Heat Pump Design

[behmin]

Can anybody tell me that for active defrost in heat pumps (reversing the cycle to defrost the frost/ice), there will be absolutely a requirement for accumulator. The compressor for the heat pump system is scroll. The heat pump is a water to air system. Evaporator is heated by ambient air and condenser is cooled by water.

[nike123]

No, there is no absolute requirement for accumulator if total charge of system is not higher then compressor manufacturer recommends.

[yangchenchen]

Certainly, there is absolute requirement for accumulator. Because the plate heat exchanger can only contain a little liquid refrigerant, and the working conditions in different seasons vary a lot. So there must have a accumulator to contain the surplus refrigerant that is not needed in refrigeration cycle during lower loads.

[nike123]

Certainly, there is absolute requirement for accumulator. Because the plate heat exchanger can only contain a little liquid refrigerant, and the working conditions in different seasons vary a lot. So there must have a accumulator to contain the surplus refrigerant that is not needed in refrigeration cycle during lower loads.

Nothing is absolute:

Accumulator is considered a Copeland
specification requirement on all air source heat
pumps unless slugging and floodback test under
low ambient and defrost conditions are run and
satisfactorily passed to prove that operation without
an accumulator is acceptable.

http://www.hvacrinfo.com/cope_ae_bulletins/TAE1243.PDF

Every model compressor recommend the refrigerant mass charging .

No, there is no absolute requirement for accumulator if total charge of system is not higher then compressor manufacturer recommends.

[taz24]

Certainly, there is absolute requirement for accumulator. Because the plate heat exchanger can only contain a little liquid refrigerant, and the working conditions in different seasons vary a lot. So there must have a accumulator to contain the surplus refrigerant that is not needed in refrigeration cycle during lower loads.

Accumilators in the suction line are not absolute if the system is sized corectley.
They tend to have them fitted with heatpumps because the cond will be larger
than the evap and when on reverse cycle there is the possiblity of liquid flooding
back to the comp. Some systems use TEV's and some use Capilaries.
They all require different requirements. TEV's need liquid storage, whether that
is in the receiver or backed up in the condenser. Capilaries need to be critical charged.

It is horse's for course's and you can never say you absolutly need do do somthing.

taz.

[nh3wizard]

Certainly, there is absolute requirement for accumulator. Because the plate heat exchanger can only contain a little liquid refrigerant, and the working conditions in different seasons vary a lot. So there must have a accumulator to contain the surplus refrigerant that is not needed in refrigeration cycle during lower loads.

I guess my heat pump at home was manufactured wrong because there is no accumulator on it. Just kidding, there is no requirement for a accumulator for a heat pump, its up to the manufacturer and the the design of the heat pump.

[desA]

No, there is no absolute requirement for accumulator if total charge of system is not higher then compressor manufacturer recommends.

Do you perhaps have links to what a Copeland would recommend as total system charge, for Copeland scroll series compressors?

The ZR & ZH series in particular.

[nike123]

Do you perhaps have links to what a Copeland would recommend as total system charge, for Copeland scroll series compressors?

The ZR & ZH series in particular.

I think that i stated in catalog, but I need to check.

[desA]

^ Thanks very much.

[nike123]

Some information could be found here!
http://www.hvacrinfo.com/ae_index.htm

[desA]

Thanks so much for the link - that is incredibly helpful. Much obliged.