Reduced neutral popularity - residential

[mark32]

Just wondering how many reduce the neutral when, for example, feeding a sub panel in a residential setting? I don't ever recall anyone on a resi job contemplating this but just recently I overheard a couple of so-called electricians talking about going down a size on the neutral for this very situation. (I only say so-called electrician because of the rest of the conversation I heard these guys discussing)

 

[ActionDave]

Most every time for me the neutral is reduced. If it is a full size it because of job specs.

 

[kwired]

Lets use a 100 amp feeder as an example.

How often do you see a 100 amp feeder in any type of application, residential, commercial, industry..., where you have 100 amps flowing on one ungrounded conductor only. Chances are there is current on the other ungrounded conductor(s) also that is going to end up reducing what the grounded conductor sees. (exception being two phases and neutral of a wye system)

Now throw in a few 2 or 3 pole circuits that don't use a neutral conductor and you have current on ungrounded conductors that is not seen by the neutral.

Not really that often is the neutral ever going to carry same maximum level of current as the ungrounded conductors.

 

[Rewire]

alot would depend on the loading of the subpanel if the primary function of the sub was to feed 240V loads then I would probably downsize

 

[Dennis Alwon]

I almost always downsize unless I just happen to have enough of the larger cable and none of the smaller. For 200 amps I usually use 1/0 copper and 2/0 for ungrounded conductors. Now that copper is so high I have gone to using 4/0 and 2/0 alum.

I have not done a 100 amp service on a house in 30 years and I think then it was 125 amps.

I never had the desire to try and go with #4 copper on a 200 amp service although it would probably be more than enough in most cases.

 

[John120/240]

Reduced neutral in residental applications ? For residental isn't the majiority of wiring done in

Romex or cable types of wire ? So isn't the neutral size already determined by the cable that

feeds the sub panel ?

 

[mark32]

Thanks for the replies, I see it's more popular than I thought.

Reduced neutral in residental applications ? For residental isn't the majiority of wiring done in

Romex or cable types of wire ? So isn't the neutral size already determined by the cable that

feeds the sub panel ?

I didn't make it clear but I meant if you were to run your conductors through a raceway.

 

[Ponchik]

99% of the time the neutral on my service upgrades is unless it is prohibited by the AHJ. Usually 200A panel gets (2) 2/0 and (1) #1.
Also the AHJ that allow it do require a service load calculation.

 

[LEO2854]

Thanks for the replies, I see it's more popular than I thought.




I didn't make it clear but I meant if you were to run your conductors through a raceway.

Well I have never done that or even given it any thought but after reading Dennis's post I will consider it.

 

[ActionDave]

Thanks for the replies, I see it's more popular than I thought....

More popular for good reason. Look at Kwired's post again if you, or anyone else, has any remaining doubt.

 

[iwire]

Reduced neutral in residental applications ? For residental isn't the majiority of wiring done in

Romex or cable types of wire ? So isn't the neutral size already determined by the cable that

feeds the sub panel ?

The SE / SER cable sold in my area has a reduced neutral.

 

[Ponchik]

The SE / SER cable sold in my area has a reduced neutral.

Do manufacturer make different cable for different regions of the country? I have never noticed if local SER has reduced neutral.

 

[Dennis Alwon]

Do manufacturer make different cable for different regions of the country? I have never noticed if local SER has reduced neutral.

You can get ser with a reduced neutral from Southwire however I have not seen it and it is not available in all sizes. SEU of course can have a reduced egc but not usually the neutral

Here is a southwire spec

 

[kwired]

I don't know if it is fact or not but have been using a general rule pretty much ever since I got into the trade. That rule has always been the neutral can be two sizes smaller than ungrounded conductors where it is carrying imbalanced current without having to show calculations of the load on the neutral. I generally do follow this practice and never been asked to prove neutral current. This typically is only for feeders and services, a MWBC is easily going to have same current on neutral as on either ungrounded at some time.

 

[texie]

I don't know if it is fact or not but have been using a general rule pretty much ever since I got into the trade. That rule has always been the neutral can be two sizes smaller than ungrounded conductors where it is carrying imbalanced current without having to show calculations of the load on the neutral. I generally do follow this practice and never been asked to prove neutral current. This typically is only for feeders and services, a MWBC is easily going to have same current on neutral as on either ungrounded at some time.

I think some of us older guys do this and in general I do the same. I could be wrong, but I think this was in the code at one time. Now I'm curious-can anybody confirm this?

 

[Rewire]

I think some of us older guys do this and in general I do the same. I could be wrong, but I think this was in the code at one time. Now I'm curious-can anybody confirm this?

I dont remember it but I have only been in the trade a few years