Author Topic: Heat Pump intermittent start-up issues  (Read 2761 times)

Offline Daniel

  • ***
  • Posts: 2
Heat Pump intermittent start-up issues
« on: September 27, 2015, 03:47:49 PM »
Hello,

I am not a HVAC technician so I may not know all the terminology, however I am handy with electronics and I am comfortable doing repairs.

I have a Carrier 38YCC024340 heat pump that is a little over 13 years old. About 6 months(at the end of winter) ago we had an HVAC technician come in and do maintenance. While he was here, we got a new thermostat(A honeywell RTH7600D1014) put in.  Everything seemed to work ok until summer. During one particularly long heat wave the heat pump stopped working. When I say it stops working, the fan does not spin and it makes a fairly loud buzzing noise and nothing is being blown through the vents. When this happens we turn the heat pump off at the thermostat, go outside and flip the outside switch there and then flip the breaker in the house, so no power is going to the heat pump.

We called in another HVAC company and that technician looked at the thermostat installation and told us that it had been installed incorrectly - backwards as he put it. From what I understand when the heat pump was getting the cold signal it would send in heat and when it got the heat signal it would send in cold. We didn't notice this before, but when he fixed this the heat pump worked and he was on his way, costing us around $100.

Shortly after the heat pump stopped working again. We called the 2nd HVAC guy back and he said it was a fan issue. He replaced the fan and all was well when he left. This cost around $300.

The next day the heat pump stopped working again. We called the technician back and he opened up the heat pump to a controller board, as he took the controller board out the heat pump started working. He said it must be the relay on the circuit board. He replaced the circuit board and the heat pump was working when he left. This cost us $400.

Later that day the heat pump stopped working. We called him back and when he got here we turned on the heat pump and it was working. Perhaps it is a shut off in the condenser coil that detects if it is too hot and is shutting it off. This doesn't sit well with me as the heat pump can be disconnected all night and when we turn it on in the morning sometimes it doesn't work. Regardless, he told me that when this happens to disconnect the power to it, remove the fan and put my hand on the condenser to see how hot it is. This trip cost us $100. This is where I am now. I have put my hand on this condenser and it is warm, but not overly hot. I can keep my hand on it for as long as I want and it doesn't burn me.

The technician has hooked up some kind of meter to it and said that the levels all look ok, and he's not sure what is happening. I'm just not into feeding these guys any more money, I have spent $1000 on repairing this thing and it is still broken.

Does anyone have any suggestions for this? When it is not working, there is a loud buzzing coming from the heat pump. When I turn off the outside switch to it, the loud buzzing stops but there is still a light buzz that comes from it until I turn off the breaker. I have also turned off the system from the thermostat, turning off the heat and AC and put just the Fan from auto to ON. Nothing happens, the fan does not spin and the buzzing does not stop.

Any help would be appreciated.  Thank you.

Offline Daniel

  • ***
  • Posts: 2
Re: Heat Pump intermittent start-up issues
« Reply #1 on: September 28, 2015, 11:01:00 AM »
We're changing the thermostat on this today.

I feel like the HVAC technicians are just throwing shit at the wall to see what sticks.

Luckily the thermostat was under warranty and we got a new one for free. The HVAC guy is coming in to do the wiring. I could do it myself but I don't want the blame to be shifted to me for this thing not working. It's still going to cost almost $100 to get it installed.

I know this is a hard issue to diagnose on a forum. I was hoping that a technician might have seen this strange issue and give me an answer right off the hop.

We've decided that if changing the thermostat doesn't work, we're cutting our losses and putting in a new heat pump. I am pissed at the HVAC "professionals" we've hired. Over $1000 in services calls and parts later and the heat pump works the same as it did 2 months ago before we called them. It doesn't. I really don't know how these technicians can look us in the eye and ask for money for the calls they are making. They won't even take the parts back, so we've paid for parts that didn't fix the problem with no recourse. I am thinking of taking these guys to small claims court to at least get some of the money back. I could have done all the work they did and I would have just paid for the parts, and not the $80 an hour calls.

Offline Admin

  • Administrator
  • *****
  • Posts: 2363
    • HVAC TECH GROUP
Re: Heat Pump intermittent start-up issues
« Reply #2 on: September 28, 2015, 12:33:12 PM »
It sounds like the 2nd technician misdiagnosed the faulty condenser fan motor and circuit board, because the problem is still happening.  It's possible when the tech touched the control board he thought it was the relay sticking, but it really could have been the contactor sticking.

Quote
Does anyone have any suggestions for this? When it is not working, there is a loud buzzing coming from the heat pump. When I turn off the outside switch to it, the loud buzzing stops but there is still a light buzz that comes from it until I turn off the breaker. I have also turned off the system from the thermostat, turning off the heat and AC and put just the Fan from auto to ON. Nothing happens, the fan does not spin and the buzzing does not stop.

So outside you turn off the disconnect which stops the 240V.  Which breaker are you turning off that stops the light buzz?  The furnace breaker?  That would be 24V and the buzzing is probably coming from the contactor inside the heat pump.  When you turn the thermostat fan ON, the indoor furnace fan should start running, but the fan in the heat pump outside should not run if the fan is turned ON at the thermostat.  It should only run if there is a call for heating or cooling.  If the thermostat system is set to OFF, then the buzzing can't be the 24V.  This must be the loud buzz you hear, that is being caused by the 240V.

I would have tested the capacitors and tried replacing the contactor myself.

Offline Trainerguy

  • G2 Supporter
  • ****
  • Posts: 23
Re: Heat Pump intermittent start-up issues
« Reply #3 on: September 28, 2015, 07:37:11 PM »
The buzz you are hearing is probably the 24v coil in the contactor energized and pulling in the contactor. I am wondering if it is a problem with the contactor itself, the contactor is sticking some times and the unit won't start or as the unit is quite old it could something as simple as an earwig or bug stuck between the contacts not allowing the 240volts reach the motor and compressor intermittently.
I think it is going to be something simple. Good luck.

Trainerguy