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gdidi
27-06-2007, 11:48 AM
Dear RE Members.

I am absolutely new to the in-depth workings of refrigeration systems. I understand the basic principles.and have some experience in the electrical control of HVAC systems.

I am considering the possibility of using my Mitsubishi heatpump to heat (Pre-Heat) my domestic hot water.

I have a 16KW (heating multisplit) unit
Model MXZ-8A140VA
REFRIGERANT R410A

The cylinder I have has a stainless steel coil inside the tank.

The coil has a surface area of 1,1M2(Square meter)
Diameter of 20mm
I think this has a KW Rating of more or less 32KW

My Question is:
If I were to turn all other circuits OFF and dedicate the total capacity (16KW) to this coil will it work as a water heater?

What possible problems could I face

Once I receive some answers/suggestions I will ask a few more questions.

Thanks for your reply in advance.

The MG Pony
27-06-2007, 04:55 PM
Do you all ready have a hydronic heating system? For a well made under floor hydronic system you only need water of 35C. At 35c constant flow of a 5c swing your heat pump will handle this no problem, as will most systems, I my self am making a 5Kw hydronic heating system via a coaxial exchanger (Plate will be much better for this how ever).

For domestic hot water the max temp will be 40C, too low for health codes due to Legionnaires disease if I recall correctly, the system must reach 70C.

If you go into the heat pump section you will find better info, take a look at my project too for some ideas along with some others there.

marianstancu
23-07-2007, 08:58 AM
The heat pump utilisation is O.K. for low temperature hydronic systems (35 - 45 Celsius). That means underfloor heating and ventiloconvectors (fan coil units).
If you want a higher temperature it`s possibile to opperate at 55 (max. 60) Celsius deg., but the COP will be lower.
For DHW, i recomand you to use a tank with two coils. First for water preheating (up to 40-45 Celsius deg.) with heat pump and the second will be conected to a boiler to give 55-60 Deg. and also for antilegionella !

squil
13-09-2007, 09:28 AM
Most heat pump manufacturers include domestic water heating, so it's perfectly feasible but COP will drop.
For Legionnaires disease I think the system must be able to reach 70 °C but only temporarily. An electric resistance can be used...