Disconnects or breakers or both for Air Conditioners.

[Nomad776]

I’m working on a job where the drawings show the electric heat and AC condensers are protected by only the breaker and a non fused disconnects. Is this permissible? Don’t they have to have properly sized fusible disconnects too? Can anyone clarify? This is a restaurant BTW.

 

[electrofelon]

I’m working on a job where the drawings show the electric heat and AC condensers are protected by only the breaker and a non fused disconnects. Is this permissible? Don’t they have to have properly sized fusible disconnects too? Can anyone clarify? This is a restaurant BTW.

Generally no issue. I use them all the time. Possible issues with NF discos are:

1. Equipment specifically says fuses
2. Available fault current is higher than 10k.
3. The breaker exceeds the max for the machine (say maybe its a feeder tap or sone wierd situation where you don't want to change the breaker).

That's all I got.

 

[Nomad776]

Generally no issue. I use them all the time. Possible issues with NF discos are:

1. Equipment specifically says fuses
2. Available fault current is higher than 10k.
3. The breaker exceeds the max for the machine (say maybe its a feeder tap or sone wierd situation where you don't want to change the breaker).

That's all I got.

Thanks! One other question doesn’t the breaker have to be calculated at 115% of the name plate rating?

 

[Little Bill]

Thanks! One other question doesn’t the breaker have to be calculated at 115% of the name plate rating?

The nameplate already has the 125% factored in. MCA= Minimum Circuit Ampacity, that is what you size the wire from.
Max OCP (will say fuses if that is what they require) = Max breaker or fuse
So if it says "Max breaker size 40A, that is the max you can install. You can go smaller but you risk it tripping on start up.
In short, put in what the nameplate says!

 

[Nomad776]

The nameplate already has the 125% factored in. MCA= Minimum Circuit Ampacity, that is what you size the wire from.
Max OCP (will say fuses if that is what they require) = Max breaker or fuse
So if it says "Max breaker size 40A, that is the max you can install. You can go smaller but you risk it tripping on start up.
In short, put in what the nameplate says!

Thanks for your help gentleman!

 

[Strathead]

The one thing to be careful of. Many higher AIC breakers are not made in some "standard" sizes, especially 35 amps and 45 amps. If you don't know the size or the AC guy changes the unit and it becomes one of these MOCP's you may be stuck adding a fused disconnect. If that cost is going to be born by you then you need to make the decision.