Knocking noise in system

[paulv]

We are looking at a Rheem system, heat pump. When it cycles off it begins a knocking sound after approx 3 min. Goes for 60-90 sec, slows down and then stops. It sounds like metal on metal. We have some ideas but are looking for input.

[ASHLEYHVAC]

Need model # and serial # of unit.

where is the noise coming from?

[timjimbob]

How long is lineset and evap and condenser same elevation?

[jpnatlanta]

Same issue last week on a Weather King (Rheem). Knocking was at outdoor TXV after shut down. All operating values were normal. This being an investment property with the owners wanting "the cheapest fix", installed a solenoid valve in the liquid line. Problem was solved.

[timjimbob]

TXV=$70, Solenoid= $120. Cheaper? Guess less labor on Solenoid.

[BaldLoonie]

Rheem knows about it. Likely will need a bleed type TXV put in the outdoor unit. Even then, might not stop it. We're 1 out of 2. I'll ask our tech rep about the solenoid idea.