I'm running a line to an outbuilding where the main use will be as a 48A vehicle charger. At most 2 120v circuits, one 20A and one 15A lighting. If I have #2 conductors, will a #2 neutral be adequate? Seems like not much should be flowing in the neutral for the 48A 24v charging circuit?
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1Believe you have to go with the 48amp size to the building at minimum, but you can use larger aluminum wire which is much cheaper than copper. It is not what is planned for right now, but what might happen in the future or an oops.– crip659Commented Aug 1, 2022 at 16:43
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Most inspectors require a feeder like this to have the same size neutral as the hots. There are cases where the neutrals are much smaller but usually on 3 phase where a transformer is pulling only a small portion of the total load or 277v lighting on a 480 panel, other than this I can only think of dryers and cooking equipment I don’t remember any other exceptions.– Ed BealCommented Aug 1, 2022 at 17:36
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1Agreed, the place to scrimp on heavy feeder is by using aluminum wire, not by shaving neutrals. 2 AWG aluminum is good for 90A which will support dual "60A" (48A) EVSEs using Share2 power sharing tech (a must-know if you foresee two EVs), + other loads.– Harper - Reinstate MonicaCommented Aug 1, 2022 at 17:37
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Sorry, but the neutral must be the same size as the hots. Ground wires can be down sized, but not the neutral. You'll be installing a sub-panel for the breakers (EV charging, 120v outlets and 120v lighting)
answered Aug 1, 2022 at 16:46
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2George is correct about the only place you will see a reduced size neutral residential is on ovens @70% if memory serves but table 259.102.c.1 can provide a size– Ed BealCommented Aug 1, 2022 at 17:22
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Not sure I understand the comment about downsizing ground wires. There isn't a ground wire going to the outbuilding; there's a ground rod/connection at the outbuilding, right? Commented Aug 1, 2022 at 20:03
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1@GaryAitken Under US NEC for many decades now, a ground wire (or metallic conduit serving as one) AND ground rod(s) at the outbuilding are BOTH required. So your service to the building needs to be 3 wires in metallic conduit or 4 wires, and the ground and neutral must be isolated at the subpanel in the outbuilding.– EcnerwalCommented Aug 1, 2022 at 20:13
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@GaryAitken the comment about downsizing a ground wire was just a general comment, not necessarily specific to your situation. There is tons of information here on SE on sub-panels. Take a peek and you'll learn everything you need to know. Commented Aug 2, 2022 at 18:43