DC-GFP/2 protection [RE-wrenches]

[Bill Brooks]

Matt,

Remember that the AC neutral is almost always grounded at the service
entrance so the whole system is still referenced to ground. When we unground
the DC negative of an SW, there still may be conductive paths within the
inverter that connect the system to the AC neutral which is always grounded
in the US. SOVs and other surge protection is what really saves electronics,
not grounding or ungrounding. The issue is voltage differential across
semiconductors and other sensitive electronic components, if you keep the
difference down, things survive. If you allow a large differential, things
blow up. Grounding can contribute to the voltage differential or reduce the
differential--it's all in the design.

Bill.


-----Original Message-----
From: matthew tritt [mailto:solarone at charter.net]
Sent: Thursday, August 22, 2002 9:58 PM
To: RE-wrenches at topica.com
Subject: SPAM: Re: DC-GFP/2 protection [RE-wrenches]


Ray et all,
I just have to chip in a few cents worth on this one too!

Coming from the "old school" of solar guys and also coming from the
wonderful world of boat and yacht DC, I was taught that you never-ever
connect the AC (shore power) and DC neutrals together. Period.
The reasons for this are a little different than (maybe) what we're talking
about with land-based systems, and have to do more with potential for
electrolysis than lightning. Neither AC nor DC is "grounded" to water to
prevent unwanted current flow and the resulting damage it can cause. But,
the rigging (see solar array and turbine tower) is always grounded to water
to shunt lightning strikes away from the electrics (and people).

I would call this a genuine floating neutral. (Yee-haw)

But seriously folks, why don't we do what the rest of the world does in
regards to the bonding issue?

Matt

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