What can cause the indoor coil on a heat pump to vibrate loudly when in heat mode?
We had our leaking indoor coil replaced a few weeks ago. Last night was the first time that it was cold enough outside (52F) to use the heat pump in the heat mode.
The system sounds normal at first, but over a 60 second period the indoor coil / housing begins to vibrate louder and louder. It vibrates at the same frequency as the sound coming from the compressor in the outdoor unit.
I think it is the coil / housing (and not the blower) because the instant that the compressor shuts off, the indoor coil stops vibrating completely while the blower continues running at the same speed, but very quietly.
Also, the system has been working normally in the cooling mode. No unusual noises. It also works normally, quietly in all blower modes and in the gas heat mode.
We have a Goodman air-source heat pump (GSH130421). The indoor coil is CHPF3642D6.
The unit is suspended from the floor joists under the bedroom/hall. The vibrations are transmitted to the floor and walls in that area and is actually a little louder (if you stand in that spot) than the sound of the outdoor unit, which is just outside the bedroom wall.
Thanks for your help.