Existing AC wiring feeder circuit

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smallfish

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A replacement Lennox brand AC unit and 60-amp fusible pullout disconnect with 45 amp fuses with copper # 8 THHN branch circuit wiring in a whip to the outside AC unit was installed. The feeder to this pullout disconnect is a SE cable with #8 Aluminum wire that runs indoors to the residential electrical panel and is protected by a two pole 50 amp breaker. This feeder and breaker appear to be original house wiring for the previous AC unit.

The AC unit nameplate requires a minimum circuit ampacity of 28 amps and a Maximum Fuse or Circuit Breaker Ampacity of 45 Amps.

Do you think that the wiring and/or overcurrent protection which was original and upstream of the 60-amp fusible pullout disconnect needs to be replaced?

If so what size wire and breaker is needed. Is it the homeowner's or contractor's responsibility?

The home is 20 or more years old.

Thanks.
 
smallfish said:
A replacement Lennox brand AC unit and 60-amp fusible pullout disconnect with 45 amp fuses with copper # 8 THHN branch circuit wiring in a whip to the outside AC unit was installed. The feeder to this pullout disconnect is a SE cable with #8 Aluminum wire that runs indoors to the residential electrical panel and is protected by a two pole 50 amp breaker. This feeder and breaker appear to be original house wiring for the previous AC unit.

The AC unit nameplate requires a minimum circuit ampacity of 28 amps and a Maximum Fuse or Circuit Breaker Ampacity of 45 Amps.

Do you think that the wiring and/or overcurrent protection which was original and upstream of the 60-amp fusible pullout disconnect needs to be replaced?

If so what size wire and breaker is needed. Is it the homeowner's or contractor's responsibility?

The home is 20 or more years old.

Thanks.
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what part do you think is in need of replacement.

none of the wiring is below the MCA of 28A and there is a 45A fuse on the circuit.
 
I was wondering if the original 50 amp circuit breaker was set too high to protect the original feeder SE cable with the aluminum #8 AWG wires.
Do these feeder wires need to be protected at their rated ampacity per TABLE 310.15(B)(16) or does Section 215.2 apply requiring the feeder to be capable of carrying the load?
 
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Taking into account that we don't know what the MCA & MOCP were on the original unit and at the time it was installed #8 AL SE probably had a 40 amp ampacity, it iks somewhat safe to assume the install met Code at the time.
A case could be made that the panel breaker be changed to a 45 since thats the max allowed by the unit and under todays Code the ampacity would be 40 at best.
 
I would question if you actually have a feeder. What if the 45 amp fuses are considered supplementary protection?
 
infinity said:
I would question if you actually have a feeder. What if the 45 amp fuses are considered supplementary protection?
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seemingly an age old "discussion". IMHO, when you read the definition of supplementary OCP, it's a stretch to call the OCP rated at MOCP "supplemental", but, hey!, whats one man's opinion.
 
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