heat pump -elect coils

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My daughter is complaining about high heat bills. i bet the elect resistence elect coil is on a lot. how do i tell when the coil comes on? and how do you turn it off? what turns it on? when temp is below 32? if compressor is ok, why would coil come on? she had the system checked and they said ok. wonder if they checked out operation of coils. thanks for any insight. bill in Maryland
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One big thing to watch for with a heat pump is turning it up and down. Does she change the temperature or just sets it at one place and leaves it there. Most of the time the heat strips will come on if you go up about 3 or 4 degrees at one time.
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Yes! That is a major drawback in some circumstances. I used to have all-electric. The thermostat fortunately did have a light to indicate when the electric backup was on. I'd turn the heat down quite a ways when I was gone. Upon return, I'd turn it up just a few degrees at a time, keeping the electric backup from coming on. I eventually got around that by putting a toggle switch on the thermostat. The backup would only come on when I wanted to let it; I could set the heat to warm up however far I wanted without worrying about the electric backup.
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The electric heaters come on when the room temperature (at the thermostat) falls more than a few degrees below the set point. They also come on when the heat pump (outside unit) goes into defrost.
In some installation, the thermostat has a lamp that comes on when the resistance heating is being called for.
My system came with a total of 60 amps (about 15kw) of available resistance heating. In my case, it was easly to arrange things so that only 20 amps of resistance heating would be switched on. Obviously, when it gets VERY cold outside, the inside temperature sags! It's a question of money vr. comfort.
We compromise with a combination of LPG ventless heaters and small electric heaters that give some extra heat where the people are.
The quick and dirty way to save money is to turn the thermostat down to, say, 60 or 65 and use small electric heaters (750 watts) where you want the extra heat like when you are watching TV. Waterbed heaters and electric blankets also make it possible to be comfortable when the house as a whole is on the chilly side.
I agree with the other poster who said that you should pick a thermostat setting and leave it alone. Timers cause more problems than they solve when you have a heat pump.
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This is a very timely conversation for me. I just replaced my aging heat pump with one of the top of the line Carrier units. The literature estimated I could save as much as 60% over the 10 year old unit. (BS of course) Last months electric bill just came in and I used more electricity than the same period last year. Temps have not been unusual this year. This unit came with a set back thermostat and I drop the temps overnight about 8 degrees. As you can imagine the heat strips kick in when it tries to bring the temps back up to daytime levels. I was wondering if I was wasting more power than I was saving by running the unit this way. Is there any temp setback that might give you some savings or is it really best to leave it fixed?
Rich B www.beachtradingco.com
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I didn't install any resistance heating, just a clock that runs when the system wants to turn it on. I light the wood stove instead :0
Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/
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Face it, heat pumps are the most ignorant system ever developed and suffer from a basic design fault. The lower the temperature, the less efficient they become and nothing will help the electric bill from skyrocketing. Heat pumps are ONLY effective in the few southern states where the temperature does NOT go below 40 degrees for any extended length of time. Below 32 degrees, they are a total joke.
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On Thu, 31 Jan 2008 08:05:30 -0800 (PST), BobR

With all due respect, Bob, a properly sized heat pump can continue to provide economical heat at temperatures well below 0C or 32F.
The Nova Scotia Department of Energy has a chart that compares the operating costs of various heating systems and an air source heat pump with a HSPF of 6.5 (COP of 1.9) is shown to be less expensive than electric heat, oil, propane and wood pellet, and competitive with that of a mid-efficiency natural gas furnace.
See: http://www.conservens.ca/consumerinfo/residential/reducingenergybills/existinghomes/spaceheatingcostcomparisons
For an older home with a heat demand of 80 MMBTUs per year, the cost of electric baseboard heat is said to be $2,851.10; that same home equipped with new oil-fired boiler operating at 83% AFUE is $2,559.71 and a condensing propane unit with an AFUE of 93% will set you back a whopping $3,372.12. By comparison, the annual operating costs of an air source heat pump are $1,500.58.
Note that the numbers for oil and propane heat are based on fuel cost of $0.85 per litre and, at this time, oil and propane are running at $0.95 and $1.05 a litre respectively, so the relative performance of an air source heat pump is even better than what's shown here. Note too that our winters are comparable those of Minnesota (e.g., Minneapolis-St. Paul at 7,882 HDD, versus Halifax, N.S. at 7,861 and Truro, N.S. at 8,132 HDD), so this isn't exactly what you'd call a "southern" climate. Finally, a mid range heat pump with a HSPF of 8.5 would be 30 per cent more energy efficient than the one used in this example.
Cheers, Paul
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On Thu, 31 Jan 2008 08:05:30 -0800 (PST), BobR

Nice to know you are so fuquering stupid BobR. Get a clue and a brain and come back when you actually know something useful. Heat pumps work very well. Mine heats my home until about 17-18 degrees outside. Then it starts losing temperature so the back-up heat kicks in. I'll sell you a home with straight electric heat and I'll take the same EXACT home except I get a heat pump. We'll compare bills each month. You'll be hurting. Bubba
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Comparing the Heatless Pump to pure electric heat might be a valid point but comparing to Natural Gas or even propane is a damn joke. Yes, mine also heats down to 17-18 degrees but in order to do so it must run almost continously and the electric bill for winter heating is double my bill for cooling in July and I live in DALLAS where it doesn't really get all that cold but it does get that hot. I have had it checked, checked, and checked again and even the Air Conditioning people admit that they are worthless pieces of crap.
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On Thu, 31 Jan 2008 12:43:35 -0800 (PST), BobR

Yes, around 20 or so outside it seems to run 24/7 or something like that, HOWEVER........................ The next time it is that cold out, go out and wrap and amperage meter clamp around the run or common terminal of the compressor and not the amperage draw. Now, wait till it is 95 outside or some sweat busting temperature like that and measure that same wire with your amp meter. BIG difference. Heat pumps work if installed correctly paying careful attention to equipment sizing and duct sizing. No, its not as warm as gas, oil or propane but saves tremendously for those that only have the option of electric. Bubba
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A heat pump using ground heat and cooling would probably be as effective as anything available, gas or otherwise. The problem with the heat pump and most air conditioners is the reliance on ambient air temperatures which are totally ineffective at the time they need to be the most effective. The colder it gets, the more you need the heat and the less it is available. Likewise, when its super hot outside, you can't get any cooling out of the hot air. The only really effective method would be to bury the evaporator coils deep in the ground where the ambient temperature will remain almost constant.
That system is now gaining acceptance in many areas and is proving both effective and cheaper. Unfortunately, nobody in my area knows crap about it and even if they did, the soil around here is so unstable that it may prove ineffective.
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Bill,
Feel free to offer this factual information about air-to-air heat pumps to your bloggers.
1) Heat pump installations work best in locations where the heating load in winter nearly matches the cooling load in summer. This is usually not the case.
2) Heat pumps work best when maintaining a constant set point (i.e. no drastic set point changes or night setback).
3) A heat pump cannot supply all the heat a building will need except in warmer climates without supplementary resistance heat. A heat pump is basically a cooling unit and is typically sized for that purpose. Over sizing the unit to gain heating capacity will result in poor summer operation. The oversized unit will short cycle, causing inadequate humidity control.
4) It is essential that the defrost cycle be working properly or airflow will be restricted through the outside coil at below freezing temperatures lowering heat transfer and efficiency.
5) The resistance heat is in use during the defrost cycle.
6) Heat pump efficiency is mathematically greater than electrical resistance heat when it's warm outside. Coefficient of Performance for heat pumps are rated at 47 degrees F.
7) A heat pumps capacity, hence its efficiency drops as outside air temperature drops. Efficiency drops rapidly below 32 degrees F.
8) Heat loss from a building goes up as outside temperature drops.
9) The key to greater heat pump performance is capacity selection (sizing). See 1 and 3 above.
10) The most energy efficient heating or cooling system is the one that's not operating. Insulate and lower the set point.
On Thu, 31 Jan 2008 18:09:02 -0800 (PST), BobR

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Thanks for answering my piece of the question. I called the company that installed my heat pump yesterday and they recommended that I not set back more than 5 degrees. The aux heat strips automatically kick in if the temps need to be raised more than 3 degrees and more strips run the longer the unit is working to raise the temps. Based on that I've set the overnight temps to drop 2 degrees and I'll see how that works. I'm in SC and Feb is typically the highest wintertime usage so it will be interesting to see the impact of having a more constant temp.
Rich B www.beachtradingco.com
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You may have a couple of options of what delta it kicks in at depending on the thermostat. Set via digital or by jumpers inside. Check the instruction sheet.
Another option is if you have an extra program available you could bring it up 3 degrees at a certain time then an hour later bring it up another few.
Not sure if you realize that once the delta is within the setting the strips should kick off and pump continue to run until temp is reached (plus maybe 1 degree).
Red...
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Thanks for that Red. I'll try your suggestion of stepping it up. That sounds like a great idea.
Rich B www.beachtradingco.com
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Note that there are some programmable thermostats that "understand" heat pumps. There are some that are smart enough to bring the temperature back up from the set back in increments of a few degrees at a time, so the HP never thinks it's gotten too far behind. There are others that "know" that the abrupt temperature discrepency (between room temperature and setpoint) is due to their "returning from setback", inhibit backup heat, and force the HP do do all the work. The latter have to be built into the HP I believe.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
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Thanks for that Chris. This unit has the Carrier Infinity Control thermostat. This thermostat know's what components are attached to it and it monitors and controls the system. Their implementation apparently thinks it's more efficient to have the backup heat kick in if the temp needs to be raise beyond a certain number of degrees. I'm told that's 3 degrees. I've decided to only drop the temps overnight a couple degrees and see what the impact is on my electric bill next month. Of course as soon as I did that the temps rose to the 60's and 70's so the HP won't run anyway. ;-)
Rich B www.beachtradingco.com
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What happens is this: most HPs think that a discrepancy of over N degrees (somewhere around 5) means that the HP is unable to keep up, and backup heat is essential to get the heat back to where you want it ASAP. It's not more efficient, it's _quicker_, a simpler programming choice, safer choice (more likely right without more complicated analysis/sensors), and more in keeping with what the designers think _you_ want ("I'm freezing, MORE HEAT NOW (*&&^)(*&!").
It sounds as if you're doing your setbacks manually. If that's the case, the Tstat isn't designed for that, and is going to make suboptimal choices - when you set the Tstat up, it thinks "my owner is cold, I'll warm him up ASAP!". If you want to continue doing that, make your temperature changes gradual. Or use a diferent thermostat.
On our HP/gas backup, we went with a programmable control unit that physically moved the control on the existing thermostat. There were no other options for controlling HPs at the time. I understood about backup issue, and since the unit permitted me to make as many as 20 or so programmed-time temperature changes, I simply set a single "setback" step, and a series of gradually rising "recovery" steps. Worked fine - our heating bills were ridiculously low (for the great white north that is). Just took a while to program.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
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On Tue, 05 Feb 2008 17:29:31 -0000, snipped-for-privacy@nortelnetworks.com (Chris Lewis) wrote:

Hi Chris,
A friend of mine installed a new setback thermostat for his heat pump (a Honeywell as I recall) that monitors how long it takes to return to the daytime set temperature and adjusts the timing of the ramp up period accordingly; in other words, the heat pump comes on earlier during colder weather so that the house reaches the desired temperature at the time requested. He tells me his backup elements never come on as they did previously with his previous thermostat and his operating costs have dropped accordingly.
I always chuckle whenever someone tells me heat pumps don't work in northern climates or when temperatures routinely fall below 40F. Compared to my oil-fired boiler at 82% AFUE, my heat pump has cut my overall heating costs by more than half -- an average cost of just 4.3 cents per kWh of heat versus 10.8 cents for oil.
Cheers, Paul
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