Lost Electricity -2

[CJT]

Well said.

[CJT]

Which law of thermodynamics is contradicted, and in what manner?

[dpb]

...

Even if so (and I think it would take a pretty exceptional house design for it to make any discernible difference in any practical sense), it will certainly be more expensive and the time to reach the initial setpoint is still the same so at best it's a period after that initial warmup at most that can be affected at all.

[Ecnerwal]

Not true for at least 1 version of mechanical and 1 (probably many) versions of electronic thermostats, which have means of compensating for overshoot, and therefore switch at differing points under differing conditions. Said adjustments are often out of whack if ignorant persons mess with a thermostat they don't understand the subtleties of, or install a new one without reading the directions. Thus the automatic adjustment that someone else mentioned for a newer electronic 'stat.

[CJT]

I don't see why, unless you've got a heat pump with resistive backup.

First order, you need to put the same BTUs in either way to start the same mass at the same temp and end it at the same temp (although I will admit to the fact that the path can have a small effect due to the variation in delta-T's to the outside which affects losses along the way, but work with me here and assume that the heat needed to go from cold to warm is most of the energy used and that losses during the short time involved are second-order).

and the time to reach the initial

[dpb]

...

Because the input to reach the higher setpoint will also have higher proportional losses owing to the higher delta-T to the outside.

--

[CJT]

Sure, and I recognized that (in the part you snipped), but I think it's small relative to the heat required to heat up the house and everything in it.

[dpb]

But, it's as real as the heat going into the material is and at higher dT the loss proportion goes up at the same rate as the gain portion so you can't win -- you might come close to breaking even, but you can't win. Well, actually I guess you could possibly break even in one specific instance but it would take really detailed measurements or calculations to come to that point--if you were to be able to find the time at which the exterior wall temperatures would first reach their steady-state temperature and cut the extra input at the time when the heat input on the inside surface would then be transferred to reach that exterior temperature, then it would be the break-even point. Once the interior temperature is higher than that, then the exterior temperature also would rise above its steady-state value and then the previous conclusion would also hold.

The point in my view is that the two paths are identical owing to the fixed input until the lower setpoint is reached so there's absolutely no advantage there. The only question is whether then raising the temperature above the end setpoint perhaps aids a little _from that point_ in "creature comfort" -- my opinion is that unless the house is one that is actually designed as a thermal mass rather than conventional likely to be essentially unchanged although it just might aid a little bit in "taking the chill" off in comfort level. But it can't help but be more energy-costly and can't help the initial recovery.

[Mike]

Faver" >save time. But, the heat loss out the windows will be greater with a temp

That's the problem with using deg F, it bears no relation to reality :)

[Mike]

How quaint. You're obviously American.

The rest of the planet understands thermostats.

[Elmo]

Methinks you exaggerate. I've seen places in other countries where the people live in unheated buildings. I'm reasonably certain some of them don't understand thermostats.

[Mark Lloyd]

That is what HAPPENED (defective or not). How is reality meaningless? Are you saying it is now impossible for thermostats to be defective?

[Mark Lloyd]

I don't remember the brand, but it defiantly did use a mercury switch. This happened around 1974.

Still it made no sense to call it meaningless.

[daestrom]

Actually, the classic heating thermostat anticipator is a tiny heater that warms the sensing element a degree or two above the room's air temperature. The purpose is to cause the burner of the furnace to shut off just before the room reaches the desired temperature. This works because even after the burner shuts off, the heat-exchanger in the furnace and the blower continue to supply heat to the room for close to a minute longer. When properly adjusted, the burner will shut off just before the room air reaches the setpoint and the stored heat in the hot heat exchanger will continue and the room temperature will 'coast' up to the setpoint just as the blower shuts off.

This feature avoids an overshoot of the room temperature, but doesn't do anything to '...reduce the time needed to bring the room up to normal.'

daestrom

[Mark Lloyd]

Even if it has been turning the furnace off too soon, requiring the user to wait for another heat cycle?

[Mark Lloyd]

I didn't know about the heat anticipator 30 years ago, when I noticed the problem.

It was a case of the heat anticipator affecting 'the time needed to bring the room up to normal.'

[Duane C. Johnson]

Then you adjust the antisipator so it doesn't. It's relativly easy to do.

Duane