Fusible or Non-Fusible

[Jody Boehs]

At my plant, we will be installing a glycol chiller. I will be running a 100 Amp service to it. This service will be protected with a 100 Amp circuit breaker. The distance between the chiller and the distribution panel is approximately 110' - 130' depending on how the conduit will be installed.

Do I need a Fusible or Non-Fusible Disconnect next to the chiller unit?

 

[infinity]

Since the circuit already has an OCPD at its origin in the DP you will not need another one at the disconnect switch so a non-fused will work. Just for clarity since your feeding this from a distribution panel you are not running a service. In electrical speak that has a distinct and different meaning.

 

[Jody Boehs]

Since the circuit already has an OCPD at its origin in the DP you will not need another one at the disconnect switch so a non-fused will work. Just for clarity since your feeding this from a distribution panel you are not running a service. In electrical speak that has a distinct and different meaning.

Thank you for the clarification. I get those terms mixed up sometime. Would it be a 'branch circuit'?

 

[tom baker]

Yes since its supplying one device. If you have a fused disconnect then it becomes a feeder. A service has a lot of other requirements, you would have a service to your plant from a utility
A non fused disconnect also works for LOTO.

 

[Jody Boehs]

Thank You!

 

[electrofelon]

There is a chance that the chiller would need or spec fuses only or a certain fuse for SCCR or AIC purposes. Probably not very likely these days, but a possibility.

 

[GoldDigger]

And if the available short circuit current at the chiller location is high enough, you may need to spec a fused disconnect to get a high enough SCCR.
Even if there is sufficiently rated OCPD upstream it may not series rate with your local disconnect.

 

[Eddie702]

@Jody Boehs

I would suggest checking the chiller nameplate. It will show MCA (min. circuit amps) to size the conductors and MOCP (max over current protection)

I have seen chillers that require fuses for protection instead of circuit breakers as @electrofelon mentioned. Not that common but it happens. The chiller may also have a disconnect on it (depends how it was ordered)

 

[Jraef]

And if the available short circuit current at the chiller location is high enough, you may need to spec a fused disconnect to get a high enough SCCR.
Even if there is sufficiently rated OCPD upstream it may not series rate with your local disconnect.

Absolutely.
Most Non-fused disconnects carry only a 10kA SCCR, so if you have more than 10kA at the terminals, you cannot connect it. When you add the fuses, the SCCR then generally have the same SCCR as the fuse interrpt rating, i.e. 100kA or more. The fuses don't actually need to be IN the disconnect though, just in the circuit with the disconnect.

It's rare, but if you have an NF disconnect that is series listed WITH the circuit breaker in the panel at a higher SCCR, then that's acceptable. But the few I have seen require that they are the exact same brand AND on a documented series listed combination tech data sheet. For example I believe that some Square D NF disconnects are series listed with specific Sq. D breakers.

 

[jim dungar]

... have the same SCCR as the fuse interrpt rating, i.e. 100kA or more. The fuses don't actually need to be IN the disconnect though, just in the circuit with the disconnect.

Usually rejection style fuse clips must also be installed.