Intermittent heat pump operation

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Old 02-04-15, 07:04 PM
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Intermittent heat pump operation

Trying to help a neighbor troubleshoot his HVAC system. He has a Honeywell t-stat (one year old), an Airflow heat pump (also one year old) and a 28 year old Goodman air handler. His heat pump has not been heating and instead the aux coils have been running. I removed the t-stat from the wall and jumpered the R wire to the W and the heat pump did not turn but the unit made a clicking noise. I then jumpered the R to the Y for cooling and the heat pump turned on then off a short time later. I jumpered the R to the W again, went outside to check, and there was only a couple volts on the orange wire and a couple volts on the red wire (I was expecting 28). When I had the cover off, the heat pump turned on all of a sudden and there was then 19V on the orange wire and 19V or so on the red wire. The heat pump turned off again and then there was 28V on the red and 28V on the orange (remember I jumpered these two wires together at the t-stat). However, why would there not be voltage on these wires when I first checked, then all of a sudden there was when the heat pump turned on (19V), then 28V like I initially expected to see? Arent the wires from the thermostat connected to the same color wires going to the heat pump? If so, it doesnt make sense not to have seen 28V. Maybe the air handler control board or heat pump is pulling the voltage down? The heat pump is brand new so I suspect the air handler, but I suppose the wires from the air handler to the heat pump could be damaged. BTW, the diagnostic LEDs inside the heat pump said everything was normal for the most part, but indicated a high pressure fault after running for a couple minutes in the cooling mode (red wire jumpered to yellow). Any ideas?
 
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Old 02-04-15, 07:27 PM
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Jumpering the R to W activates the electric coils.

You need to connect R to Y and O at the same time. Y is the compressor and O is the reversing valve.

A high pressure fault is caused by lack of airflow thru the inside coil. Make sure filter is clean as well as returns aren't blocked and not too many registers are closed.
 
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Old 02-04-15, 08:25 PM
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I thought W2 was the heating coils? Regardless, the heat pump isn't turning on when the t-stat is set to heat and there is 28V at the air handler and t-stat but not consistently at the heat pump. That alone indicates a problem with the wiring doesn't it? BTW, he just had his basement finished a couple months ago and I'm wondering if the drywall guys accidentally drove a screw through the wires. He isn't sure how long the heat has been running off the coils but it has been in the last several weeks.

Wait a second. The wire connected to the W is orange. Shouldn't the white wire be connected to the W and orange wire to the O terminal? I'm pretty sure the white wire is connected to W2. I'll have him snap a photo tomorrow. Now I,m wondering if his heat pump ever worked properly since it was installed last January.
 

Last edited by mossman; 02-04-15 at 08:40 PM.
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Old 02-04-15, 08:57 PM
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Think I was looking at the "Conventional" labels when I should have been looking at the Heat Pump side of the connector. W on Conventional corresponds to O/B on the heat pump side. So I think the t-stat wiring is correct, but still think maybe something happened to the wiring between the handler and the heat pump. I'll have to do some continuity tests with the wires disconnected.
 
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Old 02-04-15, 09:07 PM
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You are correct.. on that stat W=O/B and W2 is the electric heat.

You received the high pressure fault since you had the compressor running but no blower inside.

I'm trying to figure out what you have going on there. If there was a screw thru the wire the fuse should blow or the transformer should burn up. Something is drawing enough to cause the voltage to sag but not enough to cause damage.
 
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Old 02-05-15, 06:00 AM
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I'll disconnect the wires at the heat pump and the air handler and see if I have any partial opens or shorts. Maybe there is a partial short between the orange (heat) and yellow (cool) wire leading to the heat pump. I'll report back witb my findings.
 
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Old 02-06-15, 01:50 PM
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The HVAC technician said there's a freon leak in the air handler (must be pretty minor) and the control board on the heat pump (less than one year old) is bad. The control board is under warranty so there is no charge, but he said $3,000 to replace the air handler, which seems pretty high. Not sure what brand. If the leak in the air handler is major, wouldn't the outdoor condenser coil freeze up? I know if you have a leak and run the A/C that the indoor coil will freeze up, but I'm not sure if the opposite is true (mine indoor coil doesn't freeze up, I'm speaking hypothetically).
 
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Old 02-12-15, 07:44 PM
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Tech replaced the heat pump control board and now things are working properly again. Vents are blowing harder and basement return has more suction. Don't quite understand how the heat pump affects the blower speed. I suppose the bad control board was loading the circuitry down and not allowing the motor to spin up fully.
 
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