Thermostat/compressor wiring problems

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Old 07-07-16, 05:48 PM
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Thermostat/compressor wiring problems

I have an ecobee3. It has been set up for approximately 4 months and working fine. I have the R, G, W, Y, and C wires. The other day, the outside unit stopped turning on. The inside unit turned on fine.

I had an HVAC repairman come out and he said the wiring going from the Air Handler to the outside condenser unit was burnt and shorting out. They said this is likely caused by the ecobee as they have seen several instances just like this.

Could the ecobee even do something like this? I had my yearly inspection and the repairman said there was pitting on the contactor on the compressor. Could pitting cause the wires to get hot?

Is it a better idea to replace a contactor with pitting or will it work just the same?
 
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Old 07-07-16, 06:47 PM
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It's a better idea to find a new technician.

The thermostat has ABSOLUTELY nothing to do with the wiring burning or shorting out. The thermostat either supplies 24vac to the wire or it doesn't. An Ecobee stat doesn't work any differently than any other stat in that regard.

It's very likely the wiring to the condensor was nicked or exposed from the weather and touching metal. A defective contactor could also cause the problem.

Pitting on the contactor is a normal occurrence. If the contacts look excessively black then change the contactor. It's a relatively inexpensive part.

Most A/C systems are fuse protected and are limited in current in the control wiring. Usually a fuse would blow out or the transformer would burn up long before the wire did.
 
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Old 07-08-16, 05:28 AM
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Thanks for the response! I agree with you about the technician. I am convinced it's not the ecobee, either. It's possible, based on the location of where they "repaired" the wire, that it could have been weather exposure or a nick in the wire by something.

Could the contactor cause the wire to get hot if it was going bad? I may just replace the contactor to be on the safe side. I found a replacement one for $20.

I believe they did say there was a blown fuse. I wasn't there so I got this info 2nd hand.
 
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Old 07-08-16, 03:34 PM
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It's very likely the wire was damaged outside. It happens all the time from animals, weed wackers and weather.

A contactor with a shorted coil could cause a short but the 24v control system hardly delivers enough current to cause wires to burn.
 
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Old 07-11-16, 05:54 AM
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Just had another thought. Is it possible that the shorted wire at the compressor caused the ecobee to stop working? Or would the ecobee have some sort of protection in it for cases like this?
 
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Old 07-11-16, 03:34 PM
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In your opening post you said the inside air was blowing. Is that correct and if it is.... the stat should be ok.

This is sort of ongoing.... what is the problem currently with the system ?
 
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Old 07-11-16, 04:49 PM
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The inside air was blowing but the outside compressor wouldn't come on. Ecobee had me test the thermostat by wiring the compressor output to the fan and then the fan didn't come on. That confirmed that the ecobee wasn't turning on the compressor. I currently have a Nest hooked up while I work through the RMA with ecobee.
 
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Old 07-11-16, 07:44 PM
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Ahhhh.....ok. That explains it better.

In that case it appears that your air handler may not have a fuse and may have damaged the Ecobee. A short on the Y (compressor) line appears to have been the culprit.

I don't know much about those stats as I only use Honeywell products and they use relays for the devices. The Ecobee may not.

I would recommend installing a 3A fuse on the R line at the air handler. This fuse will protect all your stat, stat wiring as well as the transformer.
 
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Old 07-12-16, 06:00 AM
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There is a 5A fuse on the control board inside the AHU. I believe the tech said the fuse had blown and he replaced it.
 
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