PV Negative color [RE-wrenches]

[Ray Walters]

<x-flowed>


Lets follow code to the letter while wiring a positive grounded  
system. First positive is white, not striped but it could be just  
white. Then code allows the ungrounded conductor ( the negative) to  
be red, black, blue, etc.. So we could have a code compliant system  
with negative marked red, and positive marked white.
Doesn't it seem like its time to fix the code again?
I agree with John, that we can't have homeowners thinking high  
voltage DC is something they can be playing with, and code has more  
restrictions for DC voltages over 50 vdc. Warnings of High voltage  
work AC or DC.
What code doesn't have and needs desperately is to identify the  
positive and negative conductor in a DC system. Code only addresses  
identifying the grounded conductor. Code is treating DC systems like  
AC, and we in the PV business know what a mistake that can be. The  
polarity issues just are NOT the same for AC.

I wish someone from Outback, Xantrex, or Magnum would weigh in on  
this and explain why they also color code DC the same as automotive.
A point I don't agree with John is that red and black are a  
violation. First think of all the UL listed equipment from the afore  
mentioned manufacturers.
Second,  code allows systems (with many restrictions) to not ground  
one of the conductors. THus red and black are appropriate code  
compliant colors in those systems.
RVs for instance can't truely ground the system, as the system is  
suspended from the ground by rubber tires.

Red for positive, black for negative, white stripping (but not solid)  
for which ever is grounded, should work for everyone.

Ray


On Dec 7, 2007, at 11:35 AM, John Berdner wrote:

>
> Wrenches:
>
> Over the years I have spent many hours discussing this issue with John
> Wiles.
> The Code requires grounded neutral conductors to be white.
> The Code makes no distinction between AC or DC on this issue.
> The Code also does not differentiate the white color requirement for
> solidly grounded neutrals or ones with GFDI devices installed.
>
> The red and black automotive "standard" is not applicable or
> appropriate for home sized.
> The last thing I would want is someone to think that a 480 Vdc PV
> system was 12 Vdc was 12 Vdc because of the wrong color wires.
> I also think choice of red and black would be a very difficult  
> decision
> to defend in court since it is a clear violation of the NEC.
>
> Yes, during a ground fault the neutral can become hot at anything  
> up to
> Voc relative to ground.
> This is the exact reason for UL labeling requirement on inverters and
> for my repeated cautions about troubleshooting a system with a ground
> fault.
> Even if both PV positive and PV negative are disconnected, everything
> on the array side of the GFDI device can still be at this potential.
> No matter how close you move the GFDI there will still be some wires
> that could be energized during a ground fault.
> Moving the GFDI closer to the array adds costs in both hardware and
> installation time.
>
> Best Regards,
>
> John Berdner
>
>>>> Drake.Chamberlin at redwoodalliance.org 12/7/2007 09:24:56 AM >>>
>
> At 08:22 PM 12/6/2007, you wrote:
>
>> I think that a solidly grounded conductor should be
>> white, or not, BUT when working with systems using a
>> ground fault breaker or fuse and is therefor a fused
>> grounded conductor, it should not be white. If a
>> ground current makes the wire hot, don't call it
>> grounded. If the only way it can become hot is when
>> it is broken then it can be called grounded.
>
> This sounds right. The negative wire can exist in junction
> boxes, and if it is white and operating at high voltage DC due to
> the normal operation of the ground fault device, it could pose a
> serious hazard to electricians troubleshooting other systems.
>
> The automotive and marine designations of black and red are
> problematic, due to the fact that black is often positive in NEC
> compliant wiring. Maybe yellow would be a good recommendation for
> negative. The not-always-grounded negative wire on a PV ground fault
> system is a unique, as far as I know.
>
> A far better ground fault system would be one that opened the
> conductors at the array, instead of at the end of the run, where a
> ground fault could continue indefinitely. Control wires could be run
> through the mandated metal conduit to the control center. A hot
> neutral would not be a likelihood.
>
> The 2008 code has new rule to limit the existence of hot, white wires
> by requiring all multi wire branch circuits to open all conductors
> simultaneously. That means that if you are working on a split 240
> volt circuit or a 120/208 Volt 3 phase, all circuit conductors will
> open with a 2 or 3 pole breaker, and it will be safe to disconnect
> the neutral anywhere in the system. As this method becomes mandated,
> the electricians are liable to feel too safe with white wires.
>
> Drake
>
>
>
>
>
>
>
>
>
> --
> [Non-text portions of this message have been removed]
>
>
> - - - -
> Hosted by Home Power magazine
>
> To send a message: RE-wrenches at topica.com
>
> Archive of previous messages: http://lists.topica.com/lists/RE- 
> wrenches/read
>
> List rules & how to change your email address: www.mrsharkey.com/ 
> wrenches/etiquette.php
>
> Check out participant bios: www.mrsharkey.com/wrenches/
>
> Moderator: michael.welch at homepower.com
>
>

R. Walters
Solarray.com
NABCEP # 04170442	




--
[Non-text portions of this message have been removed]


- - - -
Hosted by Home Power magazine

To send a message: RE-wrenches at topica.com

Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read

List rules & how to change your email address: www.mrsharkey.com/wrenches/etiquette.php

Check out participant bios: www.mrsharkey.com/wrenches/

Moderator: michael.welch at homepower.com
--^----------------------------------------------------------------
This email was sent to: michael.welch at re-wrenches.org

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

For Topica's complete suite of email marketing solutions visit:
http://www.topica.com/?p=TEXFOOTER
--^----------------------------------------------------------------


</x-flowed>