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'[OT] Heatpumps'
2004\10\11@041658 by Russell McMahon

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I just bought a second hand 2800 watt reverse cycle air-conditioner at a
(hopefully) good price with the intention of using it as a heat pump. It may
even last long enough to break even financially :-) (I estimate break even
to be 2 to 3 heating seasons).

Using it to pre-heating my hot water supply should reduce the breakeven
period to a year or so.

Has anyone here had any experience with hotwater preheating using a heat
pump? Any tips and tricks or traps?
The air-conditioner is a Fujitsu wall mounted unit with 2800 watts heating
capacity - quite small by most standards but should serve the house heating
task OK and would be nice if it could be easily adapted to hot water
heating.

Were it not for their cost, heatpumps seem the obvious answer to even
domestic heating needs. Being able to pay the power company 2/3 less seems
very attractive :-).

       Russell McMahon



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2004\10\11@104710 by Edward Gisske

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Russell,

You are getting into an area that has a put lot of dreams on the shoals...

At a minimum you will need to have an insulated pre-heat tank, a circulating
pump and an air-water heat exchanger. And, of course, a pic to control it
all.

It is important to remember that the 2800W is now going to be split between
heating your room and heating your water, so the room is not going to heat
as well as it would without the pre-heater topping cycle. The basic
home-heating furnace (in the northern US, where I live) is at least 50,000
BTU/Hr. The 2800W unit that you have is good for about 8500 BTU/hr, assuming
high efficiency. Hopefully, you live in a mild climate or have lots of warm
clothes.....

Heat pumps, in general, work better in applications where there isn't a big
difference between inside and outside temperature. I thought about using a
ground-water heat-pump system in my house when I built it but the economics
of it didn't make sense at the time (about 10 years ago). The other issue
here was that the government doesn't think highly of recirculating the
exchange water back into the well for fear of ground-water contamination.
Some people put a loop of heat-exchange plumbing down in the well casing to
avoid this problem.

Edward Gisske, P.E.
Gisske Engineering
608-523-1900
spam_OUTgisskeTakeThisOuTspamoffex.com

{Original Message removed}

2004\10\11@160818 by Morgan Olsson

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Edward Gisske 16:50 2004-10-11:
>Heat pumps, in general, work better in applications where there isn't a big
>difference between inside and outside temperature.

Amen.  I read a bout an industry that pumped heat from nearby river, into concrete floor, at 6x power factor.

Some more advanced pumps can cycle between warming radiator system at low temp (high efficiency), and hot water accumulator.

There mainly exist two good ways to lower temperature required: 1) Heat the floor, and implement it so that low temperature are needed (some thechniques require higth temperature)
2) Install radiators with (quiet) fans.  I have seen soe really quiet and efficient ones.


> I thought about using a
>ground-water heat-pump system in my house when I built it but the economics
>of it didn't make sense at the time (about 10 years ago).

My heat-pump is custom built to my preferences by a local firm.
I happened to have a very good well giving 9°C water, making for >3 times more heat energy out to my system than eletric power input.
Now the interesting custom part:
(This only use to be done on larger pumps)
The gas leaving the compressor is way over condensation temperature, thus by adding a small heat exchanger between the compressor exhaust and the condensation heat exchanger i can pull about 2kW @ 70°C while pulling 30kW @ 45°C main heat output.  (The high power is because is supplying two households)  The 45°C is for hous heating and first stage hot water, the 70°C is accumulated in a separate tank for final heating of hot water.
Thus, even when taking shower i have very high efficiency :)
(Values calculated by manufacturer, i can not measure but seem to corelate with experience from earlier weaker oil furnace) On the electric side there is consumed (measured) : Compressor 8,5kW, Ground water feeder pumnp 1,2kW, Intermediate media circulaiton pump (cold side) 370W, low temp local house 45W; remote 370W, hight temperature tank 40W.

I should have installed this long time ago instead of paying lot of money to pollute the world :/

:)

/Morgan
--
Morgan Olsson, Kivik, Sweden


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2004\10\11@170032 by Howard Winter

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Morgan,

On Mon, 11 Oct 2004 22:07:34 +0200, Morgan Olsson wrote:

> I should have installed this long time ago instead of
paying lot of money to pollute the world :/

Do you mind me asking how much a unit like this costs to
buy / install?

Cheers,


Howard Winter
St.Albans, England


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2004\10\11@192956 by Cnc002

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In a message dated 10/11/04 4:20:04 AM Eastern Daylight Time,
.....apptechKILLspamspam@spam@paradise.net.nz writes:

> Has anyone here had any experience with hotwater preheating using a heat
> pump? Any tips and tricks or traps?
> The air-conditioner is a Fujitsu wall mounted unit with 2800 watts heating
> capacity - quite small by most standards but should serve the house heating
> task OK and would be nice if it could be easily adapted to hot water
> heating.
>

I have a total electric home with a 4+ ton heat pump.  There is a hot water
recovery system installed, and it was installed by professionals, they don't
work.  During the summer it actually cools the water instead of heating it.  
Also, if you set the thermostats on the hot water heater to anything above 125
degrees F, the exchanger will cool it down no matter what the season.  I had the
HVAC company and the Electric co-op from whom I get my power out at least a
dozen times and we finally just shut off the valve to the thing.  My electric
bill actually went DOWN when I took it offline  The theory is that you can
actually end up getting your hot water free with the exchanger, it didn't work for
me, actually made my bill higher.

As for the heatpump, wouldn't want any other type of heating/cooling system.  
It is clean, very little maintenance and my electric bill runs me around
$150.00 to $180.00 per month. The people that live around me with homes similar to
mine pay around double that when you count their gas and electric bills.  
Plus, I have a drilled well so my water is also included in that monthly bill.

Randy Abernathy
4626 Old Stilesboro Road NW
Acworth, GA 30101-4066
Phone / Fax: 770-974-5295
Cell: 678-772-4113
E-mail: cnc002spamKILLspamaol.com
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2004\10\12@064319 by Russell McMahon

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> Do you mind me asking how much a unit like this costs to
> buy / install?

I'm mostly interested in this as a "how well does it really work in
practice" trial. At the price I bought it for it has the potential to save
$US500 pa after the first 2 months for as long as it lasts without
maintenance.

New heatpumps plus installation tend to cost so much that the breakeven is
often the better part of 10 years in a domestic environment. In my case the
unit cost me $US100 for a unit capable of 2800 watts of heating (a small
one) so the breakeven is much shorter - as long as it works and lasts a few
years. Used for hot water heating where the load is larger it would pay
itself back much quicker. This is  package unit so it doesn't need plumbing
into place - and has the disadvantage of therefore needing better placement.
IF you don't cost your (minimal) labour then installation cost is fitting it
into an exterior wall location and providing power. I happen to have a slot
that will take minimal work to fit it.

Savings per hour are

   KiloWatts_out x (COP-1)/COP x cost per kWh of electricity.

COP = coefficient of performance = watts_out/watts_in
For a heatpump COP > 1.
Most achieve about COP=3 although more is attainable and there are many
factors that affect this.

In my case cost of power = 12c/init (about $US0.08) (and it's increasing).
For COP = 3

Savings /hour = 2.8 x (3-1)/3 x $0.12 = $0.23/hour savings.
At a cost of $150 the breakeven = 150/.23 = 650 hours.
At 3 hours/day x 3 months per winter that's 650/3/30/3 = 2.4 heating
seasons.
That's pretty light heating. Spread it round and run it longer and it saves
quicker.

Used for hot water heating power use is probably say $3/day so savings are
$2/day so payback is in $150/$2 = 75 days ! :-)
Maybe that's a bit high. but you get the point.




       RM

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2004\10\12@071826 by Denny Esterline

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> Savings per hour are
>
>     KiloWatts_out x (COP-1)/COP x cost per kWh of electricity.
>
> COP = coefficient of performance = watts_out/watts_in
> For a heatpump COP > 1.
> Most achieve about COP=3 although more is attainable and there are many
> factors that affect this.
>
> In my case cost of power = 12c/init (about $US0.08) (and it's
increasing).
> For COP = 3
>
> Savings /hour = 2.8 x (3-1)/3 x $0.12 = $0.23/hour savings.
> At a cost of $150 the breakeven = 150/.23 = 650 hours.
> At 3 hours/day x 3 months per winter that's 650/3/30/3 = 2.4 heating
> seasons.
> That's pretty light heating. Spread it round and run it longer and it
saves
> quicker.
>
> Used for hot water heating power use is probably say $3/day so savings
are
> $2/day so payback is in $150/$2 = 75 days ! :-)
> Maybe that's a bit high. but you get the point.
>        RM

But these savings are based on a comparison between heatpumps and resistive
electric heat. The cost per btu for electric is 2.5 - 3 times higher than
the cost per btu of heating fuel. Even after factoring in the ~ %80
efficiency of most furnaces and water heaters, the break even is much
farther away. (of coarse the cost of fuel is rising, but then so is
electricity...)

-Denny



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2004\10\12@073110 by Russell McMahon

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> There is a hot water recovery system installed, and it was installed by
> professionals, they don't
> work.

Sombody has done something wrong somewhere, professional or not ! :-(
As the hot water is just a heat source and as the other heat sources for the
heat pump are liable to be colder than the waste water it just doesn't make
sense. Obviously the professionals agree :-)


       RM

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2004\10\12@074434 by Morgan Olsson

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Howard Winter 23:00 2004-10-11:
>Do you mind me asking how much a unit like this costs to
>buy / install?

The heat pump unit about 10.000 USD ex VAT
(Ready built freon R134something system complete with compressor*, control valve, simple electric cirquitry, pressostats, thermostat, three heat exchamgers)
* scroll type is more expensive than cylinder type, byt lasts longer.  IIRC expeted life is 20 years in my application.

Additional items:
o Intermediate water/alcohol system: Heat exchanger 600USD, pump 220USD (long life, separated motor)

o Ground water supply system, dual filters rinsed by manual turnign of valve, pressure instruments, freeze protection.  Had most of it.
o Connections on hot side of course, lots of tubing, cirk pumps, electric installation, small PLC.

Istallation time: one week for me and my father

Before, we used 8 cubic meters of oil per year, so in energy cost we will save almost cost of 6 cubic meters per year, or 3600 USD i think.  So not counitng interest (both oil furnaces we had was too old anyway) the investment will pay in 4 yeras, aftet that we just smile :)

Of course normally we would count installaiton work and interest too, still it will save a lot.  But note we had already a good well, that was once upon a time expensive.

/Morgan
--
Morgan Olsson, Kivik, Sweden

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2004\10\12@075216 by Morgan Olsson

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Russell McMahon 12:28 2004-10-12:
>New heatpumps plus installation tend to cost so much that the breakeven is often the better part of 10 years in a domestic environment.

In a lifetime 10 year a very short time.  You get much more interest rate of a correctly installed heat pump, than you pay for a normal investment loan.

I have a friend who have a heat pump from the seventies, still running as main heater.  So far only changed some *parts* of it.
And nowadays heat pumps quality is even better, although i guess you can always find bad quality pumps and installations...

/Morgan
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Morgan Olsson, Kivik, Sweden

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2004\10\12@083018 by Morgan Olsson

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Denny Esterline 13:22 2004-10-12:
>The cost per btu for electric is 2.5 - 3 times higher than
>the cost per btu of heating fuel.

Oh, I was just wondering why US have more then twice fossil fuel use per person than western europe...  Here fossil oil is just slightly cheaper than electric on average i believe.  

OK, so the most economic for you would probably be an diesel engine powered heat pump.  Well, the engine produce 70% of the fuel energy as direct heat, so connect the coolant heat hot water tank, and the heat pump need only pump to low temperature for heating.
...But still not as efficient as electric power, and more expensive installation.
( Probably a gas turbine and steam combi system can reach 60% mechanical power, but only feasable on large plants... )

Speaking about efficiency large heat pumps as used in town central sysems are made more complicated to achieve higher efficiency i have read, like:
1) lubricating oil not in freon circulaiton
2) pressure dropping valve replaced by turbine giving back some mechanical/electrc power

Some small heat pumps have frequency controlled compressor so instead of going on/off, it go continuously with reduced power, thus lower temperature drop in heat exchanger, thus lower pressure needed from compressor, thus lower input energy per output.  

I suggested that for my own system, but the manufacturer was afraid the lobricating oil might not circulate reliable with the freon when the flowrate of freon got reduced.  Better safe than sorry.

/Morgan
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Morgan Olsson, Kivik, Sweden

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2004\10\12@090843 by Denny Esterline
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> Denny Esterline 13:22 2004-10-12:
> >The cost per btu for electric is 2.5 - 3 times higher than
> >the cost per btu of heating fuel.
>
> Oh, I was just wondering why US have more then twice fossil fuel use per
person than western europe...  Here fossil oil is just slightly cheaper
than electric on average i believe.
>

Here in the US (Michigan), electricity is $0.08 - $0.10 per kilowatt.

Google says there are 3412 btus in a kilowatt hour. 3412/$0.10 = 34120 btu
per dollar.

I haven't priced it recently but assuming heating fuel is $1.50 a gallon
(low grade gas is $1.99 and heating fuel doesn't have road taxes applied to
it) and it has about 130,000 btu per gallon. 130000/$1.50 = 86666 btu per
dollar. Even at 80% efficiency rates for a burner (better is available)
that's just shy of 70,000 btu per dollar - half the cost of electric.

Then, as others have mentioned, you have to amortize the cost of the
equipment. An acquaintance of mine recently built a new house and opted to
install a ground source heat pump (loops of pipe buried in the back yard)
the *difference* in cost between a conventional furnace and his system was
more than $13,000. Of coarse math was never his strong suit....

-Denny


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2004\10\12@094250 by Gerhard Fiedler

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> The gas leaving the compressor is way over condensation temperature, thus
> by adding a small heat exchanger between the compressor exhaust and the
> condensation heat exchanger i can pull about 2kW @ 70°C while pulling
> 30kW @ 45°C main heat output.  (The high power is because is supplying
> two households)  The 45°C is for hous heating and first stage hot water,
> the 70°C is accumulated in a separate tank for final heating of hot
> water. Thus, even when taking shower i have very high efficiency :)
> (Values calculated by manufacturer, i can not measure but seem to
> corelate with experience from earlier weaker oil furnace)  On the
> electric side there is consumed (measured) : Compressor 8,5kW, Ground
> water feeder pumnp 1,2kW, Intermediate media circulaiton pump (cold
> side) 370W, low temp local house 45W; remote 370W, hight temperature
> tank 40W.
OT for this thread: You see the beauty of the SI? When power is W, wherever
it comes from and wherever it goes, and not W at one end and BTU/hr at the
other end? :)

Gerhard

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2004\10\12@102245 by Morgan Olsson

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Denny Esterline 15:13 2004-10-12:
>Then, as others have mentioned, you have to amortize the cost of the
>equipment. An acquaintance of mine recently built a new house and opted to
>install a ground source heat pump (loops of pipe buried in the back yard)
>the *difference* in cost between a conventional furnace and his system was
>more than $13,000. Of coarse math was never his strong suit....

Heh.

There are also occasions when heat pump can be a *lower* investment than oil furnace with all that comes with it included.

Depending on regulations, house type, and appearance, a chimney can be pretty expensive to build, plus it takes up indoor space.

A wall mounted air/air heat pump is about the same cost as just the chimney!
(And air/air pumps have very good efficiency spring and autumn, just not in very cold winter, but often total energy cost is stil better if additional resistive electric heat is added on rare occations when needed)

When a air/air heat pump is used, it is often economical to generate hot water completely separate by means of a heat pump pumping air from inside house, taking heat from that (same temp year around) /the swedish term is like exhaust-air-heat-pump, often combined with air conditioning system.

Theese two heat pumps above should normally not be more expansive than oil furnace+chimney+room for furnace and tank + oil tank + piping system.  - you get one free room in house for PIC junk ;)

/Morgan
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Morgan Olsson, Kivik, Sweden

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2004\10\12@184021 by Cnc002

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In a message dated 10/12/04 7:39:37 AM Eastern Daylight Time,
.....apptechKILLspamspam.....paradise.net.nz writes:

> Sombody has done something wrong somewhere, professional or not ! :-(
> As the hot water is just a heat source and as the other heat sources for the
>
> heat pump are liable to be colder than the waste water it just doesn't make
> sense. Obviously the professionals agree :-)
>
>
>

RM:

Yep, you have to set the thermostat on the hot water heater so that it is
LOWER than the output of the heat pump.  In the case of my system that is 125
degrees F. or a little lower.  When the water goes from the water heater tank to
the kitchen or the laundry room, it might be 100 degrees, if that by the time
it comes out of the faucet or into the washer.  That is just not hot enough to
do any good.  And, yes, the professionals did agree that if I wanted water
that was more than just "warm" the recovery system would not work.  It was free
and so was the installation so I didn't worry about it and just turned the
blamed thing off.

By the way, the heatpump system I have is over 10 years old and is rated
something like 85% efficient, not up to the current standard but it still does a
good job and, as I mentioned earlier, it costs me less than any of my neighbors
on natural gas.  It cost me $4,400.00 USD for the unit and installation.

Randy Abernathy
4626 Old Stilesboro Road NW
Acworth, GA 30101-4066
Phone / Fax: 770-974-5295
Cell: 678-772-4113
E-mail: EraseMEcnc002spam_OUTspamTakeThisOuTaol.com
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2004\10\13@000410 by Denny Esterline

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> >Then, as others have mentioned, you have to amortize the cost of the
> >equipment. An acquaintance of mine recently built a new house and opted
to
> >install a ground source heat pump (loops of pipe buried in the back
yard)
> >the *difference* in cost between a conventional furnace and his system
was
> >more than $13,000. Of coarse math was never his strong suit....
>
> Heh.
>
> There are also occasions when heat pump can be a *lower* investment than
oil furnace with all that comes with it included.

I agree, but in the aforementioned case the system also has a redundant
propane furnace- so he paid all the costs - twice.

> Depending on regulations, house type, and appearance, a chimney can be
pretty expensive to build, plus it takes up indoor space.
>

Definitely. Around here though it's common to run the flue up the outside
of the house and box it in with siding. And modern high efficiency gas
appliances actually use a plastic flue and vent near ground level.

> These two heat pumps above should normally not be more expansive than oil
furnace+chimney+room for furnace and tank + oil tank + piping system.  -
you get one free room in house for PIC junk ;)

I never thought of that, I cal the HVAC guy tomorrow... :o)

-Denny


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