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
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.
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.
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.
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.
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?
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.
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.
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
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.
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.
Yes, around 20 or so outside it seems to run 24/7 or something like
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
Now, wait till it is 95 outside or some sweat busting temperature like
that and measure that same wire with your amp meter.
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.
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.
Feel free to offer this factual information about air-to-air heat
1) Heat pump installations work best in locations where the heating
winter nearly matches the cooling load in summer. This is usually not
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
warmer climates without supplementary resistance heat. A heat pump is
basically a cooling unit and is typically sized for that purpose. Over
the unit to gain heating capacity will result in poor summer
oversized unit will short cycle, causing inadequate humidity control.
4) It is essential that the defrost cycle be working properly or
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
heat when it's warm outside. Coefficient of Performance for heat pumps
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
See 1 and 3 above.
10) The most energy efficient heating or cooling system is the one
operating. Insulate and lower the set point.
On Thu, 31 Jan 2008 18:09:02 -0800 (PST), BobR
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
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
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
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).
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.
Age and Treachery will Triumph over Youth and Skill
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. ;-)
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
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.
Age and Treachery will Triumph over Youth and Skill
On Tue, 05 Feb 2008 17:29:31 -0000, firstname.lastname@example.org (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.
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