Service Disconnect Issue

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Old 12-11-18, 04:52 PM
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Service Disconnect Issue

I have a Trane heat pump that was installed in late 2015 and is under a 5 year, parts only warranty. It stopped working yesterday. No Tstat display, everything dead. I popped the Tstat off the wall to reset it, with no success. I have breakers for both the heat strips and the heat pump, so I reset them both (neither were tripped). No joy. I pulled the AC disconnect at the heat pump and replaced it again. No joy.

I then metered the heat pump and fount 240v on the live side of the main contactor. If I push the contactor, the heat pump starts. There is no 24V to the contactor coil.

I went upstairs to the air handler and found no low voltage there, although I did measure 120VAC on the relay.

I called the furnace folks, thinking I had reached the limit of my expertise. They came out and looked it over (I was not home at the time, my wife let them in) and advised me by phone that the control board in the air handler was bad, and it was under a Trane parts-only warranty. The labor would be $245, plus the $90 diagnostic fee.They did not have the board and would have to come back tomorrow.

I was a little frustrated by $335 for a bad board that was under warranty, so I called and told them I would pick up the board and install it myself, and to call me when they had it on hand. They were quite reluctant to do this, but agreed. Not wanting egg on my face, I decided to give the air handler a closer look.

From what I could tell, this control board was not getting any power. The 24V transformer coils were good, but the primary side had no power. It took me a while to figure out that this was fed by the heat strip breaker, which I know was fine. Then I realized that between the air handler and the breaker is a service disconnect, like the one on the heat pump. I pulled it and metered 240V. I then put it back in and everything started working. AC, heat, fan, everything.

My question is, do these service disconnects require periodic resetting, just to keep the contacts clean? We have never used the heat strips, so I don't expect they have every carried a lot of current. This is in an attic, so I wouldn't think moisture is an issue. I didn't see any arc pitting or any signs of high temperature.

Glad I didn't pick up the control board, as they would have likely given my a really hard time after discovering it didn't fix the problem. I called them back and advised them I didn't need the part. I also told him to come and pick up his Milwaukee cordless screwdriver he left behind. He sheepishly thanked me and told me they were waiving the diagnostic fee.

So what is the deal on these service disconnects. Should I get so dielectric grease for it? Should I yank and reset it once per season? It looks like this one: https://www.homedepot.com/p/GE-60-Am...0RCP/100674085
 
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  #2  
Old 12-11-18, 05:04 PM
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Welcome to the forums.

That disconnect inside an attic should not corrode and should not require any maintenance.
It sounds like it was never pushed in all the way and just worked loose.
 
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Old 12-12-18, 04:14 AM
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That is possible. The adjoining room has two treadmills that are used for running every morning. I'm kicking myself for not checking it when I reset the breakers. Thanks.
 
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Old 12-12-18, 06:37 PM
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Now Brown Knows. ....................................
 
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