grounding array/sunny boy [RE-wrenches]

[Rob Wills]

Windy - as one of the NEC writers.. There has been a provision for
ungrounded arrays going back to the first Article 690 in 1982.  It was
originally written as an exception to 690-41.  We incorporated the exception
into the body text in the 2002 code, and tried to smooth the language to
make it clearer that this is allowed.

It's now up to UL to work out what "equivalent system protection" is - and
that will soon be resolved.  You will likely see non-isolated inverters
coming to market in the USA this year.

We believe that non-isolated inverters are inherently safer than
hard-grounded, or current-detect grounded systems.  Grid power feeding back
to the array has enough energy to open fuses quickly. Ground fault detect
schemes are easier to implement, and arrays can be safer to work on when the
inverter is disconnected.

This is a big philosophical change for our industry, but an important one.

When anyone questions me as to this path, I say "what would a variable speed
motor drive manufacturer say if the NEC told them to hard ground the motor
windings?"...

Regards

Rob Wills

-----Original Message-----
From: Windy Dankoff, Dankoff Solar [mailto:windy at dankoffsolar.com]
Sent: Monday, January 14, 2002 2:08 PM
To: RE-wrenches at topica.com
Subject: RE: grounding array/sunny boy [RE-wrenches]


>My opinion is to float the array. ...   ....   ...
>There are many more benefits, but this would turn into long
>dissertation.
>
>Regards.
>____________________________________________
>Kent Sheldon
>Manager, Industrial Power Systems
>SMA America


Thanks, Kent!

Any other agreement out there?

Is anybody urging NEC writers to change the rule?

Windy

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