# Aluminum 2-2-4 vs 2-2-2 and 4/0-4/0-2/0 vs 4/0/40/40



## Doc13067 (Dec 2, 2021)

I’ve been an electrician for a long time now but I’m embarrassed to say this is something I’ve struggled with and whenever I ask someone I never get a satisfactory answer. When I do a 100 amp service with SEU cable it’s 2-2-4 Al. When I do a 200 amp service is 4/0-4/0-2/0 Al. When I buy individual wires to run through conduit I’m told all 3 service wires must be the same size and the neutral cannot be 2 sizes lower (like it is in the SE cables). Can anyone put this to bed for me? For resi services can a 100A neutral be #4 and a 200A neutral be 2/0? They come on spools that way with the neutral wire being smaller and I know the obvious that the two ungrounded conductors are bringing back most of the load and the grounded conductor is just whatever is left over that wasn’t canceled out by the 2 hots so I just want to find out once and for all so I can know For sure I’m buying the right stuff. I’d hate to find out that all this time I should not have been getting the cables with the smaller neutrals. Thanks so much!


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## David Detmer (10 mo ago)

Who told you that you can’t undersize a neutral when using separate conductors? I have to assume this person was just gossiping, because he surely didn’t give you a code reference.

I’ve been using 2/0 XHHW for the neutral for 200 amp service changes for 20 years. I don’t do it for the cost savings as much as for the ease and convenience of not having to ring out the conductors afterwards when I inevitably forget to tape up the neutral before I push it in the pipe. It’s nice knowing with 100% certainty which conductor is the neutral.

Depending how you calculate the load, you could use an even smaller neutral in many cases.


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## Almost Retired (Sep 14, 2021)

first of all as you noted, a reputable mfg or sh will not sell something illegal
secondly as you noted, it is nearly impossible to load up the neu, particularly in a service or sub panel feeder

my area is still on 2014 NEC

table 250.102(c)(1)
this shows the largest un-grounded conductor which requires a min. grounded conductor size of ......
for instance #2cu needs #8cu

there is another table further on for min. EGC and a note that the neu should be larger than it

be aware that many ppl will argue to the death no matter what proof or logic you show them

there is one instance where you may want to increase your neu size
this is harmonics, you cant read them with your normal meter
but they add current to the neu side of any power supply
led lites for example, UPS, big office printers
but since you cant read them, you will need a construction type elect engineer to specify whether you need to up size the neu
Southwire mfg is already making 12-2G with a 10AWG neu

i look for that to be the norm in years to come


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## Doc13067 (Dec 2, 2021)

Ok thank you Guys. So the neutrals that come in SE cables and on a spool of triplex are actually larger than they need to be. For example aluminum 4/0 only calls for #2 but we get 2/0 in SE cable or pre made spools of 4/0-4/0-2/0 triplex and aluminum #2 only calls for #6 but we get #4 in SE cable or pre made spools of 2-2-4 triplex. the word triplex in my sentences is not meant to mean poco ASR triplex, just that 3 wires are twisted together pre spooled and ready for pulling.


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## Doc13067 (Dec 2, 2021)

David Detmer said:


> Who told you that you can’t undersize a neutral when using separate conductors? I have to assume this person was just gossiping, because he surely didn’t give you a code reference.
> 
> I’ve been using 2/0 XHHW for the neutral for 200 amp service changes for 20 years. I don’t do it for the cost savings as much as for the ease and convenience of not having to ring out the conductors afterwards when I inevitably forget to tape up the neutral before I push it in the pipe. It’s nice knowing with 100% certainty which conductor is the neutral.
> 
> Depending how you calculate the load, you could use an even smaller neutral in many cases.


not to mention the ease of pulling it through 2 inch pipe.


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