as well allow you to make adjustments to your home infrastructure in order to bring it to your home comfort requirements.

Then, you can run DZ in passive mode and never touch the HVAC - gives the skittish ones their piece of mind and improvements in home comfort.

Or, you can just go all the way and reap the benefits.

In any case, amount of improvements you get is proportional to your invesment - would it be your time or your money.

Breaking it down to components -

You can start with adding a $10 R/C servo and little labor to get a simplistic motorized register. Like I was saying before, this solution was good enough to work for two years without any necessity to improve it.

Or, you can go for an industrial grade modulating damper - the first Google hit for such a thing that has a price listed puts it at $180.01. I suspect that the actual price will be significantly higher - usually, you have to log in to see the price, and I'm afraid that not everybody would be able to even get an account, it may be restricted to certain audience. Consequently, even that price, whatever it is, is subject to markups all the way up before you are told the final figure.

But if you want to use an industrial grade damper with DZ and can afford it - be my guest, it is not only possible, but accounted for in the system architecture. Oh, and you can have a mixed set of dampers at the same time, so you don't have to spend all that money at the same time.

Same is true for the HVAC unit - DZ can work with a crappy 30 year old HVAC (and, in fact, it did for two years) and allow you to extract significant home comfort improvements even out of that monster. But if you cough up some cash and install a state of art, multistage, variable speed unit (that'll cost you somewhere north of $10,000) - it will happily recognize the features available and will allow you to squeeze even more use out of that.

Bottom line: you get what you paid for. But, you can spend a cent at a time here and there and keep getting returns on what you spend with even minor investments - you don't need to get a loan in the bank to make that happen.

Monday, August 6, 2007

Doctor, it hurts when I walk this way, or HVAC Checklist

Free Idiot Test - $5
Patient: Doctor, it hurts when I walk this way...
Doctor: Don't walk this way, then...

Buying a house is a major pain.

What I was talking about, again? Ah, the usual complaints people have about the house they just bought.

  • A particular register is too noisy.
  • Return air grill is too noisy.
  • Air handler is too noisy.
  • Condenser is too noisy.
  • A particular room is too cold or too hot.
  • One floor is hotter than the other.
  • A room feels stuffy when the doors are closed.
  • A/C can't keep up with the heat.
  • Heater can't keep up with the cold.
  • Air in the house feels musty.
  • There are dust traces outside of registers.
  • Bathroom walls stay moist forever.
The list becomes pretty long pretty fast, but it can grow significantly longer.

For one single reason: people don't pay attention to HVAC. They think about anything and everything except HVAC. And realize they're in trouble just as the train has just departed.

So, how this can be fixed? And who is in a position to fix it? Unsurprisingly, people who can benefit from this, at the same time helping potential victims avoid being trapped - realtors and, to less extent, HVAC servicemen.

It's a double edged sword, though - for realtors, HVAC is just one more hoop to jump through. For both the buyer's and seller's agents, this is an obstacle on the road between today and the moment they cash the commission check. It would take a person of high integrity to step away from otherwise inevitable financial gain - but wait, we're getting into old good argument about reputation...

Theoretically, it should be a part of home inspection report, but I'm yet to see one that would address those particular issues, or even if it did - somehow a $20 register doesn't seem to register, no pun intended, when a typical house could very well cost north of half a million dollars and this is exactly how much is at stake when you are considering buying it (or so you think at the moment. Actually, the stakes are even higher - your well being is at stake). Especially keeping in mind the fact that issues like this will surface well into the process, after you have already decided to make an offer, paid inspection fees and generally are tied up pretty fast.

Another issue is that a person or a crew that will perform the inspection is not necessarily highly proficient in HVAC. Yes, they know the motions (check the supply air temperature, etc.) - but what they do may not be enough. Then again, it is applicable to every possible subsystem in the house (Gawd! Don't ask me about the state the wiring system was in at the house I live in...) So the advice here would be to actually make an extra step and pay a HVAC contractor (yes, and the plumber, and the electrician, and the roofer - the list goes on and on). I don't think you would regret this much, especially in today's market - you may be ecstatic and think you've just coaxed the poor desperate seller and made a steal, but tomorrow will come and you will see that you're already upside down with all the problems you've overlooked.

But let's take a step back and read the complaints above. All of them share one property: they are obvious. All you need to do is pay attention.

There are certain things you can do in order to make those those problems more obvious.
  • The most difficult - look for a new house during most unfavorable season. I know, it is difficult, and plans may not work this way, and it would be difficult to have extreme conditions for the heater in the middle of the summer, but at least try. According to 6 years of observations, for Arizona (actually, North Valley, but it may be good enough for all of South Arizona) the coldest period appears to be a second half of January, extending into first half of February. Hottest period is usually the second half of July - immediately followed by the humid period (one thing I can say, though, is that if you have humidity problems in Arizona, out of all places, you'd better start walking away from that house before you finish reading this article).
  • Next best approximation is to schedule a visit during most unfavorable time of day. Hottest time of day, as far as cooling is concerned is around 5PM. Don't even hope to get the coldest time of day - unless you get to spend the night at the house, which, in this favorable to buyer market, may not be impossible.
  • Spend as much time at the house as you possibly can.
  • Make sure the doors stay closed during this time.
  • Open the curtains, don't take no for an answer.
  • Shut off the fans. Even if you like them and want them. Fans may mask the problem that already exists.
  • See where the thermostat setpoint is. Don't be cheap and spend $20-30 at RadioShack to buy a decent digital thermometer, say, 63-1087 or 63-1088 (disclaimer: I haven't tried those. The one I have is 63-1032, but it is wired).
  • Listen to the HVAC noise.
  • Run the hot shower for 15 minutes and see what happens to the walls afterwards. Hygrometer would probably be useless - sensor has too much inertia.
  • If you feel particularly adventurous, you may even want to shut off the HVAC for a while and then switch it back on and see how it behaves. Keep in mind, though, that if it brings the temperature back no normal within 15-20 minutes, you have a unit that is actually oversized (unless it is multistage, which is very rare).
And, again, start paying attention.

Saturday, August 4, 2007

Google Calendar as external scheduler for DZ???

Just thinking aloud - would using Google Calendar API be a gross overkill or actually a smart idea?

Let me see...

  • Unlimited number of zones supported...
  • Unlimited number of periods scheduled...
  • Arbitrarily flexible scheduling - you want 5+2? We have it. You want 5+1+1? We have it. You want 7-Day? we have it, too.
  • Accessible from Internet...
  • Accessible from your mobile phone...
  • Relatively nice and user friendly user interface...
  • They even work on improving it while you sleep...
Actually, this may not be such a bad idea at all.

Thursday, August 2, 2007

Informal Review: Honeywell RTH7500

Honeywell RTH7500 Thermostat

Following up the RiteTemp GMPG808C review...

This thermostat is actually simpler to describe. It has no character. You don't notice it.

Actually, one might take it as a compliment - this is exactly what you want from an appliance - all you need of it is to perform its function and not struggle for getting a piece of your attention all day.

But it'll sure make you work to get to that point and will punish you if you try to upset the status quo.

First of all: don't lose the manual.

The rest of installation is simple - just follow the installation manual. It would be a good idea to read all of it beforehand - there's a couple of quirks you need to be aware of, in particular, configuring the thermostat to work with your exact HVAC system configuration.

Configuration takes a while - again, it's better to have the unit on the desk before you, and not in th wall cradle, when you do it. Can't do it without the manual - options are numeric. Did I mention - don't lose the manual?

That's basically it - unless you are really off with setpoints and schedules, you won't have to touch it again.

A few observations:

  • It is nice to be able to move period boundaries. Different people, different schedules.
  • You may want to think twice if you really want to use the "recovery" option (the one that makes sure that if you set the period starting at 9PM having setpoint of 78°F, you will have the room at 78°F at 9PM, instead of HVAC unit starting to struggle to cool it down at 9PM) - this option will throw a wrench into your energy savings if you are on a time of day usage plan. The worse is your HVAC (or, should I say, the more properly it is sized), the less useful this option is.
  • Have to imprint it in your mind that all you need to do to change the temperature temporarily is to press up/down arrows a few times. There is no need to press "hold" - this makes the thermostat hold the temperature forever. Kind of counterintuitive in the context of other interaction patterns - closure is expected, but missing.
  • I absolutely hate the fact that the only way to see the screen in the dark is to actually press the button, and, it does something just as you press the button.Watch what you're doing. The only way not to screw things up is to learn what button is idempotent when pressed twice, and find it in the dark (oh, by the way, it is not the temperature up/down arrows... they invoke a "temporary temperature change" context, which you have to explicitly get out of or let it time out - of course, not before the light goes off). Or just forget it and switch on the lights - to me, this option eventually won the argument. In other words, if you're specifically looking for a backlit LCD thermostat, have a chuckle and move on.
  • Summarizing the above, one could say that the user interface design violates the principle of least astonishment and thus may not be well suited to people who still have their VCRs blinking at 12:00.
  • There is no apparent way to adjust hysteresis, so if you are big on energy savings, you'd better consider thermostat that can do that - GMPG808C is not the worst other choice.
That's basically all. I can make an educated guess (but it is a guess nevertheless, please let me know if it is correct) that other thermostats of the same product line are probably identical to this except for different scheduling options:

  • RTH7500 supports 7-day programming (for $100);
  • RTH7400 supports 5-1-1- day programming (for $80);
  • RTH6300 supports 5-2 day programming (for $60);
  • RTH3100 doesn't support any programming at all (for $50).
Bottomline: brand name may be overrated and overpriced.

The only other consideration is - it's been less than a year since both Honeywell and Rite Temp thermostats have been installed, so let's see which one lives longer, and by how much.


SketchUp Sketches: DZ Testbed

This is a contraption that can be used to test the zoning controller functionality and operation. As the moment of writing (the image above is live, so is the link) it is just a rough draft (yeah, and it's 2:30AM), but I hope you get the idea. Plug heat sources (electric bulbs will do) into big holes. Plug temperature sensors into small holes. Connect the servos to DZ output. Connect fans to DZ output. Switch it on and watch it go crazy.

Four servos may represent up to four zones.
Four fans may represent up to four HVAC units.
Dimmers may be used to simulate variable heat load.
The divider between two middle fans is missing intentionally.
All sizes in the model (fans, servos, planes) are true and correct.

Link to the model page

Tuesday, July 31, 2007

SketchUp + HVAC-Calc = ?

Loosely quoted, "Good companies have many great ideas. Great companies know which great ideas to discard".

Alas, I will not have time to implement this, nor ways to approach the Big Guys to make this happen, but I wonder - am I the only one that sees an obvious symbiosis of SketchUp and HVAC-Calc?

Granted, it's not a five minute project, but all the necessary components are already there - and it won't be that difficult (especially for big guys like Google) to implement a real-time heat loss and gain recalculation as one works on the model of the house...

One of the most important features of SketchUp is that it, being a Google application, evolves fast. Plugins are there, too. It would be really interesting to see where it goes - SketckUp Blog is a nice place to keep an eye on it.

More on SketchUp later - it might have many obvious and not so obvious ramifications on the ways home automation, HVAC and general improvements are done. For example, the most obvious side effect of one creating a house model is that all the hidden spaces you've never thought about become obvious, and the task of routing your cable system becomes significantly less intimidating.

to be continued...

Sunday, July 29, 2007

Short take: two HVAC units vs. Zoning System

Talk about outsmarting oneself.

The whole point of The Dual Nightmare article was to convince the reader that there's no way two HVAC units can serve the house as good as one zoning system. Alas, the subject didn't click together with what people were looking for. Let's see if this one is better.

You will never buy a good zoning system, either

About a month ago I was trying to convince you that you will never buy a good HVAC unit. Today I'll try to hammer the last nail into the coffin.

Assumptions are a bit different in this case - if you are even investigating zoning systems, it means that the situation is pretty bad. Buckle up, it's about to get worse.

A slightly elaborated version of how DZ got actually started looks like this:

  • Existing systems were extremely dumb;
  • They were priced astronomically;
  • People who were selling them didn't have a clue;
  • People who were installing them knew just about as much, and, to add insult to injury, were actually afraid of zoning systems.
Situation hasn't changed much since -

Zoning systems are still dumb. Even the smartest ones are - the manufacturers haven't realized yet that they absolutely must play nice with other kids in the sandbox, and they keep producing proprietary components - yeah, I'd like to see the Carrier Infinity (a.k.a. Bryant Evolution) zoning system work with a pretty damn fine Lennox split unit that I have absolutely no motivation to replace or upgrade, it works just fine. My favorite pet peeve - none of them allow any real time diagnostics without special tools - what's the big deal, Ethernet and SNMP's been there forever. You'd think that with the price of chips going down so much, they'd have it in each and every unit, but no - there is just one, Carrier Infinity System Access Module - and even with that, the details on the version that allegedly supports Ethernet and wireless are very, very sketchy. Can't wait for it to come out.

The prices are still where they were.

Salespeople are still the same. Sometimes it is simply hilarious - see HVAC-Talk for the story of a Carrier dealer, out of all people, trying to talk the customer out of buying Infinity Zoning.

HVAC contractors have changed a bit - some of them did. Smart people hang out at HVAC-Talk, others are proudly proclaiming that they haven't heard of Internet and for sure don't need it to teach them how to do their job.

So, basically, it all boils down to the following:

  • If you don't do your homework, you're screwed - you will pay too much for something that is not going to ease your pain;
  • If you do your homework, you're screwed - what is out there is too dumb to ease your pain (up to 8 zones? forget it, I need twice as much, and why is it such a huge problem to begin with?);
  • If you compromise and buy what they sell you, you're screwed (read: Vendor lock-in).
So, what's the best way out of this? Don't buy a zoning system...

Or, you know, you could just make one...

Sunday, July 22, 2007

A/C Can't Keep Up?

Been there...

First of all, if that's the case (and not the phenomenons described in Thermostat Wars), it means that something is pretty much busted in your HVAC system.

Not necessarily the unit itself - ducts may leak, filter may be dirty (how many years ago did you change it last time?), you may have cut the trees on the southern side that provided you with shade and so on and so forth. Best bet would be to assess the overall system status - but that's going to cost you.

Next best assumption is - you don't have money not only to fix something if it is broken (1), but even to assess the status. Or, for some reason, this is not practical (say, the assessment, fix and/or upgrade is planned and budgeted, but the right time hasn't come yet). Well, this is not a nice situation to find yourself in, but not all hope is lost.

All the things below are pretty trivial in retrospect, but sometimes not obvious upfront, so I'm going to lay them out anyway.

First of all, set the thermostat to a lower temperature early in the morning and leave it there. Your house will store some energy and will help your A/C fight with the sun. You must realize this will somewhat increase your electric bill - but not much.

You probably heard that you can't run evaporative (a.k.a. swamp) cooler together with your other (known as refrigerating) A/C - the swamp cooler will be busy injecting humidity into the air, whereas refrigerating A/C will be busy removing it from there - thus adding $$$ to your electric bills and doing little else.

Also, be ready that the house will be significantly more difficult to cool some time after you stop using evaporative cooler - all that humidity it pumped in is still there, contained in the air, clothes, carpets, stuffed furniture and building frame.

Close all the blinds and shutters you have. If some of your windows don't have them, go buy some - they're relatively cheap and will significantly improve the insulation - not only they block the sun radiation, but also introduce insulating air pocket when closed.

Go get some insulation sheets from your favorite home supply store and stuff them between the shutters and windows - bad windows may contribute as high as a quarter of total heat load to the house.

Along the same lines, if you're planning to improve the house, don't go cheap on windows - get dual or triple pane tinted windows - and do your homework on selection. Makes the world of a difference - our upstairs bedroom on the south side of the house with good windows installed was significantly cooler than north facing rooms with old, single pane aluminum frame windows.

Make sure your ceiling fans work for you, not against you.

Well, that's just about it for starters...

In addition, there's a nice article about Tricks to Keep Your House Cool This Summer (except for the section about fans, which I disagree with) - and make sure you read the comments. Have to apply a good sanity filter to those, though...

(1) Having home warranty is relatively painless way of making sure this never happens; will cost you anywhere up from $250 a year, depending on the features - whether you have a pool, etc. - but it opens another can of worms altogether.

Saturday, July 21, 2007

Trivia: Not Web Surfing, Blog Hopping

Not that I just realized it, but it's just I have to conduct a lot of research recently, and it is now painfully obvious - the Web as it was before is dead. Static web sites are mostly either brochureware and therefore useless, or product, service or design specifications, or simply abandoned. All current information has shifted to blogs.

Search engines seem to have heed the trend - information contained in blogs is indexed significantly faster than static pages - I won't be surprised to discover that blog hosting sites have feeds to search engines that allow indexing in almost real time.

A corollary: good blog browsing tool is of paramount importance. Web browser is simply inadequate. RSS reader is better, but not much.


Friday, July 20, 2007

Short Take: Fractal Design

For years (I think, starting somewhere in 2000), I've been fighting my delusions of grandeur when explaining the concept of fractal design to people - I thought that obviously somebody must've thought of something this simple way before I did, and, hence, it is a common concept that I heard of somewhere and subliminally decided that I coined the term.

Apparently, not quite. Despite the fact that Google search for fractal design and fractal architecture returns more than enough matches, my patience was exhausted well before I could find anything similar to what I had in mind.

So let me put the stake in the ground, then, and introduce a definition:

Fractal Design: design pattern characterized by approximately same level of complexity at any level of abstraction.

It is a counterpoint to God Object (a.k.a. Blob), Interface Bloat, Spaghetti Code, abused Ravioli Code , Big Ball Of Mud and possibly other Antipatterns.

Starts making sense in context of Complexity Management, which, in turn, is not very well defined in the software engineering domain (this nice essay is just about the only article connecting the two), though, apparently, is widely accepted and practiced in business.

Short Take: Hysteresis in RTH7500

Frequently asked question with a very vague answer - what is the hysteresis (a.k.a. dead band) of my thermostat?

For Honeywell RTH7500, the measured (therefore not exact) typical value is about 1°C (about 1.8°F) - for the sensor located in the room behind the wall where the thermostat is.

Worst observed value is 2.5°C (about 6.3°F) - for the sensor located on the first floor (the thermostat is at the second) - this is not actually a property of the thermostat, but rather an indication of how badly the airflow was designed.

Another question - can hysteresis be controlled in RTH7500? The answer is: probably not.

If it can, there's no way to do it that is described in the documentation that is sold with the thermostat (yes, I found the manual, feel free to ask me what those numbers mean).

Wednesday, July 18, 2007

Honey, there are gremlins in the house!

Like the saying goes, "Flying is the Second Greatest Thrill Known To Man, the First is Landing".

The most thrilling part of getting into a new house is the first night. Or any night, for that matter, until the dust settles. It's the time when you find out with excitement that the people that sold you the house forgot to mention that the neighbor behind the southern fence likes to play his electric guitar off key at 5AM, or that the guys across the street get their truck that is older than me out of the garage and start fiddling with the engine and revving it at about 11PM... You get the picture.

Then, deeper into the night, you start hearing noises. The one I'm talking about drove me nuts for several months until I figured out what it was. It's quite rare (so far), because the only HVAC units affected by it are the ones that are slowly ramping up and down.

I'm taking about loud bangs in more or less rapid succession, seemingly all across the house. Gremlins.

Hindsight is always 20/20, and now that all the facts are laid out before you it is quite simple to see what it is: it's the flat tin panels that comprise the ducts flipping back and forth when the pressure changes, all of them at different times. What makes it fun is that the sound pattern changes as the building ages - panels that used to be well insulated and thus somehow dampened are not anymore because of the insulation breakdown, and the more time passes, the more pronounced the phenomenon becomes.

It is also an indication of the fact that the pressure in the ducts is quite high, probably way above what it should be.

The best part? There's probably nothing you can do without significant amount of money or elbow grease injections, so might as well get used to it.

Proper fix, though, assuming the pressure is within reason, is to apply sound dampening materials to the outside surface of the ducts. I guess the trick would be to find a material that sticks to the surface and doesn't let it bang, and at the same time won't break down for a long time.

There are also products called "acoustic duct liners", but knowing how widespread the problem of undersized ducts is, I would be extremely cautious stuffing anything alien into the ducts, unless you're absolutely sure the duct itself is grossly oversized.

Which returns us all the way back to the heat loss and gain (a.k.a. heat load) calculation, but that's a different story for a different time...

Short Take: Where's My RTH7500 Manual?

Exactly where you put it, dummy.

Correction: I am the dummy.

So here I am, trying to figure out the way to configure the hysteresis and, at the same time, save myself a long walk to the shelf at the second floor where I *think* I put the plastic bag with the manual and spare parts. Also, it's middle of the night, it's dark, the light switch is out of the way, everyone in the house is asleep and I don't want to step on the cat strategically placed somewhere down my path.

So I'm thinking: it's 2007, let's google it up.

Yeah, right.

I guess my patience is thinned by previous encounters with HVAC machinery and service, unlike one of this gentleman.

Mind you, all configuration settings in this thermostat are not described by words. They are described by numbers. There's no way in hell I can remember numbers I have to use once in a few months, if not years. And the paper manual is nowhere to be found. And what other companies usually put up (a printable PDF document) is nowhere to be found, either.


Another score for Rite Temp.

And don't lose your manual, otherwise you end up with a quite expensive brick on your wall.

Update: I've found the manual...

Tuesday, July 17, 2007

Rite Temp GPMG8085C: Informal Review

Rite Temp GPMG8085C

Who would've thought that this blog would be one of the most often referred to sources of information about GPMG8085C... All right, if that's what y'all want...

Ever heard of "The Golden Triangle"? "Good, Cheap, Fast - Pick Two". So, this thermostat may just as well be the closest approximation. $20 cheaper than the next guy (Honeywell RTH7500, I'll come back to it another time), does the same job, if not better.

Comparable quality and length of DIY installation.

Installation complexity: no-brainer (YMMV). A few advices, though:

  • Make sure you RTFM;
  • Don't drop the wires into the wall;
  • Programming is best done when the thermostat is laying on the desk before you, not when you're standing next to the wall with the thermostat on it;
  • At least for me, the preinstalled battery still works after a few months of operation, may want to ignore that paranoid advice to remove it.
Significantly bigger and nicer backlit touchscreen than the competition has (to be completely fair, they do have a big touchscreen on VisionPro, but that one is almost twice as expensive, so no cigar), and it has a nice textured button that you can grope (English experts, give me a non-ambiguous word and have my thanks in return) in the dark without being afraid to push a wrong button and reset something.

You have to really hate your customers not to provide an option like that (example: RTH7500 needs you to press any button, and, invokes the action corresponding to that button, even in the dark. So you have to be really careful where you tread, and the fact that the screen is backlit is useless - you can't comfortably use it anyway).

There's a stylus and a holder, but feel free to ignore it - fingers and/or fingernails do the job just fine. No visible scratch marks after few months of use.

7-day programmability is certainly nice, but the schedule selection is really weird - you can't set the schedule boundaries at arbitrary time, but only at one of two settings (forgot what times exactly, will update later). Kind of inconvenient, and this is probably the most annoying feature, or, rather, lack thereof. Competing device shines here - you can have your heat and cold any time.

Side note: I'm wondering why nobody figured yet that anticipation is something you're quite willing to have for a period starting, say, at 6PM, when you return from work, but not really want for the period starting, say, at 9PM - when you are on a time of day electric plan, which makes energy after 9PM three times cheaper than before. Remember, you read it here first.

If you don't need 7-day programming, there are other, cheaper Rite Temp models that offer compatible feature set, but 5+1+1 or 5+2 day programming.

I'm quite willing to forgive lack of schedule configurability for including an extremely important feature - you can manually change the hysteresis. Setting it to the maximum value makes the temperature spread quite noticeable (up to 5°F), but makes the unit cycle about three times less often than it would otherwise do. Don't have equipment to measure the actual gain, but would certainly recommend this thermostat to people who are either energy conscious and don't mind little discomfort, and to people who have grossly oversized units - you guys may suffer from temperature swings even worse, but at least your electric bill will drop like a rock because the unit won't breathe like a dog outdoors in Arizona summer anymore.

Can't say anything about humidistat - not much use for it in the middle of Arizona summer.

Another useful feature - filter usage counter. Depending on the climate, your unit may cease operating for a couple of months in mid-season, so you can afford to buy a higher quality, more expensive filter without a fear that you're wasting money (just think of how much it'll cost you to clean the inner coil when the time comes, and reconsider buying that inexpensive $3 filter).

You definitely need to read the manual provided with it in order to learn to operate - but then again, this is true about any more or less complicated home appliance - it takes significantly higher IQ to figure out how to connect the 5.1 home theater and the rest of components together without electrocuting oneself, so no big deal here.

At least all the settings have icons assigned to them, and you can figure out what is what, unlike some other designs, where features are indicated with numbers (come on, it's not 1960 anymore...)


Well worth the money I paid for it.


God, what have we come to... Anyway - use your common sense, don't do stupid things, and read this first.

Wednesday, July 11, 2007

DZ Live: July 11 2007 Presentation Draft

Below are links for the presentation happening later today:

Questions from the audience and answers to those questions may or may not be available later, depending on whether anybody is going to be transcribing the session (hint: if you want your question answered, this is the right place to post it).

Tuesday, July 10, 2007

Hardware Architecture: Centralized vs. Distributed

Hardware and software are the ying and yang of what modern appliances strive to be. Evolution and oscillations of the software part of DZ is tightly coupled to choices hardware offers.

At all times, cost was the predominant factor. $99 temperature sensor is not a valid choice for someone who is most likely using a mechanical thermostat, but $3 chip probably is.

So what that it doesn't have a nice box - rich and poor are affected by extreme temperatures in strikingly similar ways, and if you can't afford to cover the chip, and you had to staple the cables to the walls instead of paying couple of thousand dollars to the crew that hides them into the walls, so be it. At least, you're comfortable now.

Same goes for professionally installed dampers vs. DIY registers.

So all right, it is clear enough that $3 chip doesn't have a human interface. All the control was initially being provided through the debug console - sure, it was limited to whoever had the password and the inclination to fiddle with it, the rest of the family had it by the way of voicing opinions and complaining (which, surprisingly, ceased pretty soon after the system was activated).

But it is crystal clear that this solution doesn't stand a chance in the long run - in order to pass the SWMBO Compliance Certification, the system must have at least rudimentary controls in each zone (provided the zone is used often enough; it is unlikely that a server room is going to require much intervention often).

Which presents quite a few interesting options.

Rudimentary controls may or may not be terminally dumb.

The dumbest possible control will include a display (two 7-segment LED is just fine) and two buttons (which actually give you more than two possible inputs: you can use "both buttons depressed" as a signal to change the control context). Plain 7-segment LEDs, though, cross the border between "cheap as in inexpensive" and "cheap as in obnoxious" - a graphical LCD won't be that expensive today, especially given the fact that it will constitute just a fraction of the total cost.

Now, what difference does it make if you have two buttons or eight? Granted, two buttons is 4 times cheaper (by themselves), but again, much less so, given the infrastructure considerations: first of all, having 8 soft keys gives you unlimited flexibility for all practical considerations, second, they won't be that much more expensive compared to the total cost.

Does the sensor have to be in the same box as the LCD and the buttons? It depends. First of all, the box has to be located where it is convenient to access it - most probably, next to the light switch. But the sensor has to be located where the actual temperature has to be measured, and that is where the complaining person is - in the bed, at the coach, next to the oven, you name it. On the other hand, the complaining persons lived with a single thermostat for all their life, so even the sensor that is in the box is already going to be an improvement. Another consideration is that this case requires less wiring (assuming it's wired; wireless solutions are a whole different can of worms).

Yet another component is the servo controller. Historically, servo controllers were always centralized - one controller, bunch of wires, servo boosters and capacitors at each servo, good enough.

Later, Nic van der Walt provided schematics for distributed 1-Wire servo controller, which would support bang/bang dampers with no problems at all, and modulating dampers that will be quite noisy - latency of 1-Wire protocol with the bunch of sensors on it is insufficient to provide software controlled quiet transition.

Today, there are chips with PWM supported in hardware, and if they have enough brains to support even the simplest quiet transition possible, then you have the distributed servo controller right there and then.

Considerations above assumed we're ignoring existing 24V dampers (which are mostly bang-bang, and regardless of whether they are or not, they're well beyond the approved spending limit for the audience) and using R/C servos to control the dampers, as shown here.

This just about concludes the story. There are three major topics left uncovered - the HVAC actuators, hardware interface selection, and making all the gadgets wireless - but the article is getting too long, so stay tuned.

Monday, July 9, 2007

Thank you for using @#$%S...

Someone who's been through one major and one minor flood, heat pump compressor, four or five pool pump motors, couple of pool filter tanks, few dead refrigerators is not likely to treat warranty issues lightly. Thus, after being somewhat dissatisfied with service contractors taking a bit too long (up to three-four days) to show up, I decided to abandon my warranty company in favor of @#$%S, a big, domestically owned, reputable company. There is safety in numbers, I thought.

How naive of me.

Jumping ahead, I did go to extreme depths to explain to them that I have not one, not even two, but three units and did have to pay extra premium for the service.

Being diligent, I decided to use the service that's been advertised among other warranty clauses - preventive maintenance. So I call them up, they give me a window a couple of weeks later, it's still February, I'm thinking, what could go wrong...


Guys show up, take a look at the unit, say it's not on their record, spend half an hour on the phone with headquarters, say this unit is not on their records. I say fine, there's another one, which is on your records, go take care of that. They do, profusely apologize, and leave. I call up again and explain that the unit in question is not quite up to snuff and has to be looked up, they say sure, and schedule another appointment two weeks later.

No call, no show. With a window like 9 to 12 or 1 to 5, it's quite aggravating - half a day is wasted.

Another call, another two weeks. A crew arrives with gusto, steps up to the unit and says "Dude! This unit is not on our records!" as I stare at them in disbelief. So I make them write down the model and serial numbers of all HVAC equipment, upon completion of which task they notify me that I have not three, but five units, namely, one rooftop, two condensers and two air handlers. Fine, as long as the unit gets taken care of. They say they can't do anything now without headquarters approving, and leave.

Another hour on hold, another conversation, another two weeks. Another crew arrives. Guess what? The unit is still not on records.

Another hour on hold, another conversation, another two weeks. Another no call, no show.

I'm thinking, it's costing me too much aggravation already, the hell with it - if it breaks, they'll fix it. So I leave it alone.

So the summer comes. In June, one of my HVAC units goes dead (the one @#$%S "maintained"). I call @#$%S, they say it'll take them 9 (nine) days for them to dispatch the serviceman. I tell them this is unacceptable, keep biting their ankles every day - and 8 days later, the guy shows up. Replaces the fuse and is on his way. Not that I would believe that the fuse is the root cause, but there's nothing I can do with it - all in all, he's a professional...

Within two weeks, the unit is dead again, with the same symptoms. To make the long story short, it took them over a week to send someone over (mind you, we're talking about August in Phoenix), and the unit did get fixed. Ground short.

This is not a kind of service one pays premium for, so BBB complaint gets filed, processed, and somewhere in the middle of the winter a symbolic compensation comes. End of story.

Or so I thought.

What made me dig up this stinking corpse is that an appliance I bought a while ago, it turns out, has its warranty served by @#$%S. Damn, I say, let's hope it works this time.

Yeah, right.

Scheduled visit number one, 1 to 5 window. No call, no show. At 4:30 service center is called, and they are telling me that the contractor is actually parked in front of my house. Right. At 5:30 another call to service center, and they're told about the fact that contractor never made it in from the driveway, about pretty contemptible track record, of preexisting BBB complaint. They politely apologize and say they will have to call back reschedule.

A day passes. No call. Calling them. Another hold, another conversation, another 1 to 5 service window. Another no call, no show.

I wonder, are they brain dead? Okay, it may be fine to screw things up once. Not so okay, but happens twice in a row. But six??? And a complaint??? And, after that, two times in a row again?

Now, for those curious about the actual identity of the company... Pretty easy to figure out - I just want to leave myself some maneuvering space in case they ever get to read this and decide to send me a cease and desist. That would be fun to watch, though, and something tells me that I'm not the only one having this kind of experience. And have no doubts, another BBB complaint is on the way.

The most saddening thought? They're not alone. This winter, the unit I was trying to take care of in this story has finally died (pretty non-trivial failure, as it eventually turned out), and the contractor that was trying to fix it tried everything he could think of (took couple of weeks to order the parts, have them delivered, and another appointment scheduled), then just "recharged" the unit and said "Let's pray that it keeps working".

I guess he wasn't praying hard enough. But that's a different story for a different time.

DZ Live: Confirmed

As previously announced, a presentation tentatively named "DIY Zoning: 7 years down the road" will take place at Phoenix Java User's Group meeting on July 11 2007.

Look for schedule and site directions on PHXJUG site.

Does Open Source Pay Off?

Depends on who you're asking.

As you can see, big corporations are simply ecstatic with it. Why, you don't have to go through expensive interview and trial and error interview process, and all you have to do is to ask a candidate for the list of Open Source projects they are or have been involved in and then spend fifteen minutes googling the projects to figure out if the candidate is any good. Or, even simpler, just steal the idea and/or the implementation, if the project is obscure enough and your subject matter area is guaranteed to never see the public scrutiny. Within reasonable timeframe, that is - all you've gotta do is to generate profit that will allow to hire the best team of lawyers before the poor sod even realizes he's been ripped off. If ever.

As for the other side... It depends, again.

In almost 7 years since its inception, DZ Donations page at SourceForge generated sixteen dollars and spare change. Yes, you've read that right, sixteen dollars in seven years. Not to mean any disregard to people who made the donations (I will always remember each three of you by name), this is just about how much someone in my profession makes in time that it takes to smoke a cigarette without haste.

So, again, does it pay off? As you can see, not really. At least when you're observing the direct benefits.

As for indirect...

Companies hate to hire. They only hire if there's no other way to ease their pain. Every time they have to hire, they have to spend significant resources on recruiters in- or out-of-house, tear people away from work to conduct interviews, face uncertainty since there are so many clueless people familiar with software engineering shop talk that they penetrate the entry barriers fortified by recruiters with such ease, and given the fact the software engineering itself is not an exact science, but rather art - it may not even become obvious that someone flashing buzz words and certifications is a complete fool until much later...

But situation is becoming very different when there are cold, hard facts that you can present to your prospective employer. Because by giving them facts you are removing doubts and uncertainty and becoming a credible, verifiable and predictable asset (just think of the fact that more and more employers are starting to pay attention to your credit score).

Achievements in their immediate subject matter expertise area are the best for them (but not the best for you: you will be forced to sign the waiver basically making them own everything you and your parents have ever created, and your firstborn too - so you may want to talk to a lawyer and craft the "previous inventions clause" before you even start looking for a job).

Achievements in other subject areas, no matter how bizarre, do count, though you'd never know whether for or against :) Which brings another note to mind - you'll have to insist that recruiters include your extracurricular activities in their version of your resume that they send out to their contacts - because they may not possess enough expertise to see what is relevant and what is not.

Coming back to the original question, does Open Source pay off? Let me just ask you to visualize the idea of Linus Torvalds going unemployed and watch you laugh.

As for donations... Well, will someone tag a black Squeezebox or, even better, Transporter for me, please? Don't expect me to hold my breath, though...

Friday, July 6, 2007

Short Take: Modulating Dampers

A damper, in HVAC terminology, is an air valve used to regulate the flow of air through the duct.

There are two general kinds of dampers (definitions are probably not in line with HVAC terminology, but hopefully understandable enough):

  • Simple, also known as bang-bang, dampers - these can only be in fully open or fully closed position;
  • Modulating dampers are able to stay in any position between fully open and fully closed.

First kind is, of course, cheaper, but has serious drawbacks - first, the noise they make is quite noticeable (one can get used to it, though), second, they provide only limited control and are not suitable to advanced applications.

Modulating dampers, on the other hand, are silent by design and provide adequate control, but require more sophisticated control systems in order to utilize the capabilities.

Zoning For The Poor

Poor people pay more, it is often said. Let's see what would be an average cost of a DIY zoning system assembled out of components specifically intended for DIY applications. Let's make following assumptions:

  • We're dealing with an average family with two kids, geek parents who spend some time working home therefore four bedroom house (fourth bedroom being the office), two bathroom, dining room, family room, laundry room - total of 9 zones (that'll be a pessimistic estimate);
  • All the components will be bought through Smarthome;
  • Functionality will try to mimic what DZ offers today.
Let's see how much is this going to cost us at today's prices....

HVAC 4 Zone Controller - Rs485 - $349.99, power supply sold separately - that's just four zones, out of nine required;

Alternatively, HVAC 4-Zone Controller - $229.99, plus power supply - $11.99;

Thermostat Display Unit - $199.99, one per zone;

Or, as an alternative, wall mounted temperature sensor - $99.99 per zone, plus LCD Wall Display Unit - on sale for $107.99, for all four zones;

6-In Normally Open 24V AC Duct Damper or 6-In Normally Closed 24-VAC Damper- $59.99 (or, if you're feeling generous, 6 Inch Diameter Damper Normally Closed for low, low cost of $98.99 - I don't see much difference);

X10 Universal Module for $22.99 or Appliance Module for $34.99, depending on your configuration, one per damper;

Now, all the stuff above is just the beginning, but it'll be enough for a ballpark: the cheap version of the above for 4 zones will cost you, depending on components, anywhere between 973.86 and 1685.87 plus tax, shipping and handling.

For 9 zones (ignoring the fact that a 9 zone controller is not being sold, and counting only extra cost for dampers and sensors), the prices will be 1888.71 and 3355.72, respectively.

That is, not including cabling and insallation.

Oh, and that gives you only a bang-bang version using unreliable by design X10 protocol. Forget about remote control and monitoring.

For comparizon, DZ installation for the same physical configuration will cost you:

  • Anywhere from $50 for a beaten up 10 year old computer to $400 for a shiny new one to run the control system on (with web access, remote control and monitoring and unlimited number of zones);
  • Roughly $50 to $100 for 1-Wire adapter and servo controller, depending on source and capabilities;
  • $10 to $15 per zone plus some manual labor for modulating dampers;
  • About $3 a zone for a 1-Wire temperature sensor.
All of the above amounts to $152 to $552 for 4 zone system, and $217 to $617 for a 9 zone system (difference being primarily the price of the computer and servo controller).

Take your pick.

Update: Forgot to include cost of 1-Wire adapter and servo controller into DZ installation cost. Fixed.

Software Architecture: Centralized vs. Distributed

Evolution of software moves in mysterious ways. Especially if you're not the one contemplating it, but the one making it happen. Hindsight is always 20/20, and now that I'm looking back at the way DZ evolved, I'm seeing that I was merely trodding the same path as countless others - namely, coming all the way from monolithic single host software design to modular distributed.

Just as dinosaurs became extinct, DZ ceased to be a monolith even before it become public - the first GPL'd version was already split in several parts able to talk to each other via TCP/IP, and the parts were linked together in a modular container driven architecture.

Further down the road, the project started shedding more pieces as better versions of them arrived elsewhere (scheduler would be one example). It also became clear that as computers become smaller and cheaper, the day will come when it would be not only possible, but beneficial to utilize multiple computers for a task that could be perfectly done by just one - just for the very reason of having a particular computer in a convenient place for connecting hardware.

Most prominent examples would be -

  • An HTPC which has to reside in a rigidly defined place, next to the rest of AV equipment;
  • A wireless router that is a focal point of wireless and Ethernet connectivity;
  • A workstation, which by itself provides several relevant data streams (CPU temperature, motherboard temperature, hard drive temperature).
Which makes distributed communications difficult to underestimate. Initially, it was just about protocols, now, it's getting all about application interoperability and plugins (Cacti, Munin, Nagios, Mister House to name a few).

Stay tuned.

Wednesday, July 4, 2007

The Dual Nightmare

There is an ongoing heated discussion among homeowners and HVAC professionals about what solution to the problem of properly balancing the house is better - zoning the house, or having multiple units installed. There are all kinds of arguments on both sides.

The proponents of zoning are usually saying that it would be silly to use one switch to turn on or off all the lights in the whole house, whereas the opponents are pointing out that it is silly to pump the amount of air intended for all ducts together through one.

The opponents of zoning are usually saying that it is more reliable to have two simple HVAC units than it is to have one complicated HVAC unit and one complicated zoning system, whereas the proponents are pointing out that maybe HVAC professionals may be simply out of their depth and are trying to cover that up by silly arguments.

The opponents of zoning are saying that having two units is an adequate solution to the balancing problem and point out to the fact that existing commercial zoning systems are rarely extending "affordable" options beyond four zones, to which I say they are completely nuts and give the room (read: zone) count for three quite average houses that I've lived in: roughly 11 zones in Iowa farmhouse (2 levels, 4 bedrooms, full basement), 14 zones in one house in Arizona (3 levels, 4 bedrooms, game room, library) and 13 zones in the house I live in now (2 levels, 3 bedrooms). Oh, I do include bathrooms, too.

But I digress.

Sometimes you just have two units - for example, when you simply buy the house with them installed - it would be silly to rip them out, wouldn't it? So one just has to deal with it...

Whereas having two units is certainly nice, it is by no means a guarantee of any improvement whatsoever. Like it was pointed out before, all your luck depends on having the job done right.

Sometimes your luck is improved by the fact that the house was designed with heat exchange physics in mind (little heat transfer between floors, narrow staircases).

Sometimes it is degraded by the fact that aesthetic considerations took priority over common sense - wide open floor plans with walls being mostly glass, rooms spanning several floors vertically, and different floor count in different parts of the house.

Which is exactly the situation I have to deal with right now. The north side of the house (1 floor, 2 rooms + 2 bathrooms) is served by a nice powerful variable speed high SEER Lennox split unit. The south side (2 floors, 4 rooms + bathroom + kitchen + laundry room) is served by a puny rooftop Trane and a set of drinking straws they called ducts.

So let me skip the rant about how unthoughtful that was, and get directly to describing various interactions between two units that may happen. Let's assume for simplicity that we're talking about cooling season behavior.

Unhappy Load Meter

If both units kick in at the same time, and you are on a load controlled electrical billing plan, you're not gonna be happy. Neither is your electrical company, but that's a completely different story for a different time.

Cold Spots

It may happen that both units serve the same room[s], directly or indirectly, and the room has enough or more than enough supply and return capacity, and neither of the thermostats is in it. If both units kick in at the same time, the room will get uncomfortably cold.

Hot Spots

It may happen that the cold air supplied by unit A drags down the temperature at the thermostat controlling unit B. In this case, it will not get unhappy and cause unit B to switch on until unit A is off. Which will cause the rooms normally served by unit B to become uncomfortably hot.

The Skew

To add insult to injury, it is quite possible that the layout described above also makes unit A serve, at least partially, the zone that is supposed to be served by unit B - and in this case, unit A will keep running and running, possibly not even catching up with demand - and it will not get any help from unit B because the effect described above robbed unit B of necessary control input and is preventing it from switching on. You end up with one unit trying to do the work of two, for which it is clearly undersized. To further aggravate the situation, it is possible that the overworked unit will go beyond its normal design range, and then you have a dead unit (ask me how I know).

For more than one floor, The Skew is rather a rule than an exception.

Ask yourself a question, don't you always have to set the thermostat downstairs a couple of degrees lower than upstairs, otherwise it feels hot and stuffy? The scenario above explains it vividly. All there is is a leak of cold air from upstairs through the staircase (or a tall room) that causes the thermostat downstairs to make the unit stay off.


To prevent The Skew (further defined as one of the units working significantly longer than the other), you need to carefully balance the thermostats in such a way that the race never starts. This will usually mean that you will have one of the thermostat set below the comfort level, and the other above. Also, this is going to cost you, because the difference between "comfortable" and "balanced" positions of thermostats is going to make a significant contribution to your electric bill. Also, it robs you of comfort. Also, it will make you fiddle with controls all the time, unless you have monitoring set up, in which case you'll just spend half of the time fiddling.

It would be interesting to know what side of argument described at the beginning of the article you are now...