I just finished installing a Heat Pump (48.000btu/h Carrier Infinity) for a client. It ended up with 90ft refrigerant lines. The install guide says to install a solenoid valve on the liquid line at the outdoor unit IF THE LINES ARE OVER 100ft LONG. I asked my distributor tech "Why"? and would I get better performance somehow if I put a solenoid valve in the liquid line in a system with 90ft lines. I was told "Just do it like the manual says". So I did not install a solenoid valve and all seems just fine.
So.. The system is working fine, but inquiring minds want to know the Why an added liquid line solenoid valve is needed if the tubing is over 100ft. The only thing I can come up with is that, since the system has a flow restriction orifice at the outdoor unit (instead of an expansion valve) that liquid will flow into the outdoor unit during idle times without the solenoid valve. But this will happen with short lines and long. Does the system start up faster if the solenoid valve is used? Or is there a danger of there being enough liquid to get back into the compressor and damage it on long lines without the solenoid?
Thanks for any insights!
Joe
My guess would be what you already mentioned. To prevent the liquid refrigerant from damaging the compressor.