Thermostat settings

[tedkidd]

More great stuff:

Go big to go low: Maximize the efficiency of your heat pumps, chillers, boilers and solar systems by getting the return temperatures down in heating and up in cooling

low and slow, can't do that putting the pedal to the floor...

Firing a high efficiency boiler to high temperatures with a programmable thermostats does not change the fact that the boiler is behaving like a mid efficient appliance.

ditto...

The skills of an indoor climate engineer in designing a system for effectiveness and energy efficiency should never be confused with picking HVAC equipment out of catalogue nor the contracting skills it takes to assemble components on site.

Message: To obtain the rated performance from a high efficiency boiler you have to operate it at a low return temperature which can be achieved with a weather compensator and a heating system that has been designed for low temperatures.

Adding programmable setback thermostats can provide some additional conservation measures in some systems but more so in low mass air based or baseboard systems and less so in radiant floors, walls or ceilings.

Make note that when programmable stats are not properly used due to their complexity they can actually increase energy consumption rather than reduce it and finally, if moisture is not controlled in the space, setting back the space temperature can cause condensation on cooler surfaces.

http://www.healthyheating.com/Window...mperatures.htm

SO UNLESS YOU ARE GOING TO TEST AND MEASURE AS BT HAS, DON'T SIMPLY ASSUME SETBACK SAVES.

[54regcab]

Re. underfiring - I've had to re-think my position on that. I took Jim Davis's combustion analyzer class last week and he raised the matter or what happens to heat transfer and efficiency when the flame is lowered. I was especially interested since I have a two-stage furnace.
Jim's point was this - when the flame is lowered the gases at that point are farther from the heat exchanger walls and that lowers the efficiency of what should be the hottest part of the furnace. I recalled that every time I check the efficiency of a two-stage condensing furnace, the low-fire efficiency is below 90%. High-fire is up where I expect it to be, in the mid to high 90s. I'm considering raising the firing rate of low-fire as high as I can get it to maintain the efficiency rate of the furnace.
What do you guys think?

Have you measured the temperature of the flue gasses on high and low?

[kdean1]

I won't have time to check things until next week. I'll try to remember to take reading before as well as after.

[LKJoel]

For anyone claiming setback saves, I ask how much? 2 cents a day? 20?

Please prove it. I'm dying for someone to prove it. Prove it on a decent house with decent equipment, not a crappy house with crappy equipment and 4 windows open. I don't believe the savings, IF THEY EXIST, are MEASURABLE much less MEANINGFUL.

Look, you guys are some of the thought leaders. Please take a step back and question this bad dogma.

If you don't measure both ways you are guessing. Every house and the equipment therein are so different, that to know whether setback saves, does nothing, or even COSTS MORE is an unknown unless you actually test.

I believe setback is a complete myth, "world is flat" dogma blindly fed to us and followed without thought. So deeply engrained, even after rejecting it I have trouble fully shedding myself of the inclination to fiddle with my stat.

I believe Setback Dogma actually has many serious hidden costs, including being responsible for the problem of grossly oversized equipment (anybody think there is no energy cost there?).

Here's a paper I wrote:

http://bit.ly/energyvanguardsetbacksucks

The premise is free energy savings at no cost? Bullcrap. The interior temperature has to be much higher if you allow surfaces to go cold. Mean Radiant is critical to comfort: http://bit.ly/comfortcalculator

No cost? Bullcrap, rot and mold aren't free:


http://bit.ly/HHhpOverview

I'm seeing people abandon setback and save money. We need to be the thought leaders on fixing this 20th century approach to "saving", it needs to be removed from the current lexicon.

The earth is no longer flat, and that thinking is actually harming people and impediment to our industry's ability to do really good work.

While I agree on some level, I also see the benefits of longer off cycles and longer on cycles of equipment. I don't need my furnace to cycle on and off 5 times an hour to keep my house as close to 70 as possible. If I set it down to 65, it doesn't run all day (house likely wont ever even hit 65), then I get one good long run cycle out of it before I get home. Now you put this with a properly sized 2stg furnace, and you have a decent set-up. Not to mention cooling load, 2 good long run cycles in a day really help with the moisture removal, while a unit cycling to keep a house at 72 is removing mostly sensible heat. Watch your condensate off the Acoil, it won't start dropping until close to the 12 min mark, shorter than your average run cycle if your just keeping temp.

I do agree with you on principle though. Set-back saves little gas if any. There are, however, other benefits

[LKJoel]

Re. underfiring - I've had to re-think my position on that. I took Jim Davis's combustion analyzer class last week and he raised the matter or what happens to heat transfer and efficiency when the flame is lowered. I was especially interested since I have a two-stage furnace.
Jim's point was this - when the flame is lowered the gases at that point are farther from the heat exchanger walls and that lowers the efficiency of what should be the hottest part of the furnace. I recalled that every time I check the efficiency of a two-stage condensing furnace, the low-fire efficiency is below 90%. High-fire is up where I expect it to be, in the mid to high 90s. I'm considering raising the firing rate of low-fire as high as I can get it to maintain the efficiency rate of the furnace.
What do you guys think?

Very interesting. That may explain the trending I have been seeing of manufacturers moving away from a few big heat exchanger sections, and instead going with many small sections

[beenthere]

Re. underfiring - I've had to re-think my position on that. I took Jim Davis's combustion analyzer class last week and he raised the matter or what happens to heat transfer and efficiency when the flame is lowered. I was especially interested since I have a two-stage furnace.
Jim's point was this - when the flame is lowered the gases at that point are farther from the heat exchanger walls and that lowers the efficiency of what should be the hottest part of the furnace. I recalled that every time I check the efficiency of a two-stage condensing furnace, the low-fire efficiency is below 90%. High-fire is up where I expect it to be, in the mid to high 90s. I'm considering raising the firing rate of low-fire as high as I can get it to maintain the efficiency rate of the furnace.
What do you guys think?

Not worth it. You get slightly shorter run times. But that little shorter run time can also diminish some of the com fort you get from low fire. Its the long run time in first stage that provides the comfort that allows many people to set their thermostat lower, and save money on their heating bill.

[54regcab]

Slightly shorter run times and/or less cycles per hour with larger overshoots. Depends on how thermostat logic determines cycle time. Mine uses minimum on and off times. Some use degrees/cycles per hour but the oversized furnace heats the house up faster than the thermostat can register it. On my furnace (oversized single stage) I have it set at 5 minutes. 1 minute to start and preheat the exchanger, 4 minutes with blower, 3 minutes blower after burners shut off. House typically goes up 3 degrees per cycle, starts @ 68 and it's 71 by time the blower shuts off. 88,000btu in 1600sqft will do that, not sure what the builder was thinking. Never runs more than it's 5 minute cycle unless it's in recovery from setback.

[tedkidd]

Have you measured the temperature of the flue gasses on high and low?

Guess that might give some indication of which rate pulls more heat through the HE. That the thinking?

[54regcab]

Yes

[tedkidd]

NUTS, nothing more annoying than a link to a huge amount of reading. SORRY GUYS!!!! http://bit.ly/danholohan1992allshookup

Scroll down to the article All Shook Up.

Look for the heading "Low Water Temps" which explains the motivation for Europeans to chase getting more BTU from combustion.

Also look for other great stuff like "

Which only goes to prove that once you think you have it all figured out... you don't.

"

And:

From the beginning, the European heating engineers used wide temperature drops across their systems. Thirty-five to 40f is standard now. Her in the States, we typically work with 20f temperature drops. How come? Habit.

Is this guy GREAT or what!?