On an inspection yesterday on a home built in 2004, the label on the air handler indicated that it needed a minimum ampacity of 59 amps. The circuit breaker for the air handler was rated at 45 amps. To make matters worse, the wire connected to the circuit breaker was a 10 gauge wire which,as I understand it, is only rated for 30 amps.
First of all, how was this unit operating without tripping the breaker? Second of all, am I right that the wire is undersized?
The OCPD is sized from the MCA up to the maximum listed on the nameplate. The conductors are sized by the MCA listed on the nameplate. Since that nameplate is for multiple units are you sure that the one indicated is correct? Was this unit ever used for heating as well as A/C?
When this label is used on the air handler the a/c contractor has to mark which part of the label applies. I can’t say that all of them do it, but most of the inspectors in that county would not pass the electrical inspection if it was not marked. For that reason, I am assuming that it is marked correctly.
As to heating, the home is 9 years old so I would again assume that the heater has been used. The heat pump would take care of most of it but at some point, the aux strips would most likely have kicked in.
As to the wire, I often see a wire that is larger than the rating of the breaker on air conditioners because the electrician will estimate what he thinks it will need and will later find that he does not need the full capacity of the wire. In this case, the wire is smaller than the breaker.
Are you sure you were looking at the right circuit? I see a 60 amp just above the 45 amp in your photo. If there was no hot tub or remote distribution panel, that is likely the furnace circuit.
If you were indeed looking at the furnace circuit and it is 45 amp, the configuration is incorrect. What did the 60 amp breaker go to?
The listing on the air handler is for the electric strips… not the heat pump. The heat pump rating will be shown on the condenser unit outside. It is likely rated for max 45 amps.
If the nameplate information is correct then you need a conductor with a minimum ampacity of 59 amps and a 60 amp OCPD. The heater portion is rated at 40 amps so conceivable it could run on a 45 amp breaker with #10 conductors.
Yes, I do understand that I was just trying to explain that in most cases, the circuit would be drawing less than the full rating.
As to the 60 amp breaker, I do not remember what it was for, I do know that the label on the cover of the panel indicated that the 45 amp breaker was for the air handler. I double checked it when I saw the discrepancy. but now you have me wondering if it was mislabeled.
That may be the case.
William, thank you for making me see the obvious. I went back to the home and sure enough the wire from the 60 amp breaker was going to the air handler. I should have though to check that while I was there.
I should not rely on panel labeling when I see something that does not make sense.
Looking for the forest but there are so many trees in the way… happens to all of us once in a while.
