Adjustable Trip Unit on LV Breaker - 400 Amp feeder to distribution panel

[drktmplr12]

Industrial site, locked electric room

800A frame switchgear breaker with 400 amp trip unit. we want to connect #4/0 and adjust the trip down to 250. I see 240.4.C allows adjustment below maximum long time pickup only with restricted access. I am being told that if we adjust down from 1.0, the breaker needs to be labeled that the conductors are not rated for the full capacity of the trip unit. Haven't heard of this before and can't find a code reference.

Has anyone experienced a similar requirement from AHJ or has a code reference to help?

Thanks

 

[jim dungar]

There is no such requirement in the NEC.
The trip unit adjustments do need provisions to be sealed, so it can be evident changes may have been made.

 

[augie47]

Jim:
What about 240.6(C)(3) ??

 

[jim dungar]

Jim:
What about 240.6(C)(3) ??

That is only one of three methods. The method I mentioned is allowed per 240.6(C)(1) and is usually the method provided by the breaker manufacturer as a standard offer on molded case style breakers listed under UL 489.

 

[augie47]

agree, but, for my learning, if it a locked room, accessible to only qulaified personnel, the sealed breaker adjustment would not be required, correct ?

 

[jim dungar]

agree, but, for my learning, if it a locked room, accessible to only qulaified personnel, the sealed breaker adjustment would not be required, correct ?

I have always taken it to mean locked equipment doors/compartments. like you find on old draw out breakers.

 

[augie47]

Likely you are correct but I wish the CMP had been more specific. The wording had me leaning toward a broader scope.

 

[drktmplr12]

(3) Locked doors accessible only to qualified personnel

I can certainly see an inspector being obtuse and insisting this means "equipment doors" not "electric room doors". In the strictest sense, a door is a door. But an A-H-J is G-O-D so not much you can say to argue because it is not specific. I personally like the seal method. Simple to implement. Can't argue it. Can't defeat it.

Thanks for the input, everyone!

 

[jim dungar]

Likely you are correct but I wish the CMP had been more specific. The wording had me leaning toward a broader scope.

It is almost a silly rule anyway. The NEC only requires a method for reducing the likelihood of a settings change be provided. It does not require the method to actually be implemented.