Fuses

[AdamS]

Does a code violation exist here in regards to fuse size?

I have an AC disconnect that is being used as a disconnecting means for an Inverter. The inverter is being fed from a 2 pole 20a breaker 220v. The inverter doesn't require a fused disconnect, a non fused would have been suffice. Our shop sent out the fused disco along with 2 30a fuses and expects us to use them. Is there a violation?

 

[augie47]

If the breaker is providing the proper protection for the equipment and the conductors then
the disconnect, fusible or not, is just that... a disconnect. The fact that the fuse is larger is not relevant.

 

[AdamS]

If the breaker is providing the proper protection for the equipment and the conductors then
the disconnect, fusible or not, is just that... a disconnect. The fact that the fuse is larger is not relevant.

My thought was, since another form of over current protection was added to the circuit (fuses) they should be sized accordingly. I couldn't find anything other than 690.10 B (2011 code) which states that the conductors have to be protected from overcurrent in accordance with article 240. I guess the circuit breaker covers that.

 

[ActionDave]

My thought was, since another form of over current protection was added to the circuit (fuses) they should be sized accordingly. I couldn't find anything other than 690.10 B (2011 code) which states that the conductors have to be protected from overcurrent in accordance with article 240. I guess the circuit breaker covers that.

I agree it is a non standard set up but it meets the code and is in no way dangerous. No worse than feeding a 100A main breaker panel from a 50A breaker.

 

[ron]

I do this all the time (oversize local disconnect fuses), when I need a higher short circuit rating for the disconnect and I don't want the local fuses to blow, and rely on an upstream properly sized circuit breaker.