neutral of a branch circuit be reduced in size

[wyboy]

We have a 54 KW boiler, 240 single phase that is continuous duty which is 281 amps. Will feed with (2) 300 KCMILL conductors on 300 amp OCPD. There is a small neutral load of less than 3 amps. Can the neutral of a branch circuit be reduced in size from the phase conductors. If so where is it in the NEC?

 

[augie47]

Is there an OCP device at the furnace making this circuit a feeder or is it actually the branch circuit to the furnace ?

 

[Dennis Alwon]

If is is a feeder then yes but the neutral cannot be smaller than the required equipment grounding conductor. If it is a branch circuit then IMO, you cannot. So run a feeder to the equipment and use a disconnect with overcurrent protective device and then you are good to go

 

[don_resqcapt19]

If is is a feeder then yes but the neutral cannot be smaller than the required equipment grounding conductor. If it is a branch circuit then IMO, you cannot. So run a feeder to the equipment and use a disconnect with overcurrent protective device and then you are good to go

What says that the grounded and ungrounded conductors for a branch circuit must be the same size?

 

[augie47]

What says that the grounded and ungrounded conductors for a branch circuit must be the same size?

Interesting..
I was heading the same direction as Dennis (I think) in that Feeders (and services) give the allowance for neutral reduction but I fond no such wording in Art 210.
It appears in the OPs situation, 210.19 would allow a #14.

 

[roger]

The problem with a reduced neutral in a two wire branch circuit is 240.4, particularly 240.4(D), the smallest conductor in the circuit will govern the size of the circuit and the OCPD.

Roger