Max Circuit Breaker
Last Post 04 Nov 2014 10:46 PM by arkie6. 11 Replies.
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YonderUser is Offline
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03 Nov 2014 08:34 PM
Hello, I recently had a Water Furnace Series 5 038 installed. The manual states that the maximum sized circuit breaker it should be installed on should be 40 amps, but my installer put it on a 50 amp breaker. Is that fine, or is that 40 amp maximum an important direction that shouldn't be ignored? Thanks for your time.
arkie6User is Offline
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03 Nov 2014 11:01 PM
What size wire was installed between the circuit breaker and heatpump?
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04 Nov 2014 01:58 AM
Both the main unit (the 50 amp breaker that maybe should be 40 amps) and the auxiliary heater (60 amp breaker as the manual specifies) are 6 gauge hot/neutral and 10 gauge ground.

Those are both 240V double rail breakers obviously.

Thanks for the reply!
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04 Nov 2014 07:50 AM
The installer probably ran #6 AWG to the heatpump because he had it on hand for the electric aux heat strips. Or maybe your wiring run is very long (>100' ?) and he was trying to limit voltage drop at the compressor. #8 AWG would have been sufficient for the electrical load on a 3 ton heatpump and auxiliaries such as loop pump and hot water generator pump unless you have a very long run of wire. It is possible that the larger #6 AWG wire may not fit in the terminals of the 40A circuit breaker is why he went with the 50A breaker. The electric code focuses on the fact that circuit breakers are sized to protect the wiring; however, in your case, an electrical fault inside the heat pump may result in more damage than would occur with a 40A breaker. If it was me, I would try to get a 40A breaker installed assuming the wire terminals are large enough to accommodate #6 AWG; otherwise, I would probably just leave it as is.
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04 Nov 2014 07:55 AM
Ok, thanks very much Arkie.
ChrisJUser is Offline
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04 Nov 2014 08:03 AM
My electrician was able to get the #6 into a 40 amp breaker, but not a 30 amp, which is what my 5000 watt aux called for.

Chris
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04 Nov 2014 09:17 AM
The installer is the one who will make warranty claims so while technically this is improper and could be grounds to void warranty, who's gonna tell?
Joe Hardin
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04 Nov 2014 10:50 AM
In theory, 50A into a motor that is supposed to be protected at 40A could cause a fire or meltdown. I'd put in a 40A breaker and if necessary, trim down the end of the wire to fit. Legal? I have no idea.
Bill NeukranzUser is Offline
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04 Nov 2014 11:36 AM
Posted By arkie6 on 04 Nov 2014 07:50 AM
The installer probably ran #6 AWG to the heatpump because he had it on hand for the electric aux heat strips. Or maybe your wiring run is very long (>100' ?) and he was trying to limit voltage drop at the compressor. #8 AWG would have been sufficient for the electrical load on a 3 ton heatpump and auxiliaries such as loop pump and hot water generator pump unless you have a very long run of wire. It is possible that the larger #6 AWG wire may not fit in the terminals of the 40A circuit breaker is why he went with the 50A breaker. The electric code focuses on the fact that circuit breakers are sized to protect the wiring; however, in your case, an electrical fault inside the heat pump may result in more damage than would occur with a 40A breaker. If it was me, I would try to get a 40A breaker installed assuming the wire terminals are large enough to accommodate #6 AWG; otherwise, I would probably just leave it as is.

This is a very good response.

I would recommend one change: if the recommended max circuit breaker size, as specified by the heat pump manufacturer, is 40 A, then this is what must be in place.  You otherwise have at minimum a warranty violation, and maybe a (slight) potential fire hazard at the heat pump unit.

Interestingly, manufacturers (it's really the distributors who the warranty is with) will check that the proper circuit breaker was in existence at the time of certain claimed warranty failures (i.e. some WaterFurnace distributors do this).  And they will deny coverage if installation was not to the manufacturers specifications.

Best regards,

Bill


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arkie6User is Offline
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04 Nov 2014 03:38 PM
The compressor should have internal thermal overload protection to prevent an overload condition from burning up the motor. The compressor nameplate should state "Thermally Protected" if this is the case. The circuit breaker provides ground fault or instantaneous overcurrent (IOC) protection for the wiring, and to a lesser extent the compressor. Since the compressor motor is hermetically sealed within the metal compresser housing, the only real area of concern with a ground fault in the compressor is the manufacturer's wiring from the terminal strip where the field wiring lays down in the cabinet to the compressor motor. This wire is likely much smaller than #6 AWG, probably only #10 AWG for a 3 ton compressor. Smaller wiring feeding loop pumps and other auxiliaries fed from the heat pump should have individual fuses/circuit breakers protecting this smaller wiring. The best option would be to replace the 50A breaker with a 40A breaker; however, if the #6 AWG wire won't fit the terminals of your particular 40A breaker,  you can't just trim wire strands to make it fit and maintain the UL listing of the device which is an electrical code requirement.

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04 Nov 2014 04:44 PM
Cutting the wire down would give any inspector fits, it is a completely uncontrolled modification, you have no idea if remaining strands are nicked, as well as not knowing how many strands made it into the connection. The right way is to just splice on a wire stub of the correct size. The splices are a bit clunky, but they get the job done. Just make sure to leave the splices inside the panel.
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04 Nov 2014 10:46 PM
I was in Lowes this evening and wandered down the electrical equipment isle. A Square D QO series 40A breaker would easily accept #6 AWG, but a Square D Homeline series 40A breaker would only accept up to #8 AWG per the markings on the breaker. The QO breaker had much more robust wiring terminals than the Homeline breaker. The QO series breaker also costs ~twice as much as the Homeline breaker and the QO and Homeline breakers are not interchangeable (different width breakers). Also, an EATON CH series 40A breaker would accept #6 AWG. The EATON CH series breaker is comparable to the Square D QO series in quality and cost. So, the type of breaker panel and breakers you have will determine whether or not #6 AWG wire can be used with a 40A circuit breaker.
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