Turn thermostat down?

Yeah, that's one of the misconceptions the DOE is addressing with their notes to consumers. The other one, which I've heard a lot more, actually, is that shutting off your furnace for half of a day saves a half-day's worth of the energy you'd use if you kept the house at your usual temperature. That, too, is a big misconception.

Well, when this issue was hot some years ago, I measured the thermal time constant of my then house, which was built in 1896. The test is simple:

In the winter, heat house to 90 F, turn the boiler off, and record the declining temperature periodically. The time constant (to 1/e of temp difference between 90 and outside ambient temperature) was an hour or two, if memory serves.

So, for my then house, it made sense to reduce the temperature if one would be away for more than about 5 hours.

It turned out that the temperature decline curve was well described by a simple exponential curve, plotting as a straight line on log-linear paper. This implies that the thermal mass of the wall and ceiling plaster and to a lesser degree the wood floors dominated, and these swamped all the other thermal storage mechanisms.

Joe Gwinn

Veddy interesting. You must have a very determined curiosity. Although your house may be different from a typical house built more recently, it does give an idea about how long one has to reduce the temperature to make it worthwhile.

Well, I couldn't make head or tails of the then debate, and the measurement is pretty easy to make. The measurement times need not be evenly spaced, so long as one records the actual time each temperature is taken. The general pattern is to measure just before turning the heat off, after 10 minutes, after 20 minutes, after 40 minutes, after 80 minutes, and so on, each time measuring from the prior measurement time. This works because the rate of temperature change is fastest at first but soon slows. So long as one knows when the measurements were made, it doesn't really matter how well one follows the schedule.

Or, one can buy one of those USB temperature monitor/recorder units and use it to collect the data.

Excel is adequate to reduce the data, however generated.

So one can know exactly how one's house behaves, bringing the discussion out of the theoretical into the practical.

Joe Gwinn

I can identify with that kind of thinking, Jim, and especially with that attitude toward finding out things for oneself.

Let the Record show that Gunner Asch on or about Fri, 30 Oct 2009 02:39:09 -0700 did write/type or cause to appear in rec.crafts.metalworking the following:

Probably a good thing. I already have enough old flames too far away to keep me warm.

...who wants to live forever?

Well, I'd like to, live that is. "Life is a banquet! and most poor suckers are starving to death."

- pyotr filipivich We will drink no whiskey before its nine. It's eight fifty eight. Close enough!

Let the Record show that Larry Jaques on or about Fri, 30 Oct 2009 05:44:25 -0700 did write/type or cause to appear in rec.crafts.metalworking the following:

HA! You missed out on the Greatest Catastrophe known to man. But ... each to his own.

What confuses me, is how she, with that lovely layer of subcutaneous insulation, gets cold so easily.

Dames! Can't live with 'em, can live with 'em.

pyotr

- pyotr filipivich We will drink no whiskey before its nine. It's eight fifty eight. Close enough!

An accurate simulation is far more complex than any simple models using leaky buckets, capacitors or transmission lines. Building such a simulation that actually did show good correllation with observed (measured) behavior in a range of buildings and climates took some very competent senior engineers a couple of man years and a whole bunch of programming.

Let the Record show that Don Foreman on or about Fri, 30 Oct 2009 02:02:27 -0500 did write/type or cause to appear in rec.crafts.metalworking the following:

Which is why they go together: he's sweating, and she's getting the wet sheets.

"Please shut that door! It's warm in here, but I greatly fear You'll let in the cold and storm. Since I left Plumtree, down in Tennessee, It's the first time I've been warm."

pyotr

"And sometimes I wonder if they was, the awful things I done. And as I sit and the parson talks, expounding of the Law, I often think of poor old Bill--and how hard he was to saw."

- pyotr filipivich We will drink no whiskey before its nine. It's eight fifty eight. Close enough!

Let the Record show that Gunner Asch on or about Thu, 29 Oct 2009 21:49:26 -0700 did write/type or cause to appear in rec.crafts.metalworking the following:

LOL. A friend thought anything below 50 was arctic. So of course, she married and moved to Anchorage.

Then there was the lass who wore the long johns (top & bottoms) to bed, with the extra blankets on her side, while I stuck a leg out to keep cool. She came to bed all but shivering, and the first time I took her hands and said "warm yourself." Later, that could prove to be ... "entertaining" when I wasn't expecting it. But, "A Man's gotta do, what a Man's got to do."

- pyotr filipivich We will drink no whiskey before its nine. It's eight fifty eight. Close enough!

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Dan

Right. The transmission line analogy is a significant step closer than a capacitor and works well enough when one is working with something simple as a homogeneous mass surrounded by insulation. A house is not homogeneous and then there are other things as solar gain.

My current house has significant solar heat gain. On a sunny day the outside temperature can be about 40 degrees and the house will be comfortable with the furnace turned off. I take the window screens off in the Fall to maximize the solar heat gain.

Dan

I've long considered Eve as the world's first order of take out ribs.

Jeff

Let the Record show that "Stormin Mormon" on or about Thu, 29 Oct 2009

08:22:48 -0400 did write/type or cause to appear in rec.crafts.metalworking the following:

Now that we've thrashed out the heater thermostat setting, what about the hot water supply? I'm starting to think I seriously goofed when I got a new hot water tank, rather than go for an on demand system. I wonder how difficult it might be to retro-fit one into the kitchen, anyway? I might add, by way of explanation, I'm a single guy. That means I do the dishes every six weeks whether they need to be done or not, laundry when the pile on the floor is all dirty clothes, and shower only when I'm leaving the house. Not a lot of demand for hot water, on a daily basis.

- pyotr filipivich We will drink no whiskey before its nine. It's eight fifty eight. Close enough!

I've heard of 5 gal water heaters in RV, and trailers. I had

12 gal heater in one place I rented. Like you say, your water needs are minimal.

Did you install gas or electric? In either case, a "water heater blanket" is a good idea. More insulation.

If you read my Google Groups posting you'll see I did the same and found a cooldown rate of 2% - 3% of the in-out difference per hour, another way to state the exponential nature of Newton's Law of Cooling. I've also measured the heating rate, and I think that those two rates are enough to predict the likely savings for setback routines and let you select a good one before making lengthy measurements.

I don't have a multichannel temperature datalogger yet and recording only 10PM and 6AM temperatures doesn't catch a rapid temperature drop outside until clouds form and stop it, or how long the stove burns. During the day solar gain is an unknown. For my house I think it's equivalent to adding 10 - 15F to the outside air temperature.

Pyotr, you can reduce electric water heating cost with a tempering tank that effectively uses your main heating system to bring cold water to room temperature, or by shutting off the lower element to do the same internally. On my tank the non-adjustable upper quick- recovery thermostat heats to the right temp for a shower with no cold mixed in. My sink-spray shower hose limits demand enough that the element can keep up. Last month I used 33 KWH for showers and laundry (no solar hot water).

jsw

Never touch the stuff

The solar bump is noticeable. I could see it in phase stability plots when I was tracking the electrical length of a cable to picosecond precision for days. Could also see the boiler cycling on and off in the night.

One can get the little USB temp loggers for $50 to $100. Here is the successor to the one I have:

Joe Gwinn

snip

a water heater is a lot smaller than a house. It is inexpensive to insulate it very very well, so there is, even outside in a cold climate very little heat loss from the tank - and if it's inside in a cold climate, any heat loss goes to heating the house anyway. My understanding from people who live where a sweater is occasionally needed, is that the more serious concern is to plumb outside air to the firebox, so it doesn't take your warm inside air and send it up the chimney. Of course, if this is an electric, not gas heater, that does not apply.

If you don't feel a lot of warmth on the outside of the heater, you aren't loosing much energy

I looked into it a little bit when we replaced our heater a little while ago; the increased exhaust requirements were a killer in my house (hot water heater is located about dead center in my house, so there were going to be no shortcuts running the exhaust).

Let the Record show that "Stormin Mormon" on or about Sun, 1 Nov 2009

07:57:48 -0500 did write/type or cause to appear >>Now that we've thrashed out the heater thermostat setting,

My _hot_ water needs are minimal. Water for Coffee, OTOH, is the reason I laid in the supply of bottled water. Just In Case- a Case!

Electric. I think I'm out far enough that 'gas' means 'Propane.'

And a water heater blanket sounds good ... ("Strudelmeyer - write that down!")

pyotr

- pyotr filipivich We will drink no whiskey before its nine. It's eight fifty eight. Close enough!