thermostat setback

Kevin_in_Denver_2

Steve,

"with 10:30 pm setback to 6am I use much more to recover than I save in 5 hours of setback."

If this is really true, it must mean that the boiler efficiency is significantly lower during the morning recovery. Possible I guess, but not likely. Definitely not half as efficient as you stated: "My gas consumption was twice roughly last year's October for a milder month."

bob_60

I have an older hot water radiator system with a boiler installed in 1989. Is a set back thermostat going to improve on fuel savings or will it cause the boiler to use more fuel to reheat the cold water and raise the tempeerature in the house. I've been told that keeping the heat constant in this type of system saves fuel. Yes or No? Thanks.

Mike T., Swampeast MO

Hate to say, but it depends on the heat loss characteristics of the structure, the amount of setback, the length of setback and the weather.

Programmable thermostats with a resettable "run-time" "filter replacement reminder" feature offer the ability to truly find the difference. Such will however require time, attention and fairly simple adjustments based on heating load (degree days).

Tom R.

Thermostst setback

Lowering the setpoint will ALWAYS save fuel. (Heat flow is directly proportionate to the difference in temperature) .The problem is finding the space temperature that the boiler can recover from in a reasonable time. Find a thermostat with outside temperature input to alter the start time according to weather.

Mike T., Swampeast MO

Lowering the setpoint will ALWAYS save fuel.

I must disagree.

Maintaining a lowered setpoint for a sufficient period of time will ALWAYS save fuel.

There's a BIG difference between the two and the "sufficient period" is relative to the structure, the heat source, the heat emitters, the mean radiant temperature and the room temperature settings required for the comfort of the occupants.

jeff_51

Have to agree with Mike on this one

The general rule is that it takes about 10hrs to break even on a setback stat. That of course is general and has many variables not taken in to account. I set mine at 68 and leave it. An outdoor controller to adjust water temp is in my opinion a good idea in your case, course I'm not there looking at your system either. If it is a single zone system, you might try constant circulation, won't save money, but flattens out the heat curve.

Spudwrench

setbacks

I was part of a setback thread here a while back...the consensus seems to be that that the savings tend to be small or negative. One thing I'm still left wondering about is why gas utilities and the D.O.E. promote nightime setback as an energy conservation measure if it is ineffective? Is it just too complicated to explain the various variables to the masses? (I gather that setback is more effective in a stick built house with forced hot air than a masonry building with massive CI radiators, etc...and it seems like there are more homes which fall into the "stick-built, FHA" category than the "massive building with slow responding heating system category"...so perhaps the utilities and DOE are just making a statement which is correct for the majority of houses? I'd be interested to hear opinions on this one...

Nathan

bob young

utilities

the utilities and oil companies want you to use as much fuel as is humanly possible. they could care less about anything else. money is their GOD.

Mike T., Swampeast MO

The DOE recommendations have changed a bit. They now recommend the deepest setbacks during the day with about half the daytime amount at night. Kind of odd to me considering daytime solar gains and warmer temps will limit heat losses compared to nights.

The "old" recommendations seem to have come from the 70s energy crisis. Makers of setback thermostats and other devices have latched on to those numbers as they show the highest potential for savings.

Those people with the least means (likely living in older, poorly insulated and leaky homes) do have the most to gain with rather deep, daily setback(s). Those with "better" homes have little or nothing to loose, but they're likely gaining much less than they are lead to believe.

Have noticed a number of homeowners recently commenting that while they set back deeply at night that the house never falls to the setback temperature. In that case USE LESS SETBACK and you'll likely be able to be just as comfortable at a slightly lower "normal" temperature than you are accustomed to.

Setback of unused spaces is an absolute no-brainer as is continually lowered temp in occupied spaces.

Steve_35

Setbacks

I'm definitely NOT an advocate of setbacks with hydronic systems. We get way too many no heat calls the morning after a very cold night from folks that utilize setbacks.

And let's say your heating bill is $2k a year. If you could save 5% and I believe that's a big if, that's $100 a year. Put that against the possibility of a frozen pipe and the discomfort in your home and is it really worth it? I guess everyone has to decide for themselves.

I think the money is better spent on caulking, insulation, etc. Maintain your comfort, reduce the possibility of a froze pipe AND save some money.

jp_2

forget the DOE

easy to figure out.
house has two sets of data. one, btu's to keep tstat happy and two, btu's to raise house 1 degree F, which is then dependant on the houses mass.

take a bored saturday afternoon on a cloudy day of consistant temp.

general idea:


1.) clock the meter for an hour. measure house temp.

2.) lower tstat all the way, let house drift for an hour

3.) set tstat at new lower temp, clock meter for an hour

4.) raise tstat back to orginal set point, clock meter and set your watch.

1.) this would give an idea of heatload at days temp,
3.) heatload at lower temp
4.) amount of heat needed to raise houses temp. #4 is tricky, you need to figure 'when' house has actually stabilized at orginal temp. not an impossible feat.

this is not a perfect test, but you'll get better answers than from your neighbor or the DOE.

Jaitch

Savings is sometimes a state of mind

While I don't personally feel that anyone anywhere is going to save a great amount of energy with a setback t'stat, some of my customers feel that if the house is a little chillier at certain times, then they have done all they can to conserve with a setback stat. I don't very often recommend them, but if the customer insists - even after my presentation - then so be it.....

JAITCH

Steve D_7

setback

I just replaced a difficult to program thermostat with a vision pro. The new stat was so easy to program and fun that I just had to put setbacks in at night and during the day.

Well, I was guaranteeing that twice a day the boiler would have to run long enough to raise the temp of the whole house 5 degrees. My gas consumption was twice roughly last year's October for a milder month. I am back to pretty even temps and have movements of 2 degrees still in the program. Checking the meter every few days shows that the burn rate is down but I am waiting to get the full month to see.

I expect that I will end up with 1 temp setting and no program just as I had before. As a poster has mentioned, the setback time is important and with 10:30 pm setback to 6am I use much more to recover than I save in 5 hours of setback.

Steve