Compressor Disconnect Switch question

[Steevo]

I have a compressor location wired with 8/2+G from my load center, and have a 50A breaker installed currently to feed this circuit.

I may use a compressor that requires this much amperage, or I may not. Assuming I install a compressor that needs a 30A breaker, I'd downsize the breaker accordingly.

I want/need to have a disconnect switch at the compressor location, which is 40' from the load center, but not line-of-sight due to the bathroom poking out of that side wall.

I own a 100A single-phase fused disconnect switch that I'd like to utilize for the compressor disconnect, since I already have it. Given that the load center breaker will be sized properly for the compressor, is there any issue with the disconnect being fused at 100A?

 

[Aceman]

It's fine.

 

[sberry]

Some of the smaller comps can use a 50 anyway, the motor has its own thermal protection. Depends on the model.

 

[Norcal]

8 AWG NM (Romex) is only rated for 40A.

 

[Aceman]

8 AWG NM (Romex) is only rated for 40A.

I agree. Hopefully he was only upsizing the breaker for motor startup......?

 

[Steevo]

8 AWG NM (Romex) is only rated for 40A.

No problem. I do not see me putting in a 7HP compressor, more likely something around 5HP, so probably in the 30A start-up range.

I was just wondering if using the fused disconnect was going to be an issue.

I forgot to mention, but obviously I am talking a two-pole breaker and 230v motor.

 

[Norcal]

With proper overcurrent protection at the panel, as long as the lugs on the switch are rated to accept the 8 AWG, I see no issue w/ a 100A disco.

 

[Charles (in GA)]

What they are trying to say is that with the #8 wire, you should not have over a 40 amp breaker at the panel. The breaker is there to protect the wire, not the device at the end (compressor). The compressor most likely has a thermal overload in the motor that will shut it off if it gets too hot.

You should change the 50 amp breaker to a 40, to properly protect the #8 wire. As far as the disconnect, it doesn't even have to have fuses, it only needs to be a switch rated to carry at least the same amperage as the supply breaker. The 100 amp fuses are like having no fuse at all, and just a switch, so it is not an issue.

Charles

 

[Norcal]

What they are trying to say is that with the #8 wire, you should not have over a 40 amp breaker at the panel. The breaker is there to protect the wire, not the device at the end (compressor). The compressor most likely has a thermal overload in the motor that will shut it off if it gets too hot.

You should change the 50 amp breaker to a 40, to properly protect the #8 wire. As far as the disconnect, it doesn't even have to have fuses, it only needs to be a switch rated to carry at least the same amperage as the supply breaker. The 100 amp fuses are like having no fuse at all, and just a switch, so it is not an issue.

Charles

If the compressor motor is a 5 HP, & has overload protection, then the 50A is OK, in that case the circuit breaker is only there for short circuit protection.