Any Heat Pump experts here? (1 Viewer)

[Shawn C]

I've got a problem with one of my Daikin multi-zone heat pumps. My house has 4 of these units feeding A/C to 12 individual units throughout my house.

Anyways, I noticed that 3 of my units have quit blowing cold air and they are all connected to the same heat pump. (The in-house units have their own power and will just run the fan even if the heat pump isn't working..)

I have isolated which one of my 4 heat pumps isn't functioning.

I noticed that it looks like the compressor itself isn't turning on. The fan on the unit is not turning on either. I have checked the fuses and the breakers for the heat pump and they are all ok.

Could this simply be a refrigerant problem? If the unit is low on freon, will it turn on? Is it like an automobile compressor where the A/C clutch won't engage when the freon is low?

I am selling the place in a few months probably and don't want to go through the expense of a new unit if I don't have to. (I am going to offer to pay for a homeowners warranty on the house anyways...)

Any ideas? Also, I'm pretty sure the unit is around 16 years old.

 

[Craig]

HVAC Forum

 

[Philip_G]

I think it really depends on the unit, some of them have low pressure switches and some don't. An older unit I'd say likely won't, but that's a guess.
The condenser fan isn't running? Is it fused outside or a breaker? Did you check the breakers at the panel as well? click them off and then back on (for the heat pump)
Can you hear any buzzing coming from the unit when it's calling for cooling?
it could be a bad contactor, problem in the control wiring, blown fuses/breakers, a million things really

 

[Shawn C]

Thanks, I didn't know there was an HVAC forum. I just posted a similar message there.


It's fused on a small sub-panel right next to the unit. I pulled the fuse block out and the fuses check out, as far as I can tell. When I put the fuses back in, I can hear a click in the unit, so I assume it's getting power.

 

[Philip_G]

there's two of them though.
You need to test across them with a multimeter to be certain they're OK

 

[Todd Hochard]

Try this-

Open the breaker or pull the fuse pack for that compressor to remove power. Wait a couple of minutes. Make sure the thermostat inside is set to make the unit come on.

Power it up, and immediately get next to it. Listen REAL close at the compressor and fan on top. Can you hear a hum? Stand there for a few minutes? Do you hear a click, and hear it go away?

If yes, then something is causing a thermal overload. See if the fan spins freely by hand. Does it? Obviously, you need to watch your fingers here!

If neither the compressor nor the fan on top want to spin electrically, but do mechanically, and you can hear the hum of power being applied initially, the most likely culprit is the start/run capacitor. Give it a look over, and see if all the dielectric leaked out. They seem to explode after some years of run time.

If that isn't it, there may be a schematic inside the compressor. With that and a voltmeter, you might be able to narrow down what's going on.

I'm not an HVAC tech, but I play one for my friends and neighbors who seem to have this problem more often than not.

What sort of a house has FOUR heat pumps?? A big 'un, I guess.

Todd

Standard Disclaimer- be careful poking around in there. 240VAC can KILL YOU, and hurts in any case. Make sure you are de-energized before removing any components.

 

[Philip_G]

Problem is there's a start and run capacitor for the compressor, and a seperate capacitor for the condensor fan. If he has a multimeter with the ability to test the capacitors it's a quick process, but I wouldn't expect that to be the problem as neither are running.

Granted, it's been about 10 years since I've worked on a heatpump so...
the click he mentioned is probably just the contactor getting pulled in from the T stat..
you could pull the service panel and push the contactor closed with a screwdriver (be careful here) and see if she'll fire off to eliminate a control problem, though it sounds to me like something else.