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Old 12-17-2011, 12:18 PM   #1
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Should 60A cutoff boxes for electric coil backup be warm to touch?


Hi.
Just set up an agreement yesterday to get a new heat pump system next week. But what are the odds of the current one suddenly acting up today:
I have a 21kW electric backup to a 1990s Carrier heat pump. It uses two separate 60A circuits to power it. Each of these 60A circuits has cables that come from separate cutoff boxes.
This morning the house was cool. Upon inspection, I saw one of the 60A breakers tripped, so I reset it. 10 minutes later, it tripped again.
I measured resistance on each of 5 electric backup coils, 10.7-11.1ohms each (no noticeable difference, so assuming no short for now).
So to see if one of the breakers was weak, I swapped the 4 wires that are powered by each breaker (8 wires total) and go to the the air handler and electric coil pack from each breaker to see if it was a weak breaker.
So far, the electric backup has run for an hour without tripping. So I would normally feel comfortable at this point thinking one breaker is weaker than the other, and maybe there's a weak short on one of the coils.
However, I noticed the two disconnect boxes are warm to the touch (maybe 100 deg F). Is this normal after the coils have been running for an hour?
Thanks,
Randy

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Old 12-17-2011, 12:24 PM   #2
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Should 60A cutoff boxes for electric coil backup be warm to touch?


should be. wire has a resistance and that creates some heat. that is why they have to size conduit for the number of wires it carries and voltage and load.

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Old 12-17-2011, 02:18 PM   #3
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Should 60A cutoff boxes for electric coil backup be warm to touch?


check the tightness of the wires into the box and going out the heat is coming from someplace....if yyou see any bubbled insulation just below the slip wire copper thats the heat
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Old 12-18-2011, 07:52 AM   #4
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Should 60A cutoff boxes for electric coil backup be warm to touch?


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Originally Posted by biggles View Post
check the tightness of the wires into the box and going out the heat is coming from someplace....if yyou see any bubbled insulation just below the slip wire copper thats the heat
Thanks to both of you on the feedback. I'm more at peace now... and warmer.
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Old 12-18-2011, 07:58 AM   #5
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Should 60A cutoff boxes for electric coil backup be warm to touch?


loose connections and the actual loads...comps and such can trip any breaker.so if the unit is starting too hard start the breaker is doing its job..like your starter in your car taking the hit when you go to start it
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