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+--- Thread: Hot skin-potential shock (/showthread.php?tid=751)
Hot skin-potential shock - Ralph L. Fullenwider - 06-01-2005 03:24
Hello everyone:
Earlier a thread on hot skin surfaced, and this is something that will not
only be a shocking experience but can actually kill you or a family member,
as has been reported in several RV articles in the past.
The hot skin, in the Coach, stems from the neutral and ground bonding
somewhere in the AC electrical system.
How does one go about finding this problem? Lets explore it a little deeper
and test for it.
1. With the Coach on shore power and on a known good grounded 110 VAC
circuit, place a ground rod at least 18 inches deep into the dirt near the
entry door. Then with a multimeter, attach the black lead tot he ground
rod, set the meter to VAC and touching the red lead tot he entry door frame
in several places, the meter should read 0 VAC, anything other than a 0 VAC
reading tells you there is a hot skin in the Coach.
Ok let's find this potential hazard:
1. With all shore power removed and gen set not running and the transfer
switch in the off position we can safely start checking for the neutral to
ground bonding in the Coach.
2. Remove the cover from the electrical circuit breaker box in the Coach.
Set your multi-meter to the ohms scale and place the black lead on the bare
copper grounding strip and place the red lead on the white (neutral)
bonding strip and the meter should read open or INF or Meg ohms. If you
have a 0 that means you have continuity between the two and we go to the
next step.
3. Leaving the black lead in place on the bare copper bonding strip. Start
at the bottom or top of the white (neutral) bonding strip, loosen the white
wire and separate it from the bonding strip and check the ohms between that
white wire and ground and then again check the neutral bonding strip once
again. If the reading on the meter is INF or Meg ohhm on the single wire
then that circuit is not the source of the problem. Re attach that white
wire and go to the next one, removing it and doing the ohms check. And so
forth until you find the source of the ground to neutral bonding. You will
know you have found it ( and there may be more than one) when your meter
reads 0 ohms or continuity. This separates all the different circuits in
the breaker box and allows you to isolate the problem circuit.
4. Once found, then you need to trace that circuit out to find where the
white wire is touching the grounded box or appliance. Fix it and then go
back to the breaker box and check from ground to neutral bonding strips to
be sure there are no other circuits causing a problem. Coach electrical
heaters are a good source for the neutral to ground bonding. A wire nut may
have burned through allowing the white wire to touch the grounded metal box
or a connection in a duplex box has loosened up to allow the white to touch
the grounded box.
5. Once the problem has been found, then hook shore power back up and set
your meter to VAC and going back to the entry door, re attach the black
lead to your ground rod and using the red lead on the door frame, check in
several places once again and now your meter should read 0 VAC, meaning
that you have repaired the "hot skin," and you and your family members are
safe.
This is a very time consuming ordeal, to be sure, but one well worth taking
the time to find and repair. Hope this helps.
Safe travels,
Ralph and Charolette Fullenwider
Dream_35_Team
'85FC35 in Oklahoma
Ralph's RV Solutions
http://home.swbell.net/rlf47/index.htm