HMCP used as a feeder, but thermal magnetic down stream

[adamscb]

Forum,

I have 480v single-phasing coming into a 480/120v transformer that goes to a 120v/240v panel. If the panel has a 200A main circuit breaker (thermal magnetic), can I use an HMCP on the primary side of the transformer?

(Transformer is 50kVA).

 

[Jraef]

No. There is no valid use for an HMCP (aka Mag Only, or officially, IT (Instantaneous Trip only) breaker) other than part of a LISTED FACTORY ASSEMLED COMBINATION STARTER. None.

 

[petersonra]

Forum,

I have 480v single-phasing coming into a 480/120v transformer that goes to a 120v/240v panel. If the panel has a 200A main circuit breaker (thermal magnetic), can I use an HMCP on the primary side of the transformer?

(Transformer is 50kVA).

you can, but it won't meet code unless you put a real CB or fuses in as well.