"water hammer" in line set
Heat pump is doing this when the unit shuts off in heat. Does not do this in cool when the comp shuts off. Reversing valve energized in cool.
Customer had a dirty ass filter and that dropped the high side pressure from 350 to 250 (during heat mode) on filter change... i noticed that the unit seemed a little low on refrig since 7* SC in 50* ambient (in cool mode). Added 2lbs of R-22, got the SC to 10* (in cool mode).
Anyway, with the pressure drop the "water hammer" is less prominent. Just started doing that this season. Also found a leak at the TXV distribution tube fitting.
Does low charge cause this due to lack of column of liquid?