Trane XL16i Blowing Circuit Breaker

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Old 05-18-19, 05:54 PM
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Trane XL16i Blowing Circuit Breaker

Hello All,

I have a Trane XL16i Heat Pump/AC unit, the second the contractor engages it blows the circuit breaker..

I called an HVAC tech out, they want to sell me a new $800 circuit board. But I know enough about circuit boards and electrical that 240v is NOT going threw that circuit board.

The wire on the capacitor between the capacitor and the contractor burned off.

I have replaced that wire.

I am thinking it has to be either a short in the capacitor, a short in the fan motor, or the compressor.. But I am unsure how to trouble shoot those items to find the problem.

Is anyone able to assist? I am very capable, just need some guidance.

Thanks in advance.

-ThaChad

 
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Old 05-18-19, 10:18 PM
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Ok..... you're capable. Do you have a meter and know how to use it ?
Your going to need an ohmmeter to check for shorts.

Doubtful it's the cap or the fan motor. My bet would be on the compressor.
Discharge the capacitor. Make sure the power is disconnected to the condenser.

Do a quick check. Set the meter to ohms Rx1 or auto for digital. Clip one meter lead to the metal frame. Touch each lead of the cap.... any reading ? If yes..... remove the wires from the cap. check each one separately. One will go to the fan, one to the compressor and one to the contactor. Which one has the short ? Leave that one disconnected. Reconnect the other two.

If it was the compressor wire....... you will need to locate the other two compressor wires and disconnect them. Remember to take pictures and/or ID where they go. Now check from all three to ground. There should be no measurement. If there is..... the compressor is shorted. This same test goes for the fan as it also has three wires.

Pictures of the contactor, cap and associated wiring are very helpful to us.
How-to-insert-pictures.
 
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Old 05-19-19, 08:12 AM
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Yeah, I have lots of meters! lol

Okay. So it didn’t have a short. However, I disconnected the power connector to the compressor and turned the unit on, everything fired right up. So I am assuming that the compressor is froze up.

It’s sad that the HVAC tech didn’t even do this troubleshooting.

The good news is that the compressor has a 12 year warranty and is still in warranty until 11/2021.

The bad is that I need to have the same HVAC company that couldn’t even diagnose the problem fix it!

Thank you for the help!

-ThaChad
 
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Old 05-19-19, 08:25 AM
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If you want to go a step further you can check between the individual compressor lines to check the motor windings.

A defective capacitor could also cause a start up problem but it doesn't usually cause the breaker to trip as soon as the contactor is engaged.
 
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Old 05-19-19, 08:51 AM
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I did test the capacitor. It’s not shorted. It charges up and discharges.

-ThaChad
 
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Old 05-19-19, 09:07 AM
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Compressor replacement is not taken lightly. The tech will need to come in and measure the actual resistances on all three wires to determine if there is a winding short. If the windings measured ok then a current probe is used to confirm draw on start and run windings.

Just a thought here..... do you have another breaker in the panel of the same size you can try ?
I don't think it's a defective breaker but it is a plus to rule it out.
 
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Old 05-19-19, 10:52 AM
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The first HVAC tech thought it was a defective breaker. So we replaced the service disconnect breaker outside by the unit.

-ThaChad
 
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Old 05-19-19, 11:18 AM
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Was that the one that was tripping ?
Typically there is only a disconnect at the unit or a circuit breaker type switch.
 
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Old 05-19-19, 02:29 PM
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At the unit there is a 50A service disconnect, which looks identical to a regular SquareD QO 50A breaker.. That is what we replaced.

Then there is a 30A breaker in the panel. They have both tripped. But the one in the panel typically trips. If the unit is “on” when I flip the breaker, It typically trips the breaker in the panel, if the unit is “off” when I reset the breaker and I turn it “on” with the breaker reset, it’s a toss up which one trips, sometimes they both trip.
-Masta
 
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