View Full Version : capillary tube heat pumps and bi directional filter driers in liquid line

08-08-2013, 12:54 PM
Hi all,

With a capillary type heat pump, will a bi directional filter/drier installed in the high pressure line at the outdoor unit end affect the system's operation? From what I can see, there is one capillary tube metering device in the outdoor unit. As far as I understand - depending if you are in heating or cooling mode there may be liquid refrigerant or liquid/gas flowing through the filter/ drier if installed......just checking with those more learned than myself on the theory and suitability of using such a unit to filter out moisture etc.

Any thoughts would be much appreciated.

The MG Pony
08-08-2013, 07:26 PM
I think in a prebuilt style system be best to use a standerd unit with a check valve so it opperates in only one mode for simplicity and ensurance of correct opperation. that or use a suction side drier befor the diverting valve.

Rob White
09-08-2013, 12:08 AM

The Bidirectional dryer will work but be aware that most
heat-pump systems use a check valve and an extra capillary
tube in the heating mode.

The simplicity of the capillary does not allow for the condenser
being bigger than the evaporator, so the extra bit of capillary
in heating mode reduces the efficiency of the condenser when
acting as the evaporator.