Showing posts with label surprise. Show all posts
Showing posts with label surprise. Show all posts

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.

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, 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.

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...)

Bottomline

Well worth the money I paid for it.

Disclaimer

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

Saturday, June 30, 2007

Short Take: Unlikely Contender?

Bryant, out of all things, comes out with a zoning system? Interesting... From what I gather, Bryant was always considered to be the low end counterpart for Carrier, just like in Toyota/Lexus and Honda/Acura relationships. And now, the zoning system?

Oh wait, maybe Carrier Infinity was a bit overpriced...

Update Jul 1 2007: Same thing, different branding.