[RE-wrenches] Full sized neutral - 240 V inverter

Drake drake.chamberlin at redwoodalliance.org
Wed Jun 19 12:55:45 PDT 2013


A very common cable for 100 A service conductors has 2 - #2 AL wires 
and 1 - #4 AL for the neutral;  200 A will have 2 - 4/0 AL wires and 
1 - 2/0 for the neutral.   If I run # 2 to limit the VD on the run to 
the panel and reduce the neutral to #4, #12 copper phase and neutral 
will still connect to the inverters.  This would be code for a feeder 
to a separate structure.

Does the Power One inverter actually have a major imbalance resulting 
in substantial neutral currents? If so, it is really a 120 V inverter 
for VD calculations.


  03:37 PM 6/19/2013, you wrote:
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>
>Doug,
>705.95(B) allows you down size your neutral if it is used solely for 
>instrumentation and it must be sized equal to or larger than the EGC 
>but this is not the case. If Power One says a full size neutral is 
>needed than that means that it is not just a voltage sensing 
>conductor used for instrumentation and that it does carry current.
>
>I don't believe there are any exceptions in code for downsizing your 
>neutral in regards to upsizing the conductors to account for voltage 
>drop but I could be wrong.
>
>--
>John Stimac | Corvallis, OR
>Renewable Energy Associates LLC
>541-754-2001 Office/Fax
><mailto:john at renewableassociates.com>john at renewableassociates.com
>www.renewableassociates.com
>REAL_logo_black2
>
>
>
>
>From: re-wrenches-bounces at lists.re-wrenches.org 
>[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
>Sent: Wednesday, June 19, 2013 6:42
>To: re-wrenches at lists.re-wrenches.org
>Subject: [RE-wrenches] Full sized neutral - 240 V inverter
>
>Hello Wrenches,
>
>Power One tech support said that full sized neutrals had to be run 
>to a pair of 240 V, PVI 3.6 inverters.  We have a 180 foot 
>underground run to the service panel.
>
>Why do we need to run a full sized neutral all the way back to the 
>panel?  The wiring to the panel is oversized for voltage drop.  The 
>code allows for reduction of neutral size where neutral imbalance is 
>less than the current of a phase, which is usually the case.
>
>Why does a neutral need to be installed that is the size of the 
>phase wiring where the imbalance should be negligible? Or is there a 
>lot of neutral current for some reason?  Am I missing something?
>
>Thanks
>
>Drake
>
>
>Drake Chamberlin
>Athens Electric LLC
>OH License 44810
>CO License 3773
>NABCEP Certified Solar PV Installer
>740-448-7328
><http://athens-electric.com/>http://athens-electric.com/
>
>
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