Heat pump makes trumpet sound coming out of defrost when it is below 32 degrees outside

SOURCE: Ruud heat pump UPKA 036JAS,

probably just the defrost cycle, or could be pressure equalization

Dale Koehn

• 88 Answers
• Posted on Jan 24, 2009

SOURCE: New 14 seer split ruud heat pump makes very loud knocking noise

Well you may want to have a tech come out and check the freon level, but mostly when going into defrost, some units make alot of noise, the freon is reversed in the unit by way of the reversing valve, it makes a whooshing sound like freon is draining off, as far as the knocking noise, could be as I said in the beginning, might be low on freon, but it could be that, this particular unit does this, I have had units make some really strange noises in the past but functioned perfectly, hope this helped, please let us know, thanks again,
mr.grzz

SOURCE: Carrier PTAC Condenser ices over.

You are describing normal operation for a heat pump unit.

SOURCE: Heat Pump Cycles On and Off and Air Handler Noisy

I am pretty sure you have a low charge and the pressure switch is kicking it off. probably just a pound or two however the accumulater will sometimes hold more.

SOURCE: heat strips do not energize during defrost cycles

if your heat strips are not coming on, then there are a few things to check.

The first one would be that the heat strips are actually working. The easiest way to complete this task is to turn the system on into emergency heat and turn the thermostat up. If you get heat accompanied by the traditional strip heat burnt smell, then you know the electric heat strips are working.

The second thing would be that the air handler is receiving a command for heat during defrost cycle. If the command is present with no heat, then you most likely have either a wiring issue or a failed electrical relay or contactor.

The third thing would be the defrost board itself, for it is the component that calls for electric heat strips to come on during a defrost cycle. You may or may not be able to force the defrost board into a defrost cycle and then check that the heat strips are on or not.



It sounds as though your defrost board is bad with the symptoms you are describing.

Good luck.