[RE-wrenches] Neutral sizing

[Garrison]

Hi Jay,

Is this for an inverted output circuit? If so then I think the NEC reference you’re looking for is 705.95(B).  That says you can size the neutral to the same size as the EGC if the neutral is used only for instrumentation, voltage detection or phase detection. 

A number of single phase inverters these days do not require a neutral at all, so if the AHJ will not accept downsizing it may be worth changing inverters.

Garrison 

> On Sep 22, 2018, at 6:07 PM, Glenn Burt <glenn.burt at glbcc.com> wrote:
> 
> Here is the code reference explaining this conductor size disparity from 2017 NEC:
> 
> "According to Table 310.15(B)(16), a 3/0 AWG, Type THW copper conductor
> has an ampacity of 200 amperes. However, for a 3-wire, single-phase
> dwelling unit service, as shown in Exhibit 215.2, 310.15(B)(7) permits a
> service conductor (or a main power feeder conductor) with an ampacity
> of 83 percent of the service rating. This permits a minimum of 2/0 AWG,
> Type THW copper conductors or 4/0 AWG, Type THW aluminum conductors
> for services or a main power feeder rated at 200 amperes"
> 
> -Glenn
> 
> -----Original Message-----
> From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> On Behalf Of Dana
> Sent: Saturday, September 22, 2018 10:32 AM
> To: 'RE-wrenches' <re-wrenches at lists.re-wrenches.org>
> Subject: Re: [RE-wrenches] Neutral sizing
> 
> What about 4/04/02/0 aluminum, service feed? Or is that utility excepted?
> 
> ----------------------------------------------------------------------------
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> 
> -----Original Message-----
> From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> On Behalf Of Marco Mangelsdorf
> Sent: Friday, September 21, 2018 10:39 PM
> To: 'RE-wrenches' <re-wrenches at lists.re-wrenches.org>
> Subject: Re: [RE-wrenches] Neutral sizing
> 
> At the risk of sounding like a grandpa Wrench...I've never had or seen a neutral conductor be smaller than current carrying.
> 
> marco
> 
> -----Original Message-----
> From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jay
> Sent: Friday, September 21, 2018 3:47 PM
> To: re-wrenches at lists.re-wrenches.org
> Subject: [RE-wrenches] Neutral sizing
> 
> Hi all,
> 
> I’m wondering if there is code reference to size of neutral vs power conductors. 
> 
> County is requiring neutral same size as mains 240vac. 
> As it’s 500 mcm due to VD (200 amp service) it’s a non trivial expense. 
> 
> I know that where I live, the utility brings in a smaller neutral than L1/L2
> 
> Thanks in advance
> 
> Jay
> 
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