Loud humming noise from Heat Pump

Forums › Home Workshop DIY › Loud humming noise from Heat Pump

Shanemc

76 posts

Master Geek
+1 received by user: 14

#260054 8-Nov-2019 12:57

Hi wonder if I could tap into some collective wisdom/experiences.

We have a panasonic multi-split heat pump system. With 3 high-wall head units.

It is coming up 4 years old.

Last summer one of the high wall units developed an intermittent rough electrical/humming sound. This sound would usual last about 30 seconds then stop. It would sometimes happen every 5 minutes, then sometimes not at all.

It does not seem to be related to the fan, and it is quiet a bit louder than the normal fan sound when on quiet.

The difference between this unit and the others is that it has a condensate pump.

The sound does not occur when the unit is used for heating, so we have not had it for the past 8 months.

But turned the unit onto cooling a similar thing happened. Although this time the sound continued after the unit was switched off. In fact started up about 15 minutes later. I had to turn the isolation switch off.

The unit is in my daughter bedroom and used at night. So it needs to be quiet.

We had a person have a look at it yesterday, but they did not seem that experienced and did not know what the problem was, and of course it wasn't making the noise.

I wonder if this sounds familiar to anyone else?

I suspect it is something to do with the condensate pump, but not sure how to test that or if they can be isolated.

Cheers for any help.

RunningMan

9186 posts

Uber Geek
+1 received by user: 4840

#2350248 8-Nov-2019 14:39

Almost certainly the condensate pump from what you describe. It will only be needed on cooling, and will cycle on and off - more frequently the more humid it is.

SomeoneSomewhere

1882 posts

Uber Geek
+1 received by user: 1086

Lifetime subscriber

#2350872 9-Nov-2019 21:40

Try pouring water into the drip tray (SLOWLY). This should trigger the condensate pump.

You should be able to pull a cover off to see the water tank in it.

Often they are loud while priming, then much quieter when properly primed. Feed a cup or so through it and it might quieten up if that's the issue.

Kickinbac

468 posts

Ultimate Geek
+1 received by user: 93

#2351333 10-Nov-2019 23:36

Condensate pumps only work in cooling mode as the cold indoor unit coil condenses the moisture out of humid air. Most have a float switch that turns the pump on as the reservoir fills up with condensate. There are some that work on a temperature sensors. I’ve always had a rule not to use condensate pumps in residential installs because they always make noise, especially annoying at night when its hot and want to sleep. This is why most installations of hi-wall units are on exterior walls so the refrigerant pipes and drain get to outside easily. Only way to solve it is to change the drain to gravity drain but may not be possible in your situation.