Principles of Heating

 
ColdHouse
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Post by ColdHouse » Wed. Jan. 25, 2023 8:10 am

I would think there are principles that pertain to heating regardless of fuel used. Anybody willing to chime in?

1. Less energy used to maintain a steady temperature than to heat a cooled space. Setback thermostats might not be energy saving devices.

2??


 
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Rob R.
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Post by Rob R. » Wed. Jan. 25, 2023 8:26 am

ColdHouse wrote:
Wed. Jan. 25, 2023 8:10 am
1. Less energy used to maintain a steady temperature than to heat a cooled space. Setback thermostats might not be energy saving devices.
Do you mean it takes less energy to keep a space at a fixed temperature than to reduce the temperature for a period of time? That is false. Many people don't think it is "worth it" due to impacts to comfort, but the savings of setbacks has been well studied. We have also had some good discussions on this in the past:

Reducing Thermostat When Not Home
Room Temp Setback Poll

2. The greater the difference in temperature between the outdoors and interior of your house, the more energy it takes to maintain the interior temperature. This is why setback work...by reducing the average temperature of the interior of the house.

3. Every fuel burning heating appliance has an efficiency curve. Ideally the appliance will be sized so that it runs in the optimal range for much of the heating season. i.e. You don't want a stove that has to run at an idle all winter, nor one that must run wide open.

 
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Post by ColdHouse » Wed. Jan. 25, 2023 9:17 am

Rob R. wrote:
Wed. Jan. 25, 2023 8:26 am
Do you mean it takes less energy to keep a space at a fixed temperature than to reduce the temperature for a period of time? That is false. Many people don't think it is "worth it" due to impacts to comfort, but the savings of setbacks has been well studied. We have also had some good discussions on this in the past:
I am no expert and pretty much question most things. I do not doubt the information you provide but would still question it.

I heated with oil and kept the thermostat at 58* from 7:30 am to 4pm and from 9pm to 5am. The boiler was totally shut down via timer so as to not cycle when heat was not being called for. When that boiler came on it ran. The thermostat was set for 70 when not at 58. There were so many hours of 58 that the hot air when blowing never heated the mass even when the thermostat was satisfied. Boiler even during summer would cycle several times per hour to maintain temperature, thus the timer to shut it down. I won't say I didn't minimize my oil consumption because I am sure I did but I never had a warm house even when the thermostat was satisfied.

Regarding coal. As mentioned I am no expert. We had that arctic blast a few weeks back. I opened up my ash pan vents and had that stove producing some serious heat. However indoor temperature was at best 73* at the place it gets measured. One stove is in a fireplace the other exact same stove sitting atop a few bricks in an open space. The open stove has a stove pipe. When vents are open wider the stack stove pipe temperature is much hotter than when restricted. At that time I was consuming 100# per stove per day. Nighttime Outdoor temperatures were in single digits. Sure seems like when stove burning that much fuel there is more heat lost up the chimney.

Daily highs below 40 lows hovering at 30 stove idling and consuming about 25 pounds per day each indoor temperature hovering at 70. Stove pipe cool enough to put hand on. Secondary air cracked slightly. Shake, close ash pan door and fill hopper. Couple days ago FIL left attached garage door open for several hours. House went down to 64. I didn't touch the stove and waited to see what it would be like in the morning. Still 64.

It seems to me if burning a hotter stove results in more heat up the chimney and needing to stoke up the fire is required to heat up a chilled house, there would be wasted fuel going up the chimney.

As mentioned I am no expert and do not claim to know what I am talking about. I am simply sharing the details of objective data. I believe that there is a lot of energy required to quickly heat a structure and I don't think coal is designed for fast heat. Maybe a rice burning stoker might be different than an hand fired nut burning stove. Regardless I welcome the next arctic blast. The open garage door stimulates my curiosity. That garage is almost 1,000 square feet and the temperature in there has been above freezing and below 40. Obviously the fireplace stove and vaulted ceiling fan was encouraging that garage cold air to enter the home. My guess is an arctic blast wouldn't affect my indoor temperature any more severely than that influx of unheated air from the garage. I am guessing that if we endure a little cooler indoor temperature during an arctic freeze and barely change the stove and keep the home warm, very little wasted heat will go out of the house.

Thanks.

 
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Post by ColdHouse » Wed. Jan. 25, 2023 9:24 am

Some people drive from stop sign to stop light with their foot either on the gas or brake. I use as little fuel and brake as possible. There is no need to go fast only to have to stop. When towing a huge load, if your tow vehicle is capable of going 80 with that load over a mountain pass, is that the most efficient use of the fuel? Does cruise control save fuel? I don' think so when I use it I listen to the engine and it seems like the fuel is getting gobbled up or the transmission is kicking in to slow the vehicle down. A gentle foot on the accelerator that lets the vehicle gain a little speed on the downhill and doesn't punch it on the uphill seems more economical.

 
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Post by Hoytman » Wed. Jan. 25, 2023 9:26 am

Takes more energy to get back to a temperature...especially if it falls way below target temperature than it does to maintain a target temperature. That's my story and I'm sticking to it.

In my opinion there is a vast difference in "feel" of a room, or "comfort" of a room between a home heated with convection, or forced air, and radiant heat that actually warms objects in the room.

Does it take more energy (fuel) from my fuel oil furnace to keep my home at 70- degrees than my coal stove? Unequivocally, YES!! Forget the fuel comparison calculator! Why?

I use 1.5 ton of coal a year...and using the calculator it says I will need so many gallons of fuel oil...and I'm way, way, WAY above that. Regardless of the reason why it doesn't compute.

I can show you bills (cost and fuel use) to keep my home 68 degrees, let alone 70 (coal is higher house temp at 72-74 where ever I decide & 1.5 ton/yr usage), versus my coal usage at a constant...and remember the fuel oil is intermittent.

So I disagree. I don't buy that...at least for my situation...because I've run the numbers here. This coal stove is actually more accurate with it's thermostat than my furnace is with it's thermostat...meaning the stove maintains a better constant home temperature AND uses less fuel by comparison.

With my furnace the house temperature drops like a rock...and the furnace cycles often. Takes more energy to get the house back up to temperature than it does to maintain it. Although, I'm sure there is a certain temperature where this is false. Below that threshold I think it's quite possible.

"With my furnace the house temperature drops like a rock...and the furnace cycles often." Why does this happen? Cold air infiltration.

You get the same cold air infiltration using a stove, but the envelope of the house is warmed with a blanket of radiant heat as well as other objects inside the home...everything becomes a heat sink and actually...gives back some...requiring less energy once things stabilize inside the home.

 
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Post by Rob R. » Wed. Jan. 25, 2023 9:58 am

I heated with oil and kept the thermostat at 58* from 7:30 am to 4pm and from 9pm to 5am. The boiler was totally shut down via timer so as to not cycle when heat was not being called for. When that boiler came on it ran. The thermostat was set for 70 when not at 58. There were so many hours of 58 that the hot air when blowing never heated the mass even when the thermostat was satisfied. Boiler even during summer would cycle several times per hour to maintain temperature, thus the timer to shut it down. I won't say I didn't minimize my oil consumption because I am sure I did but I never had a warm house even when the thermostat was satisfied.
What you just described is what I referred to as "Many people don't think it is "worth it" due to impacts to comfort". You don't like the way a 70F air temperature feels with 58F objects in the room, that is completely understandable. It also depends on what type of system you are heating the house with. Trying to utilize temperature setbacks with hand-fired equipment will not be as easy as a stoker that uses a programmable thermostat.
Takes more energy to get back to a temperature...especially if it falls way below target temperature than it does to maintain a target temperature. That's my story and I'm sticking to it.
If you let your car idle overnight so it is toasty in the morning, did you save fuel ?

 
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Post by ColdHouse » Wed. Jan. 25, 2023 10:34 am

Rob R. wrote:
Wed. Jan. 25, 2023 9:58 am
What you just described is what I referred to as "Many people don't think it is "worth it" due to impacts to comfort". You don't like the way a 70F air temperature feels with 58F objects in the room, that is completely understandable. It also depends on what type of system you are heating the house with. Trying to utilize temperature setbacks with hand-fired equipment will not be as easy as a stoker that uses a programmable thermostat.



If you let your car idle overnight so it is toasty in the morning, did you save fuel ?
Does a stove when burning at higher temperatures have more heat go up the chimney?


 
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Post by Rob R. » Wed. Jan. 25, 2023 10:52 am

Yes. Hence my comment about difficulty of setbacks with hand fired equipment. The energy saved during the setback period has to be greater than the energy wasted by pushing the stove out of the sweet spot to recover the temperature. The longer the setback period the better the math works out.

With that said, I did not notice this was in the hand fed section of the forum. If you are discussing the merits of using setbacks only with hand fired equipment, that changes things a bit. Most of the hand-fired crew will never consider a setback anyway, so I will stop debating it. Whatever works good in your house is fine with me.
I use 1.5 ton of coal a year...and using the calculator it says I will need so many gallons of fuel oil...and I'm way, way, WAY above that. Regardless of the reason why it doesn't compute.

I can show you bills (cost and fuel use) to keep my home 68 degrees, let alone 70 (coal is higher house temp at 72-74 where ever I decide & 1.5 ton/yr usage), versus my coal usage at a constant...and remember the fuel oil is intermittent.
I believe you. What you have described is very common when people compare oil consumption for central heat to coal consumption for a single stove. Reasons for this include:

The oil boiler/furnace is oversized and cycles a lot, and/or it is out of tune.
The oil boiler/furnace heats the basement and the coal stove does not.
The oil boiler/furnace keeps the average temperature of the entire house warmer than the coal stove.

I have swapped multiple homes over from heating with an oil boiler to a coal boiler, and in those cases the math has worked out very close to the fuel calculator.

 
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Post by ColdHouse » Wed. Jan. 25, 2023 12:09 pm

Rob R. wrote:
Wed. Jan. 25, 2023 10:52 am
Yes. Hence my comment about difficulty of setbacks with hand fired equipment. The energy saved during the setback period has to be greater than the energy wasted by pushing the stove out of the sweet spot to recover the temperature. The longer the setback period the better the math works out.

With that said, I did not notice this was in the hand fed section of the forum. If you are discussing the merits of using setbacks only with hand fired equipment, that changes things a bit. Most of the hand-fired crew will never consider a setback anyway, so I will stop debating it. Whatever works good in your house is fine with me.



I believe you. What you have described is very common when people compare oil consumption for central heat to coal consumption for a single stove. Reasons for this include:

The oil boiler/furnace is oversized and cycles a lot, and/or it is out of tune.
The oil boiler/furnace heats the basement and the coal stove does not.
The oil boiler/furnace keeps the average temperature of the entire house warmer than the coal stove.

I have swapped multiple homes over from heating with an oil boiler to a coal boiler, and in those cases the math has worked out very close to the fuel calculator.
I am considering your information educational so please do continue.

Considering I have 2 hand fired stoves, am I off base to have reached the conclusion that trying to heat to my present 70* comfort zone in an arctic freeze would render wasted energy up the chimney?

 
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Post by Retro_Origin » Wed. Jan. 25, 2023 12:32 pm

If anyone other than Rob had mentioned about the setbacks I might have disagreed, but I've come to see his opinion is usually backed by quickly proven facts. I think this is an easy illustration everyone can understand: If you turned your thermostats back to 50 and left the house for 5 days, then turned it back up to your typical setting, would you have saved fuel. Obviously yes, the question is rebound time in reference to setback temp. Maybe what opposing arguments are saying without realizing it is that it takes longer to rebound after a setback and then associating that with more fuel consumption. I stopped doing setbacks because it was cold and annoying to wake up to

 
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Post by Lightning » Wed. Jan. 25, 2023 12:47 pm

The drop to set back and the ramp up to get back to normal wash each other out. The savings happens in-between those two points.

 
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Post by Hoytman » Wed. Jan. 25, 2023 12:49 pm

I could do the same with a coal stove, or wood stove and dial the stove back once the furnace wall thermostat is at target temperature.

50 degree house, fire the stove up then I cut the stoves back to maintain the house temp once I reach target temperature.

One could likely calculate the rate of fuel to maintain that target temperature.

The difference is the house isn’t yet saturated with heat…and I’ll likely need to turn it down even further because in about 12-36 hours the house and everything in it will stabilize and I’ll be burning less than when I first turned the stove down at the target room temperature.

With radiant heat the envelope warms up. My IR gun confirms this…while the air temperature is at target.

With my furnace air temperature remains at target (close enough) but my IR gun shows colder walls and floor temperatures.

So once the envelope is saturated I burn the stove even lower than what it was first turned down to. You play with it until it all equalizes over a few days.

I believe any potential air leaks come through a warm envelope slightly warmer than with the furnace running so less of a draft is felt. A perception that is very real. The house feels more warm because it is. Objects equalize with the air.
Last edited by Hoytman on Wed. Jan. 25, 2023 1:48 pm, edited 2 times in total.

 
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Post by ColdHouse » Wed. Jan. 25, 2023 12:58 pm

Retro_Origin wrote:
Wed. Jan. 25, 2023 12:32 pm
If anyone other than Rob had mentioned about the setbacks I might have disagreed, but I've come to see his opinion is usually backed by quickly proven facts. I think this is an easy illustration everyone can understand: If you turned your thermostats back to 50 and left the house for 5 days, then turned it back up to your typical setting, would you have saved fuel. Obviously yes, the question is rebound time in reference to setback temp. Maybe what opposing arguments are saying without realizing it is that it takes longer to rebound after a setback and then associating that with more fuel consumption. I stopped doing setbacks because it was cold and annoying to wake up to
No. I am questioning if a coal stove running to capacity has more heat going up the chimney than one that is simmering on low.
I think I stated that I had my oil boiler on a timer and believed it saved fuel. I don't know how much it saved because I never heated the mass and kept it warm and compared that to heating short periods of time. Furthermore, there is a big difference between closing down a house for a week or extended period of time and shutting it down for 2/3 of each day.

 
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Post by ColdHouse » Wed. Jan. 25, 2023 1:01 pm

Lightning wrote:
Wed. Jan. 25, 2023 12:47 pm
The drop to set back and the ramp up to get back to normal wash each other out. The savings happens in-between those two points.
Would that be true if the ramp up equated to higher exhaust temperatures exiting the chimney?

 
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Post by nut » Wed. Jan. 25, 2023 1:31 pm

Lightning wrote:
Wed. Jan. 25, 2023 12:47 pm
The drop to set back and the ramp up to get back to normal wash each other out. The savings happens in-between those two points.
Does that mean short setback periods don't save energy?


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