RATING OF DISCONNECT 60A FOR FEEDER

[al]

What is the rating of a 6/12 MLO panel relative to 225.39(D) requiring 60A minimum? Is it the main bus size, or the sum of all the installed breakers? Grey area?

 

[busman]

Re: RATING OF DISCONNECT 60A FOR FEEDER

Since this is a feeder, it has an OCPD at its origin. The rating of the feeder is the size of this OCPD.

Mark

 

[russ]

Re: RATING OF DISCONNECT 60A FOR FEEDER

You can only put a load on the panel, that the panel is rated for.
The sum of the breakers has nothing to do with the load calculation.
The load calculation according to article 220 will determine the feeder and overcurrent size, with 60 amp being the minimum

 

[iwire]

Re: RATING OF DISCONNECT 60A FOR FEEDER

Originally posted by busman:
Since this is a feeder, it has an OCPD at its origin. The rating of the feeder is the size of this OCPD.

Mark

Mark it has nothing to do with the size of the OCPD.

You could put in a 60 amp fused switch with 15 amp fuses.

It only applies to the rating of the disconnecting means, which can also be the OCPD but does not have to be.

 

[iwire]

Re: RATING OF DISCONNECT 60A FOR FEEDER

Originally posted by russ:
The load calculation according to article 220 will determine the feeder and overcurrent size, with 60 amp being the minimum

Russ the feeder and OCPD could be 15 amps only the size of the disconnecting means is mandated by 225.39(D).

225.39 Rating of Disconnect.
The feeder or branch-circuit disconnecting means shall have a rating of not less than the load to be carried, determined in accordance with Article 220. In no case shall the rating be lower than specified in 225.39(A), (B), (C), or (D).

 

[busman]

Re: RATING OF DISCONNECT 60A FOR FEEDER

Iwire,

I think you are right in interpreting the code. I wonder then, why have this requirement. It seems to achieve nothing since any disconnect would have to be sufficient for the rating of the circuit. I can see no logic to requiring an oversized disconnect.

Maybe one of our CMP guru's knows why this is?

Thanks,

Mark

 

[russ]

Re: RATING OF DISCONNECT 60A FOR FEEDER

Bob:

I think the wording is confusing,but I take it to mean the minimum overcurrent devise to be 60amp.

I guess if you want to install a 60amp disconnect and 60 amp wire, going to a panel, it would be OK to fuse it smaller, but I don't see the point.

This brings up a problem with 225.39(C)
If the rating, does not include the actual size of the fuse, you could put any size smaller than 100amp main in a dwelling.

In any case I would still hold out for the feeder size to the code implied minimums

 

[steve66]

Re: RATING OF DISCONNECT 60A FOR FEEDER

Russ;

You posted:

If the rating, does not include the actual size of the fuse, you could put any size smaller than 100amp main in a dwelling

This wouldn't work for a service though. Only a feeder. And not a feeder that carries the entire service. See 215.2(A)(3).

Steve