Condensor went, HVAC guy is blaming electrician, is this possible?

Question

My brand new HVAC unit, the condensor died. The unit has a sticker that says the following:

Minimum Circuit Ampacity 32 amps
Max Fuse / Breaker 50

The electrician ran a 8 gauge wire with a 40 amp breaker to the ac. The HVAC guy is telling me it should have been a 50 amp circuit with a 6 gauge wire.

The HVAC guy has replaced the condensor, the electrician has replaced the 40 amp breaker with a 50 amp, but did not run a 6 gauge line.

The HVAC guy wants $750 for his work on replacing the condensor on the brand new unit he installed.

So I guess my questions are:

1. Is this even possible for the condensor to burn out due to the lack of electric to it?

2. Was the electrician clearly at fault, or should the unit have worked on a 40AMP breaker?

3. Is the HVAC guy at any fault for not checking the electrical runs before installing the unit?

4. Is the run of 50amp breaker on a 8 gauge wire safe/sufficient/proper?

I'm in the middle of a finger pointing game and I am the one get stuck with the bills here. Thanks for any help!

Answer 1

Per the National Electric Code (assuming you are in the US), #8 is for up to 40A, the Minimum Circuit Ampacity (MCA) was 32A, so there was no issue with the wire size he initially selected. The MCA rating is based on the 125% factors already, so you do NOT need to do them again if you already have that number available to you on the nameplate.

Bottom line, the HVAC guy is just trying to dodge responsibility for a defective product.

Also, a "buzzing" sound would not be coming from the breaker unless it was loose. That sound was likely the result of a failed starting capacitor.

Answer 2

Wire and breakers are current-limiting. That means that the wire heats up and eventually fails (burns) if the load (your condensor) draws too much current, or your breaker trips when it senses too much current flow, assuming the breaker is functional.

A device draws whatever current it requires for a given input voltage. If the breaker never tripped and the wire never failed, then the condensor was almost certainly faulty, since there is no mechanism by which the wire or breaker could contribute more current to the fault. Current generates heat, and heat destroys electrical things.

The condensor was either faulty out of the factory or mishandled/miswired in such a way that it failed after installation but without drawing enough current to trip the breaker or melt your wiring.

All fingers should be pointing at a faulty condensor.

Answer 3

The sticker on the condensing unit stated MAXIMUM 50-A breaker. A 40-A breaker satisfies this requirement, but it seems to me that the electrician should have installed a 50-A breaker, if the #8 wire on this compressor allows that. The sticker on my 27-year-old Carrier 42000 kBTU/h R-22 condensing unit (3.5 ton) states MAX HACR CKT-BKR 40 and the breaker is a 40-A.

Did the HVAC tech know there was a 40-A breaker on the circuit and proceed with the hookup despite reservations? It seems to me that the HVAC tech cannot reasonably claim the electric service is at fault.