Is it permissible by code to use an under sized neutral(#4)in a feeder for a mobile home? The reason I ask is because the supply house gave me #2246 feeder cable instead of the usual #2224 and I didn't notice it until the cable was pulled in to the conduit. Code reference please Thanks

Check out 220.22 of the 2002 NEC.

Chris

I am curious about the cable being used inside conduit. Is it listed to be used that way and does it have an insulated equipment grounding conductor? Thanks in advance.

Yes it is listed that way it is duel rated USE-2 RHH/RHW and the grounding conductor is insulated.Just want to know if a #4 neutral can be used and how to do the math to figure it out. Thanks

to figure your neutral load which tells you your wire size. see section 220.22