That's a bit on the low side -- about right for sleeping. 'resting' is more in the 110-120 range. Circa 125 is frequently used for estimating purposes.
Call it 12,000 BTU/hr per room, plus another few thousand for the lighting.
Scale up by a factor of 4, for equivalent footage to a medium house, and you've got the equivalent of an 80% efficient 150,000 BTU/hr furnace running at a _50%_ duty cycle.
Surprisingly small differences. lower elementary ages are about 75-80% of adult.
Depending on activity level, you can _triple_ (or somewhat more) the base number, which is in the 100-140 watt range.
A 250 watt kid is -not- all that extreme!
snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) wrote in news: snipped-for-privacy@corp.supernews.com:
Also, I think that heat dissipation would be equivalent to body surfacce area, which would make skinny kids radiate more (proportionally) than chunky ones ...
While you might think so, reality is somewhat counter-intuitive. :) Total heat output is relatively -independant- of surface area. Less skin just means more output per unit area.
You know, I know exactly what you are saying -- our son has been like that also.
Hi Chuck,
It would seem that I have not communicated clearly...
Indeed, the design folks tell me not to use any setback, but they seem unable to tell me "why." Their lack of a meaningful explanation was the cause of my original question about the setback issue.
All the best,
The rate at which your house loses heat to the environment depends in an almost linear fashion on the temperature difference between your house and the outside environment.
So as your house cools, the rate at which it loses heat will decrease. Keeping the house at the higher temperature means it will constantly lose heat at that higher rate, and all of that heat lost must be mad eup to maintain the temperature. If you let it cool down and heat it back up the 'stored' heat that is lost to the environment while cooling is exactly equal to the extra heat needed to heat it back up. But the heat loss to the enviornment is less the whol time during which the house is cooler than normal.
Ergo, it ALWAY will use less heat to let it cool down and heat it back up than to maintain it at the higher temperature.
What comes into play is the cost of pumping that heat into your house at the higher rate for the short period of time during which it heats back up. If that is down with auxillary electric resistance heat that MAY cost more or use more energy overall than just keeping it warm.
The presumption that you have an auxiliary heating system may be part of the reason why you get advice to the contrary. Another concern may be that cycling the temperature may result in persistent cold spots or condensation problems that could lead to overall dissatisfaction with the system.
But mostly I doubt you have ever spoken on the phone with anyone who actually studied heat transfer phenomenon or even took a physics course ever.
The other possibility suggested is that extracting heat too fast from the groundwater could create a pool of cooled water underground with a resultant lower efficiency of heat extraction. That would depend largely on the groundwater environment and how extensive the heat exchange area is underground.
I doubt that a definitive general answer can be given regarding that last concern. It would be highly dependent on the specific situation.
No, the reason is that it costs them money to keep it warm and it also costs them money to warm it up , but they can produce a product while it is warm and not while it is warming up.
It is not how much they are spending on energy, it is their return on that investment--less than zero (due to other operating costs) while warming up, and greater than zero (hopefully) when at operating temperature.
There are other considerations such as thermal stresses during warm-up and cooling down.
That is the first I ever heard of that.
The higher the flow rate the higher the Reynolds number and therefor the higher the convective heat-transfer coefficient. You may get less heat transferred per gram of water flowing through the radiator, but not in inverse proportion to the rate at which grams of water flow through. IOW you might get only 75% of the heat loss per gram of water but will have twice as many grams of water flowing through.
Yes, it's simply wrong in general. If one didn't get additional cooling capacity when the thermostat opened as compared to when it is closed, there would be insufficient cooling capacity to prevent overheating at almost any operating condition.
Whatever "caveats" were suggested to counteract that would have to be extreme, indeed...
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If he's talking bout a new engine them maybe removing the radiator could confuse the computer and really screw things up--but since normal operation is for the thermostat to open when the water gets hot--how COULD it overheat by leaving ti open? Once it gets hot, it would open anyways.
Sound's like an old wive's) mechanic's tale.
Er, I meant removing the 'thermostat'.
There is little doubt that removing the radiator will cause the engine to overheat...
Hello to all (again),
Well, I am the OP on this "Will I save if I use a thermostat setback on my geothermal system" thread, and I believe that I now have an answer:
Part of the hassle I faced in experimenting with this was that for some reason, I kept thinking only of my house. We have a number of electrical appliances there that are used (essentially) randomly, and their use would certainly throw off any comparisons that I could make over a relatively short period of time.
I commented on that to my wife, and she said "So do the experiment in the barn." (She did not actually say "So do the experiment in the barn, you idiot", but that is what I heard.)
Our office-barn is heated with exactly the same system as is our house (water to air geo with no backup resistance heat) and there is no variability of electrical consumption other than the heating system for most of each day.
So, with that information, I did a very simple experiment. I have run it only for six days but, as you will see, the pattern seems quite clear:
I set the programmable thermostat to drop the "call heat" temperature by 10 degrees F for 12 hours on alternating nights.
Each morning, at the same time, I read the barn's electric meter.
Finally, I got the degree days, and wind speed, from a weather service site.
With that, I could calculate the ratio of KWH to Degree Day. I have also included in the table below the reported max wind speed for the day.
KWH/DD WS
Day 1: 1.2 (setback) 14
Day 2: 1.6 (no setback) 17
Day 3: 1.0 (setback) 8
Day 4: 1.3 (no setback) 0
Day 5: 1.0 (setback) 12
Day 6: 1.2 (no setback) 3
So, on the days with setback, the mean KWH/DD was 1.06. On the days with no setback, that mean was 1.36.
The resulting savings are approximately 22%.
I do remain baffled by the reasons the geothermal folks (installers, designers, sellers) seem to be consistent in suggesting that such setbacks are not of value.
All the best,
Kenneth wrote: ...
As at least one other poster noted, they're concerned w/ other factors that aren't applicable in your case (primarily dominated by the use of resistance electric heat in many/most systems)...
There are others including the potential freezeup, etc., that are possible but imo they're mostly cya kinds of responses. Did you try the Water Furnace people directly or contact the Okla State or some of the other resources for other input?
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Howdy,
The CYA analysis makes sense to me, but as you probably know, there is no real "freeze up" danger at all. These systems simply turn themselves off is the incoming water is too cold.
Also, as you may know "Water Furnace" is a brand name. Our equipment is ClimateMaster.
I have communicated about all this at some length with the ClimateMaster folks, with the geo folks from my electric utility, and with the installer of the equipment. They all have said "no setback" is best.
All the best,
The problem I've normally seen is on the once-through water exchange systems (which is also what I think I recall being mentioned in one of the earlier postings of a problem--whether it was yours or another I don't recall) is the freezeup of the outlet when systems aren't running. My opinion remains as I noted there is that if that's a problem for a given system, it will be so whether there's a setback or not unless the system is so undersized as to run continuously; hence my assessment of that as a response as being in the "CYA" category.
Yes, I had thought that was who you had said earlier...I don't know ClimateMaster; had a Water Furnace system earlier and was pretty impressed w/ their factory rep service/technical support.
I think again all of those folks are addressing the general case still rather than the specifics of a given installation and are still using the answer that is easiest for them. It would be interesting if could get to one of the actual research facilities that might address a specific system rather than the general consumer response. If you were still interested in pursuing it from that standpoint I'd again suggest ORNL, TVA R&D (not power) or OSU might be more likely to answer a real question.
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Hi again,
For me there are two (essentially unrelated) issues:
First, I am concerned with my system(s) and whatever savings I might realize with the setbacks.
Second, I am a curious sort, and often enjoy understanding this sort of thing.
Right now, my energies are focused on #1, and with my very simple experiment, I do believe I have my answer.
#2 will have to wait a bit!
All the best,
Kenneth wrote: ...
The answer to the first is clear -- a lower setpoint is less total integrated demand as compared to no setback so unless there are mitigating factors such as the higher-rate aux heat (that you don't have), then a setback will invariably be less input.
The other issues are also system-specific but the design issues have been dealt with by the various research groups. I never had a convenient water source so didn't pursue the logistics of them that much.
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What was the recovery time after the setback days?
I'm wondering if your savings aren't as great as you think. The reason is that on a setback day, you have zero electrical usage as the house coasts down to the setback temp. The next day's usage gets nailed with the recovery time usage. Perhaps week long vs day long alternating periods might mitigate some of this effect?
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