Trane XE 900 shorted
#1
03-05-05, 01:41 PM
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Trane XE 900 shorted
Hi all!
To make a long story short, my breaker for my compressor kept tripping.....further investigation found that there was a direct short between both poles at the compressor somewhere (on the compressor side of the local disconnect). I troubleshot it all the way down to the contactor. After lifting some wires that were parralleled on the contactor that were routed into the unit somewhere, the short went away. So the contactor checks out ok. I'm not shorted to ground. What inside the unit could cause this?
Any ideas?
Thanks!
Tony
To make a long story short, my breaker for my compressor kept tripping.....further investigation found that there was a direct short between both poles at the compressor somewhere (on the compressor side of the local disconnect). I troubleshot it all the way down to the contactor. After lifting some wires that were parralleled on the contactor that were routed into the unit somewhere, the short went away. So the contactor checks out ok. I'm not shorted to ground. What inside the unit could cause this?
Any ideas?
Thanks!
Tony
#2
03-06-05, 06:21 AM
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Check the compressor teminals themselves, if they are shorted to the compressor housing or you don't get continuity through each one it's time for a service tech to go any further.
Make sure the disconect is pulled and with you while checking so no one turns it on while you're in there. But if the short to ground is bad enough to trip the breaker there's probably nothing you're going to be able to do.
Make sure the disconect is pulled and with you while checking so no one turns it on while you're in there. But if the short to ground is bad enough to trip the breaker there's probably nothing you're going to be able to do.
#3
03-06-05, 07:39 AM
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Sounds like the compressor crankcase heater wires.
When they blow some of them blow apart and the wire pulls apart from the heater so when you check it and pull on the wires they don't show a reading to ground.
There should be a black ribbed wire that connects to the bottom of the contactor and connects to a purple wire with a white wire nut.
This is the heater wire the purple wire is the heater thermostat wire.
Check the wire schematic.
When they blow some of them blow apart and the wire pulls apart from the heater so when you check it and pull on the wires they don't show a reading to ground.
There should be a black ribbed wire that connects to the bottom of the contactor and connects to a purple wire with a white wire nut.
This is the heater wire the purple wire is the heater thermostat wire.
Check the wire schematic.
#4
03-07-05, 06:32 PM
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Thanks for the replys guys.
ScottG, you hit it right on the head. I actually stopped troubleshooting as soon as I realized it was somewhere near the compressor. I kind of figured that it might be the heater thinking that it's the only component in there that needs constant 120v. But I wasnt going to go any further because my knowledge consists of Petrochemical / refining / Power instrumentation and controls. While the comcepts are the same, I havent fooled around with HVAC as of yet.
I called a service tech (work covered under home warranty) and he came out and diagnosed it as the heater.
I think it might have been caused by moisture. The bottom of the unit was clogged up with leaves and such so the water couldnt drain. The heater wires were basically sitting in water.
I didnt have a schematic onme...but I was trying to figure out how the heater could have caused the direct short between both poles and not to ground?
Thanks again fellas!
ScottG, you hit it right on the head. I actually stopped troubleshooting as soon as I realized it was somewhere near the compressor. I kind of figured that it might be the heater thinking that it's the only component in there that needs constant 120v. But I wasnt going to go any further because my knowledge consists of Petrochemical / refining / Power instrumentation and controls. While the comcepts are the same, I havent fooled around with HVAC as of yet.
I called a service tech (work covered under home warranty) and he came out and diagnosed it as the heater.
I think it might have been caused by moisture. The bottom of the unit was clogged up with leaves and such so the water couldnt drain. The heater wires were basically sitting in water.
I didnt have a schematic onme...but I was trying to figure out how the heater could have caused the direct short between both poles and not to ground?
Thanks again fellas!
