equipment protection

[Mike01]

If the manufacturer only list OCPD sizing requirements for packaged mechanical equipment for fuse sizing can a c.b. be used instead of the fuse?

 

[Dennis Alwon]

If the manufacturer only list OCPD sizing requirements for packaged mechanical equipment for fuse sizing can a c.b. be used instead of the fuse?

If the unit states max ocpd to be fuses than you must install fuses to comply. A simple fused disco will take care of this to make it compliant.

 

[don_resqcapt19]

Yes, where the equipment instructions or nameplate do not specify the type or OCPD required you can use either a breaker or a fuse.

 

[Mike01]

just curious

just curious

but where in the code does it state this? "If the unit states max ocpd to be fuses than you must install fuses to comply" I know a fused disc. sw. would accomplish this but still curious where this is derived from?

 

[qcroanoke]

but where in the code does it state this? "If the unit states max ocpd to be fuses than you must install fuses to comply" I know a fused disc. sw. would accomplish this but still curious where this is derived from?

2008 NEC
110.3 (B)
So if it says fuses you must use fuses.

 

[augie47]

Code-wise, derived mostly from 110.3(B), manufacturer instructions.
It normally indicates that when the equipment was listed, it was only tested with fuse protection. (My understanding is that the more testing, the more the cost of the test)

 

[Jraef]

Code-wise, derived mostly from 110.3(B), manufacturer instructions.
It normally indicates that when the equipment was listed, it was only tested with fuse protection. (My understanding is that the more testing, the more the cost of the test)

This is correct. Generally, fuses, especially current limiting types, allow a higher level of series protection for equipment, especially with the new SCCR requirements. They therefore need less expensive testing than circuit breakers do. To test with circuit breakers, UL typically requires a destructive test, whereas with fuses they often allow a calculated evaluation.