Heat pump refrigerant circuit - bypass filter drier and liquid receiver in defrost

[skysurfer81]

At the moment i´m building a diy heat pump - It´s a compact unit (non split) and at the moment i design the refrigerant circuit for it.

I´ve looked at some manufacturers and they have bypassed the expansion valve and filter drier with a liquid line and check valve.

Does anybody know why?

[AlexG]

This is because of one-way TXV and filter drier.

[skysurfer81]

I saw it also with a biflow eev. did something happen when it´s going through the filter drier?

[skysurfer81]

beispiel.jpg

But why they doing it?
It´s an full biflow eev and biflow filter drier

[AlexG]

what is 13? Check valve?

[skysurfer81]

Yes --- Danfoss NVR6 - Check valve

[skysurfer81]

Its from an air water source heat pump

[AlexG]

and what is flow direction? Up or down? It opend on cooling or on heating?

[skysurfer81]

open direction is down / cooling (defrost)

[AlexG]

If it is reversible unit (I mean it can work in heating and cooling mode), I dont know what is this. If it is heat pump with defrost, I can assume this is like capillary tube in frige, because filter-drier is after EXV. It is too high resistanse for liquid/gas mixture. In your case you dont need it. More important is liquid separator on suction line.

[skysurfer81]

Hello Alex... i think it´s also different what type the heat pump is.

Reversible only for defrost and Reversible for heating and cooling?!

I saw also some example that there is a second valve is installed. But between is the liquid receiver and filter drier.

?!

If it is reversible unit (I mean it can work in heating and cooling mode), I dont know what is this. If it is heat pump with defrost, I can assume this is like capillary tube in frige, because filter-drier is after EXV. It is too high resistanse for liquid/gas mixture. In your case you dont need it. More important is liquid separator on suction line.

[AlexG]

If it is solenoid valve I can guess before defrost warm liquid is pushed to cold coil to start defrost before compressor start to improve defrosting. If u have piping schematic diagram of mentioned heat pump.