Heat Pumps

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Bob F wrote:

Well, assuming one doesn't account for the energy inputs into producing and transporting the gas which I'm quite sure aren't in the thought process here.
Of course, thermal efficiency of central generation runs in the 30-40% range whereas (modern) gas furnaces are 80% or higher so superficially one knows where it's coming from.
But, of course, what's significant to the homeowner is what is the cheaper alternative which can be the heat pump in many areas; particularly if were geothermal instead of air-exchange.
But, as you say, only comparatively small amounts of the overall electric grid are gas. I was looking at some data the other day and iirc w/o looking it up again, it's about 9% nation-wide, about half of nuclear. Much of that is peaking capacity although there are baseload plants in areas that do have local large supplies or in some areas where it was all that could be permitted when utilities had no choice but needed more capacity.
It is, of course, a really silly way to use up natural gas supplies...
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Of course it obviously isn't so, and it's not the energy to transport it that's the big piece missing. A heat pump is not resistance heat. For every KWH you put in, you get much more out than if it were a resistor. 3X is typical. That's why the heat pump can be more cost efficient.
Also, most electricity is not generated from gas, but cheaper fuels like coal.

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snipped-for-privacy@optonline.net wrote: ...

Like, DOH!!!???
The point I was making is that a gas furnace isn't 80% (or whatever) efficient, either, when one includes the energy required to produce and distribute it, just as it doesn't make sense to talk about the efficiency of the power plant for electric heat--

You mean like ...

maybe???
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That would be true if you were talking about generating heat using resistance heating. A heat pump is just that, a pump. It moves the heat, as opposed to generating it. Which is why in most cases they are cheaper to heat with than gas, down to a certain temp. In most cases that temp is going to be at least in the 30s.
We had a heated discussion about this in another thread. If you run the numbers, it's cheaper to use a heat pump here in NJ or probably much of the northeast, down to about 32F. We have electricity costs over 15 cents/KWH. If you live somewhere with cheap electricity or expensive gas, the temp can be much lower. Bubba showed that with 8 cent electricity and an efficient pump, the heat pump is cheaper down to even 10F.
How appropriate a heat pump is then depends on how much of the heating season you would be below that economic transition point. Even if you're below it some of the time, overall the heat pump could be more cost effective to run. And a dual fuel, gas/heat pump would be even better.
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On Feb 19, 6:04 pm, snipped-for-privacy@optonline.net wrote:

Please remind me of this again the next time I have to right out a check for almost $700 to power that damn heat pump.
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On Thu, 19 Feb 2009 18:18:24 -0800 (PST), BobR

Your unit isn't functioning correctly. I live in Central mo, and even with a very inefficient model, we never had bills like that.
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I have had it checked by two different companies and both said it was functioning just fine for whatever that is worth. Look at it this way, how effective is an air conditioner going to be at keeping a 70 degree temperature when the outside air temp is over 120 degrees? That is the same thing you are trying to do by keeping a house at 70 degrees when the outside temperature is 20 degrees. A heat pump works on the difference in the temperatures and beyond a 30 degree difference, it isn't efficient.
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On Fri, 20 Feb 2009 15:30:29 -0800 (PST), BobR

HeHeHe. You are such an Einstein BobR. Im speechless. Bubba
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My heat pump is an air transfer type. It is a very efficient air conditioner. It doesn't put out enough heat to keep the house warm in the winter if the temps drop below 35. I have a pellet stove that I use a lot in the winter but when I have trouble with it, the heat pump just doesn't help much.
But I live in Michigan. I don't know how bas your winters are in Dallas. If your area doesn't have freezing temps for weeks at a time, you might be happy with an Air Transfer heat pump instead of the more expensive (but better) Geothermal type.
David
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I live in the Dallas area and unfortunately have an air transfer heat (joke) pump. I can assure you that I am NOT happy with it and would never recommend that anyone use one. They might be better that resistance heating in the moderate temperature range but when the temps drop below about 35 degrees they will eat your lunch on cost to run. The colder it gets, the more they run and the less they heat. When the temp drops below about 20-25 degrees, they are lucky to maintain 65 degrees in the house. My thermostat was set at 67 degrees and there were nights when the head pump ran the entire night and couldn't hold the 67 degrees. Result was a $670 electric bill for the month to heat a 2200 sq.ft. house.
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On Thu, 19 Feb 2009 15:48:48 -0800 (PST), BobR

Bob, It sounds like you have a heat pump that was either not sized properly or the attached ductwork wasnt or both. Granted, the temp coming from a heat pump registe is NOT the temp of an oil or gas furnace but they do heat homes reasonably well. When confronted with high fossil fuel cost they are a really good alternative. Thats why the dual-fuel/hybrid systems are gaining such popularity. It helps control your utility bill. In my particular area, gas is high, electricity is low so heat pumps are typical. You should have someone competent look your system over including doing a heat loss/heat gain on your home and checking your duct system for proper sizing (manual D). Armed with that, you will then have a better understanding of what you have and what you need. By the way, that service doesnt come free. Then, with that ironed out and a properly set balance point (which as trader said could be in the 30's or down into the single digits) you will have an efficient comfortable system in your home. Bubba
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It actually is a larger system than what should be needed for a house this size.

They might work great in areas where the temperature never gets below 40 degrees but below that they lose efficiency so fast that they become almost worthless. Below 20 degrees they can no longer extract enough heat from the outside are to hold an interior temperature.

Most electricty plants use some form of fossil fuel and the conversion to electricty followed by conversion to heat is very inefficient. Direct conversion is always preferrable and less costly.

I have had this done, thank you and it was far from free. The system is only 5 years old and has been maintained twice annually. The fact is that it just sucks when the temperature drops.

Damn don't I wish. Better yet, I wish this damn neighborhood had available gas service so I could get a good system.
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On Thu, 19 Feb 2009 18:10:34 -0800 (PST), BobR

Exactly as I seem to have stated. Why would you make it too big or too small. A proper load calculation would tell you EXACTLY what size you need. Nevermind. No response is needed. I see the start of a long thread.

Im glad to see you have been following along so well for the last month. I guess we all have our own opinions of what a heat pump is capable of. :-)

?? Direct conversion?? But most of us stopped burning coal for heat maybe 50 yrs ago. Nevermind. That one also needs no response.

I didnt say it was free but it doesnt appear that you had a CORRECT load calculation done. If you had, you wouldnt have installed a larger unit. Too bad.

but if you spend $600 or more to heat with a heat pump, what do you think your gas bill would be? Im not sure but I dont think natural gas is cheap in too many places. Bubba
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I had gas heat and went to a heat pump with NG backup heat. I think the cost to heat my home this winter compared to last winter is nearly half Gas heat kicks in when its 38F outside.
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I'd be curious to here all the facts from BobR's case in Dallas. We only have one small part of the picture here, What we don't know:
Backup heat source? gas? electric resistance? Cost of electriciy Cost of gas? What size house is running that $700 bill, which I assume is for the coldest month? If it's that inefficient, have you replaced it with something else and what are the bills then?
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On Feb 20, 8:51 am, snipped-for-privacy@optonline.net wrote:

The backup is electric resistance and doesn't seem to be able to overcome the cold when it goes below about 35 degrees. Cost of electricty is 14.5 kwh if I recall correctly. Since I don't have gas available now, don't know the cost but do know that the electric rates are based on gas cost. The house is about 2300 sq ft and the $700 was for December-January (10-10th). The cost was similar last year for most of winter.
Bought this house three years ago. Prior house had 3500 sq.ft. with gas heat and the highest electric bill ever was about $270 (Summer of 97) with highest gas bill of $95. Normal electric bill for winter months was $120 with gas running $80. Summer saw the gas drop to $25 with electric around $225.
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I think a system like that might just work pretty well but a heat pump that must fallback on all electric below 38F is not going to save any money and will probably drive your bills up considerably.
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On Fri, 20 Feb 2009 15:42:10 -0800 (PST), BobR

Geez, I wonder what all those millions of people out there with systems exactly like that are going to do? Bubba
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Continue to pay through their ass just like I am until they can afford to replace the entire piece of crap. In the mean time, I will continue to let them know that heat pumps are NOT all that some people try to make them seem. I have several neighbors who would concur with that as well.
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On Fri, 20 Feb 2009 18:41:52 -0800 (PST), BobR

BobR, You need to understand. If you have a heat pump with electric heat back up, your heat pump will continue to produce more heat for the dollar than straight electric heat. You will find the exact point by looking at a performance chart of your unit. Yes, as it gets colder out, it will seem like the damn thing runs forever and the air coming out is cold but if properly installed it WILL provide heat cheaper than your resistance electric heat until the COP's get to a 1:1 ratio. Now if your heat pump is teamed up with natural gas, propane or oil, then you will have to use one of the calculators to get an idea at what point you want to shut the heat pump off using the economic balance point and thermal balance point calculations. If you had been following along these past weeks you would have caught on to a little bit of this over the rhetoric being exchanged. Bubba
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