Detached garage neutral sizing

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bclumen

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Elkridge, MD
Can the ungrounded conductor in a 240v 50a 4wire feeder to a detached garage sub panel be smaller than the current conductors?
215.2(A)(2) says it just can't be smaller than the EGC. This inspector couldnt find a code that prooves it has to be the same size as the current conductors and won't get back to me. Does anyone have one I can give him.

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There is only one lighting circuit and a circuit for the door opener.
I guess down the road the neutral load could be increased but do I have to plan for the unforeseen?
I respect the Authority and will replace if required to do so but I don't see where the NEC requires it

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bclumen said:
There is only one lighting circuit and a circuit for the door opener.
I guess down the road the neutral load could be increased but do I have to plan for the unforeseen?
I respect the Authority and will replace if required to do so but I don't see where the NEC requires it

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With a 50 amp feeder the EGC is #10.
Aren't we starting to split hairs here?

What size neutral conductor did you pull?

If the garage is detached and the feeder is in conduit then I'm guessing you may have pulled single conductor THWN or the like and could have been #8's for the ungrounded conductors. If the grounded conductor cannot be smaller than the EGC and with the EGC being a #10, how small are you wanting to go with the neutral conductor to the subpanel and why?

I generally pull a full size neutral on a feeder this small but that's just me.

JAP>
 
We installed two number 8 current carrying conductors a number 10 neutral and a number 10 EGC. The inspector is saying the neutral has to be the same size as the current carrying conductors but can't find a code reference requiring it.

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bclumen said:
We installed two number 8 current carrying conductors a number 10 neutral and a number 10 EGC. The inspector is saying the neutral has to be the same size as the current carrying conductors but can't find a code reference requiring it.

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If he cant find the code reference to defend it then you should be good to go. :thumbsup:

JAP>
 
bclumen said:
We installed two number 8 current carrying conductors a number 10 neutral and a number 10 EGC. The inspector is saying the neutral has to be the same size as the current carrying conductors but can't find a code reference requiring it.

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Sounds like you're good unless you ended up with a single 120 volt 50 amp load. :)
 
infinity said:
Sounds like you're good unless you ended up with a single 120 volt 50 amp load. :)
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jap said:
I don't know how you come up with this stuff. I'd of never thought of that. :lol:

JAP>
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Say one load in the garage were a 3000 watt 240 volt heater - there is 12.5 amps of load that will not utilize the neutral now you have a maximim possible neutral load of 37.5 before even looking at the balancing of 120 volt loads.
 
kwired said:
Say one load in the garage were a 3000 watt 240 volt heater - there is 12.5 amps of load that will not utilize the neutral now you have a maximim possible neutral load of 37.5 before even looking at the balancing of 120 volt loads.
Click to expand...

I think infinity was saying, if you have (1) 50 amp 120v load, then you've exceeded the #10 neutral size the OP has pulled in just (1) circuit, which is not normally the case but good thinking anyway.

JAP>
 
jap said:
I think infinity was saying, if you have (1) 50 amp 120v load, then you've exceeded the #10 neutral size the OP has pulled in just (1) circuit, which is not normally the case but good thinking anyway.

JAP>
Click to expand...

That was my point, although not likely it is possible to overload the reduced size #10 neutral.
 
Last edited:
Thanks. I agree, it is completely possible. But in this case, it helps knowing they have a 240V, 5KW hwh for an outdoor shower, 1 G.door opener and lights and plugs for 300 square ft. of seating area with one under cabinet fridge and ice maker.

So the inspector called me this am and approved the job.

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kwired said:
Say one load in the garage were a 3000 watt 240 volt heater - there is 12.5 amps of load that will not utilize the neutral now you have a maximim possible neutral load of 37.5 before even looking at the balancing of 120 volt loads.
Click to expand...

:?

If you have a 3000 watt 240v heater, and there is 12.5 amps of load on the 2 phase conductors and none on the neutral conductor, how did this take away from the max 50 amp load capability of the neutral at all?

JAP>
 
jap said:
:?

If you have a 3000 watt 240v heater, and there is 12.5 amps of load on the 2 phase conductors and none on the neutral conductor, how did this take away from the max 50 amp load capability of the neutral at all?

JAP>
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jap said:
If you pulled a full size neutral conductor that is.

JAP>
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you have 37.5 amps of capacity left over in the overcurrent protection/ungrounded conductors that is free to use for line to neutral loads.

May not actually be quite that simple but is the direction you go with that.

I ran a 600 amp feeder to a HVAC equipment room at a school building. All the HVAC equiment was three phase no neutrals. We did have some 120 volt lights and a general use 120 volt receptacle to supply in there as well - even with several empty spaces in the panel and consideration of possible future 120 volt loads -I figured with the 400+ amps of three phase load already being supplied there still would be no need for a feeder neutral larger then the minimum size EGC needed - there just wasn't that kind of capacity left on the feeder to add such loads.
 
kwired said:
you have 37.5 amps of capacity left over in the overcurrent protection/ungrounded conductors that is free to use for line to neutral loads.

May not actually be quite that simple but is the direction you go with that.

I ran a 600 amp feeder to a HVAC equipment room at a school building. All the HVAC equiment was three phase no neutrals. We did have some 120 volt lights and a general use 120 volt receptacle to supply in there as well - even with several empty spaces in the panel and consideration of possible future 120 volt loads -I figured with the 400+ amps of three phase load already being supplied there still would be no need for a feeder neutral larger then the minimum size EGC needed - there just wasn't that kind of capacity left on the feeder to add such loads.
Click to expand...

I'm with ya now.

JAP>
 
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