neutral of a branch circuit be reduced in size

wyboy

Senior Member
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

Moderator
Staff member
Location
Tennessee
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

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
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

Moderator
Staff member
Location
Illinois
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

Moderator
Staff member
Location
Tennessee
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

Moderator
Staff member
Location
Fl
Occupation
Electrician
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
 
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