Set Back Thermostat

tikigeorge · Post by **tikigeorge** » Sun. Jan. 06, 2013 7:01 pm

I have a Keystoker KA-6 boiler with three zones. Is it a good idea to use programmable stats? And if so how much change in temperature should I be using?

Post by **Rob R.** » Sun. Jan. 06, 2013 8:54 pm

I vote no. I have experimented with setback temps. and the savings was very small...but the cold floors in the morning were very noticeable.

lsayre · Post by **lsayre** » Sun. Jan. 06, 2013 9:04 pm

With coal I also vote no to the set-back thermostat idea.

BTW, that is a mighty fine looking boiler in your avatar!

Wiz · Post by **Wiz** » Sun. Jan. 06, 2013 9:07 pm

I'm with Rob on this, savings wouldn't be worthwhile. If your looking to save some coal, adjust red nut another turn out.

331camaro · Post by **331camaro** » Mon. Jan. 07, 2013 5:23 am

im another vote for no. set it and forget it

Townsend · Post by **Townsend** » Mon. Jan. 07, 2013 9:58 am

I concur as well. That is why I went with old style mercury T-Stat. Set it and forget it.

Post by **Rob R.** » Mon. Jan. 07, 2013 10:07 am

Townsend wrote:I concur as well. That is why I went with old style mercury T-Stat. Set it and forget it.

I see that you have it set above the "sweater" zone.

Townsend · Post by **Townsend** » Mon. Jan. 07, 2013 10:27 am

Rob R. wrote:
Townsend wrote:I concur as well. That is why I went with old style mercury T-Stat. Set it and forget it.
I see that you have it set above the "sweater" zone.

LMAO

Indeed!

Pacowy · Post by **Pacowy** » Mon. Jan. 07, 2013 1:35 pm

I'll vote yes. It's pretty much one of the laws of thermodynamics that your house will lose less heat if it is cooler relative to the outside (as it is during the setback period), so there should be some savings. In my case, my steam system will idle down to a fairly cool state, so my standby losses are reduced by letting it rest on the third shift. I set it back 3 degrees. On cold nights it often will run on a call for heat near the end of the setback period, so it's like an early wake-up call. As long as you end the setback period early enough that the system has time to bring things back to the daytime temp before you're up and about, there shouldn't be a comfort problem.

Mike

coalkirk · Post by **coalkirk** » Mon. Jan. 07, 2013 1:41 pm

Pacowy wrote:I'll vote yes. It's pretty much one of the laws of thermodynamics that your house will lose less heat if it is cooler relative to the outside (as it is during the setback period), so there should be some savings. In my case, my steam system will idle down to a fairly cool state, so my standby losses are reduced by letting it rest on the third shift. I set it back 3 degrees. On cold nights it often will run on a call for heat near the end of the setback period, so it's like an early wake-up call. As long as you end the setback period early enough that the system has time to bring things back to the daytime temp before you're up and about, there shouldn't be a comfort problem.

Mike

Huh? May be a law of thermodynamics but the law of common sense says as your house loses heat, it gets cooler if you don't replace it. I'll vote no. Set back thermostats were invented to reduce the cost of using fuels that are expensive. Coal is still very cheap! One of the big advantages of coal is that you can keep your house a nice comforatble even temperature without all the high cost. I'll vote no again.

Pacowy · Post by **Pacowy** » Mon. Jan. 07, 2013 2:17 pm

For all of the deference that is given to heat loss computations on the forum, I'm a little surprised that so many people dismiss the proposition that heat loss is proportional to the temperature differential. If it's not proportional, it seems like we could all keep our houses warmer than we already do without burning any more fuel. All else equal, if it's 20 degrees out, more BTU's are lost if the house is kept at 70 deg rather than, say, 65 deg. Yes, the system has to run to heat things back up; this is offset by the period at the end of the day when you can turn the system down but still have the house be warm.

I'm not saying everyone should use a setback thermostat, but I don't think it's accurate to assume that there would be no savings.

Mike

Post by **Rob R.** » Mon. Jan. 07, 2013 2:59 pm

Rob R. wrote:I vote no. I have experimented with setback temps. and the savings was very small...but the cold floors in the morning were very noticeable.

I should have been more specific. In my particular house a 2-3 degree setback resulted in small savings, and a larger setback resulted in long recovery times and a decrease in comfort that I didn't think was worth the amount of coal saved.

Mike is correct that the smaller the delta between the indoor and outdoor temps (isn't that the basis of a degree day?), the lower the heat loss. I think the best case for setback savings is a house that cools quickly, and has a high-output heating system that can quickly recover the temperature if desired. Such a home would quickly benefit from the reduced temp. setpoint, and the long burn required to get back up to speed might product better combustion efficiency than just banging on/off all day to maintain temp....that was the case for my house when it had leaky windows and was headed with an oversized oil boiler.

Can I change my vote to "it depends"?

Yanche · Post by **Yanche** » Mon. Jan. 07, 2013 3:01 pm

The goal of all of us is comfort with economy. Yes, lowering the temperature set point will use less fuel, but getting the living space back to the desired comfort point is highly dependent on your equipment. Clearly it's going to be working harder during the time it's trying to raise the temperature. How costly operating your heating appliance that way vs. just leaving it at a set is highly dependent the appliance. Typically instant on-off fuel type heating systems can save money. Coal appliances are not of the that type. What can save some money is an outdoor reset stoker boiler aquastat. This device changes the boiler water temperature based on outdoor temperature. For coal fired boilers the savings is generally not worth the cost of the instrument. Just change the standard aquastat set point manually a couple of times during the heating season.

tikigeorge · Post by **tikigeorge** » Mon. Jan. 07, 2013 8:11 pm

Very interesting, thanks to all!

fuccillo111 · Post by **fuccillo111** » Fri. Jan. 11, 2013 2:33 pm

maybe this will help. I made a marker on my hopper indicating a hight full level and a marker indicating a low level. from the low level to the high level was exactly 120lbs of rice coal. with outdoor temps very very consistant, I set my dig themo at 72 deg, in 48 hrs my coal level went from the high marker to the low marker, indicating that in that 48hr time frame I burned 120 lbs of coal. now, I filled back up to the high marker and set my dig thermo to this: 3:30am-6:30am=74deg, 6:30am-3pm=62deg, 3pm- 7:30pm=74deg 7:30pm-3:30a=68deg. with this schedule I was surprised that the level of coal had dropped to the low marker almost to the same hour that it had dropped with leaving the temp at 72. I stress again the day/night temps where very much identical. logic tells me the way to burn less coal is to lower temps thus reducing need to burn coal. like with fuel oil, ones not burning ANY if my themo is set to 62 and the house temp never drops to 62 during the work day. if you leave the house and its 70 in the house and it drops to say 64 during a 8hr work day you didnt burn oil as it never called for it. the question is then in order to get temps back to "70" you have to burn more to get from "64 to 70". I see it as a wash for my house, area, set up etc. either way coal is better than oil

Set Back Thermostat

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