Got a call from a client today about an odd noise that started this heating season. I went out to the house to see what I could find.
Background: House is 4 yrs old. HVAC system consists of 3 ton heat pump down with gas backup Upstairs is 2 ton heat pump.
When the upstairs thermostat calls for heat, the outside unit starts slow (like it’s really working hard or almost dragging and way more than the larger heat pump right next to it, then comes a loud thud (could be a very fast vibrating sound) inside the wall of the master bedroom. It’s loud enough that it’s waking them at night. The outside units are at basement gound level and the bedroom is first floor. The line sets almost surely run up the bedroom wall and accross the master ceiling and then on up to the air handler that is over the 2nd floor ceiling.
HVAC tech checked the coolant levels and all are normal. The noise only occurs when the heat pump has been idle for an undetermined amount of time. After the initial start up, the system doesn’t make the noise on subsequent on off cycles. It has to sit for an hour or so before the bang happens again.
I’m guessing the line set is vibrating inside the wall for some reason but I’m looking for confirmation or ideas as to what could be causing this and how to proceed from here.
Thanks!
kcoyner
Replies
Several yrs ago..........
We had a unit that was making a vibrating noise on start up in a commercial office setting.
All I remember was there was a "soft start" thing that went on the fritz. Not much good on the technical advice but it might suggest a place to check.
Best of luck.
Sounds like the accumulator valve is sticking. Have the HVAC tech check the super heat in addition to his guage pressures. Changing the filter/drier may be enough to get the junk out of the line set and solve the problem.