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

[Drake]

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:j...@renewableassociates.com>j...@renewableassociates.com
www.renewableassociates.com
REAL_logo_black2




From: re-wrenches-boun...@lists.re-wrenches.org 
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Drake
Sent: Wednesday, June 19, 2013 6:42
To: re-wrenches@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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