Dilbert Creator Weighs In

Scott Adams wrote an article called How I (Almost) Saved the Earth.

If you care to read and see through the usual Dilbert language, there are quite a few good advices on what and how to do (and not to do).

(Image: Wall Street Journal)

Not Quite Competition: What Other Geeks Do

A pretty long article comes with the picture. The device resolves as Programmable Communicating Thermostat. Just like with ENV-VST-C, California Title 24 is mentioned.

They call the interface simple, but I think it recembles the DZ1 interface (scroll down a bit to find it, it has an unmistakably mainframe feel to it).

Whereas other manufacturers loudly proclaim "money saving features" with pretty vague claims of "up to" "if used correctly", I have a gut feeling that this device does indeed have an emphasis on actual energy conservation.

(Image: Physorg)

Bump: Green Dryer

There's been a comment on Green Dryer post that y'all might like:

You can find a nice version of this along with a custom base that raises the height of the dryer at:

http://www.heat-helper.com/

Thanks, Owen. Good timing, too - winter is coming.

First thing I would be concerned about before you reach for your wallet, though, is the smell that will get in if you're using scented sheets in your dryer. It is not really noticeable inside of the house, but I can tell you that if you walk down the street when someone's dryer is working, you can smell it from over a hundred feet away.

An easy test for that would be to move your drier away from the wall, disconnect the air hose and turn it on like you usually do - you'll know right away whether you'd be willing to tolerate that smell in the house or not.

Another consideration is that there will be some heat dissipation that you don't need during hot summer months. Relatively easy to deal with - it's not that big of a deal to reach behind the dryer and reconnect the hose directly to the dryer vent, especially keeping in mind that you have to clean that space couple of times a year anyway.

If that's the case, though, then I wonder why not just simply disconnect the hose from the dryer and let it be.

And, last but not least, the amount of lint and debris that comes out of the dryer is significant even with the stock dryer filter in place and cleaned before each run - if you're allergic, you might think twice about directing exhaust air into the house.

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.

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.

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.

Shut off the A/C or leave it running?

One of the most frequently asked questions is "Should I shut off my A/C when leaving the house, or leave it running?"

You see, it's not that simple...

This is one of those classical cans of worms that a lot of people (HVAC professionals in particular) have an opinion on, but just try to ask them to quantify the problem, and the result has all the chances to be hilarious.

Suppose, you go on vacation and shut off the A/C for a month. You've just saved a lot of money, except now you have to repair the cracked deck in your sixty thousand dollars Steinway grand piano you absolutely forgot about.

Suppose, you get out to walk the dog and shut off the A/C. I will call you paranoid and probably pound foolish, penny wise (all in all, having a dog is an expense you don't really have to incur if you're so concerned about your financial well being).

Suppose, you send the kids to school and go to work at 0800. Kids get back from school at 1400, you get back at 1800. This is where things get interesting.

Pretend the house is a pool. The HVAC is the hose. The walls are the drain. The drain is constantly open. The hose is open as it is needed to keep the pool filled up.

So when you shut off the hose, the pool starts losing water. The longer the hose is shut off, the more water you have to replenish (note that this is pretty much like cooling the house - yes, there will be a point beyond which all the water is gone, and from that moment on you're purely saving money). On the other hand, the longer the hose is shut off, the less you pay.

When you come back and open the hose, the water level goes up (and the house cools down). The bigger the hose is, the faster it will happen.

In other words, the bigger your HVAC is, the more sense it makes to shut it off or adjust the setpoint when leaving the house.

But wait, this is not the end of the story yet...

The drain is nonlinear.
The hose is nonlinear.

The hotter it is, the bigger is the drain, the sooner the water is gone.
The hotter it is, the more strain is put onto the hose (this is even worse for heat pumps in heating mode, because of the balance point).
It may lead to a situation when the inflow can't keep up with the outflow.


In other words, the smaller (or worse) is your HVAC, the less sense it makes to shut it off or adjust the setpoint when leaving the house. If this is your case, bite the bullet and pay the bill. Which reminds me, by the way, that poor people pay more.

But wait, this is not the end of the story either.

The highlighted cases above are for extremes. As the weather gets milder, efficiency considerations fade because the drain narrows (not as much heat is lost or gained). For this case, the longer you are away, the more sense it makes to shut off the HVAC or adjust the setpoint.

Now, let's remember the rule: whatever you cannot measure, you cannot improve. You may spend days and nights guessing, but you will never know whether you improved the situation or made it worse until and unless you have long term trends monitoring set up.

Which brings us all the way back, right here.

PS: Inquisitive readers will notice quite a few threads dangling here. Detailed explanations will go well beyond the point of loss of interest, but those who care to find out have probably figured out where to go to get the answers.