PV Negative color [RE-wrenches]

[Drake Chamberlin]

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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


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