[aprssig] Generators, grounding, recessed male twistlock,etc.

Jim Lux jimlux at earthlink.net
Mon Feb 6 13:42:49 EST 2006

Message: 4
Date: Sun, 05 Feb 2006 14:41:48 -0500
From: Joe Della Barba <joe at dellabarba.com>
Subject: Re: [aprssig] Generators, grounding, recessed male twistlock,
To: TAPR APRS Mailing List <aprssig at lists.tapr.org>
Message-ID: <43E654FC.5040205 at dellabarba.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I used to be in the marine electrical/electronic business. Generators on
boats always had the neutral connected to the chassis of the genset as
well as the ships ground. Another requirement was that there would be NO
breakers or switches in the ground lead.


Precisely, and the same would typically be true of "temporary power" 
(construction site).. but in a standby/backup power situation (as in 
powering your house or business or remote transmitter site) with a transfer 
switch, you DON'T want the bonding between neutral and ground at the 
generator.  The *one* bond between "grounding conductor" (green wire) and 
"grounded conductor" (neutral, white wire) would normally be at the 
transfer switch, or at the service entrance. [Or, you use a 3 pole transfer 
switch which transfers neutral too.].

The problem comes in with generators designed and sold for "temporary 
power" use (typically with a receptacle on them to get the power out) which 
often have the chassis (ground) and neutral bonded internally.  Generators 
designed for "backup power" usually have a terminal strip or separate 
wires, and it's up to the installer to bond or not bond as appropriate.

The underlying problem is that if you have two places where ground and 
neutral are connected, then current can flow through the safety grounding 
circuit, which is muy bad.

We won't even get into the arcana of proper application of ground fault 
interrupters in temporary/backup power systems.

Moral of the story: Ask someone who knows, and who can look at YOUR 
specific application. RVs, boats, construction sites, and houses are all 


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