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Thread: DIY heat pump 12kW
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12-06-2007, 09:38 AM #1
DIY heat pump 12kW
Hello to all,
I am new to the forum and already found and read a lot of good information.
I want to build water to water heat pump about 10-12kW. I have knowledge in assembling, automation etc, but not in selecting components. I plan to use Copeland ZH compressor and Swep plate heat exchangers. I have downloaded Copeland's selection software and have some questions about selecting operating points. My water source has about 5-10 deg. C and I will use heat pump for underfloor heating. I will also use inverter to control heat pump power (control compressor's rpm).
My questions (for start ) are:
1. what should be evaporating temp. and superheat?
(My guess is 5 deg. C and 5 deg. C. superheat)
2. what should be condensing temp. and subcooling?
(My guess is 35 degC so I go with 30C to underfloor heating)
3. I want to use heat pump also for domestic water heating (55deg. C)
Does it mean I just divert heated water to the domestic water tank and leave it circulating until it reaches 55 deg. C?
Regards and thank you for your help!
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13-06-2007, 03:09 PM #2
Re: DIY heat pump 12kW
The lower the evap temp the more chance of freezing the water.
Use brine / glycol to alow you to run the suction as low as you want.
Just leave the superheat set to the factory setting. If you do adjust set to about 6 to 8K
Condense about 8 to10deg higher than your intended water temp. For floor water needs to be about 27 to 30degC
For hot water, well then thats up to you. You could run a coil through your hot water tank before you then go to the heat exchanger. This will then desuperheat the refrigerant and heat up the water to between about 50 and 60degC. then the cooler refrigerant could heat water in your floor loop. You do need to be aware of legonella so you need to be able to take the water to about 60C on a regular basis.
Hot water does not need to be too hot if you intend to just cool it down to use in sinks or baths.
Yes see above.
Cheers taz.Last edited by taz24; 13-06-2007 at 03:23 PM.
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19-06-2007, 08:42 AM #3
Re: DIY heat pump 12kW
Taz, thank you for clarification. I think I will buy ZH21 compressor from Copeland.
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19-06-2007, 09:38 AM #4
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20-06-2007, 08:50 PM #5
Re: DIY heat pump 12kW
Well, I don't have ground water yet. I am planning to make deep well - about 25 meters of 4inch pipe. My neighbour has plenty of water which was found on 21 meters, then it rised to 15 meter.
Plans are for end of june. I'll keep my fingers crossed
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22-06-2007, 11:30 PM #6
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23-06-2007, 01:04 AM #7
Re: DIY heat pump 12kW
Ground source heat pumps seem to be the way forward using a secondary circuit. Don't forget to consider the use of antifreeze in the system
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23-06-2007, 07:42 AM #8
Re: DIY heat pump 12kW
Or making two wells of the same depth, one for pumping out the water and one to reject the water again in the ground.
It's forbidden in Belgium to use ground water in an open circuit for cooling or heating purposes.
If everybody should do it this way(only one well), then the lower subsoil water layers aren't disturbed any longer.It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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17-07-2007, 10:06 PM #9
Re: DIY heat pump 12kW
We tried to bore 33m and no water. And 100m away from me all the neigbours have plenty of water 4m below ground.
Now I am considering about air-to-water heat pump.
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08-03-2008, 04:44 PM #10
Re: DIY heat pump 12kW
Hi don,t worry, go ahead with the air to water unit, you will only need a very good defrosting system. I don,t know what your plans are, but you have to think of an air to water system with a termal storage system that can help to defrost if the need comes. Till then it,s good luck.
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08-03-2008, 05:00 PM #11
Re: DIY heat pump 12kW
that or over size your out door coil considerably and use an inverter controled fan to keep the SH constant.
IE program a control with a pressure transducer & thermister to slow the fan if SH gets too high or speed the fan should sh get too low
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17-10-2009, 07:50 PM #12
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