Date: Wed, 11 Jul 2012 13:49:39 -0400
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: re-doing unsafe 120 volt wiring, add GFCI?
In-Reply-To: <CAH32RNZ_kGEjuBkAHMzs19+zLDCbMBTmCTik-KY4K6b_X3OckQ@mail.g
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At 12:33 PM 7/11/2012, Loren Busch wrote:
>While on this subject let me add an additional safety suggestion. Get a
>line tester and/or a 120v plug in meter. Both are avialable from places
>like Camping World. And use them to test the shore power you are plugging
By line tester I imagine you mean the three-prong plug containing
three neon lights, which will tell you whether hot and neutral are
reversed, and neutral or ground open.
It's an useful tool, and I heartily endorse carrying and using
one. However it's got an important limitation for testing power
connections, which is that it places only a tiny load on the circuit,
so it won't give you any warning of a poor connection.
A solenoid meter (electricians call them "Wiggys" for historical
reasons) like this one
http://www.grainger.com/Grainger/wwg/search.shtml?searchQuery=wiggy&op=search&Ntt=wiggy&N=0&GlobalSearch=true&sst=subset
will put a bit more load on because it indicates voltage by actually
pulling a solenoid core down against a spring, like a lightweight
spring scale. It's more nuisance to use and costs more, and you have
to understand or write down a table like the one printed on the
little plug-in guy, but does give some indication whether the ground
or neutral connections can actually carry some current -- if it shows
a different reading hot-neutral vs hot-gnd, for example, you know
there's a problem in the one with the lower reading.
If you look at a standard three-prong socket, think of it as a little
man's face, with the U-ground opening his mouth and the two slits his
eyes. His left eye (on your right as you look) will be shorter, and
that's HOT. His right eye is NEUTRAL and his mouth is PROTECTIVE GROUND.
A correctly wired socket will show H-N 120 V; H-G 120 V; N-G 0 V.
Hot-neutral reverse (the common problem) will show H-N 120 V; H-G 0
V; N-G 120 V. I would not recommend to connect to this, as devices
like table lamps which are wired to keep the hot terminal protected
will now have it exposed, or more exposed.
Open ground will show H-N 120 V; H-G 0 V; N-G 0 V. I would strongly
recommend not to connect to this, as any faults or leakages in
devices including van wiring will cause the van chassis to become hot
with respect to earth.
Open neutral will show H-N 0 V; H-G 120-240 V; N-G 0 V. In a house
or campground wired US-fashion this is a dangerous situation which
can start fires in small. DO NOT CONNECT to this. I'll explain why
separately.
Ground-neutral reverse will meter as normal. This is not a good
situation but unless I'm forgetting something I don't see how you can
tell from the socket.
There's another instrument that saves electricians' and telephone
linemen's lives - a non-contact voltage detector like this:
http://www.grainger.com/Grainger/FLUKE-Voltage-Detector-2KU25?cm_sp=IO-_-IDP-_-BTM_BTB05209020&cm_vc=IDPBBZ2
Hold it next to something that's got 50 VAC or more sitting on it and
it will complain.
Versions of both of these will be available at your local
electricians supply house and probably at H-D/Lowes etc as
well. Both good investments for dealing with AC supply circuits.
And to the original question, I think a GFCI is a good idea.
Does the Westy really have a 6-ga bonding wire? I'm surprised they'd
use one so large (but I know zip about Codes...).
Yours,
David