From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Dirty Shore Power
Message-ID: <u0707vocvc4fjfj8ta7f0of0ku364i03m4@4ax.com>
Date: Thu, 13 Mar 2003 01:01:57 -0500

On Sat, 8 Mar 2003 04:42:09 -0600, "pewsplus" <pewsplus@bellsouth.net> wrote:

>Recently had a bad experience while connecting to shore power in Ga.
>campground.
>
>Shortly after connecting to the 50 amp shore power plug at Jones RV in
>Norcross, GA, wife came out to report smelling smoke in the galley of our
>MH.
>
>On investigation, we discovered that the micro/convection oven, main TV and
>VCR were fried. Had electrical system checked the next day by a dealer. The
>technician confirmed, to our relief, that the MH electrical system was not
>damaged but that we had lost the micro, TV and VCR. He states probable cause
>as either a power surge or a mis-wired 50 amp plug which was actually
>putting 220 volts into the coach.

Remote possibility that the neutral and one hot leg is reversed in the CG
plug.  More likely a faulty neutral leg somewhere in the power distribution
which can cause high voltage to appear on one leg or the other under certain
conditions.

>
>Anybody have any similar experience?

No. I always check the pedestal voltage with my little homemade dual voltmeter
before I plug in.  Can't recall ever finding a problem but I check
nonetheless.

>
>Any recommendations on preventing a repeat?

Sure.  a) Get and learn how to use a digital voltmeter and then check each
pedestal for proper voltage before you plug in. (In the alternative, have
voltmeters installed in the rig and always leave the main breaker off until
you verify the proper voltage)  b) Install (or have installed) suitably rated
120 volt MOVs between the hot legs and the neutral to clamp the voltage to
just above 120 volts until the pedestal breaker trips.  c) Install (or have
installed) a high speed overvoltage trip relay to isolate the RV in the event
of overvolage.  Must be high speed to avoid smoking the electronics stuff
before it operates.

If you do a) reliably, b) and c) are not necessary.  If you do b) then I
recommend also doing c).

>Any recourse?

Recourse?  As in trying to find someone else to blame for your carelessness in
not checking the voltage first?  Oh I'm sure you can confront the CG operator
and he'll pay for your carelessness for fear of being sued.  Of course too,
maybe that will be the straw that breaks the camel's back and makes him close
the CG and retire to Florida.  Or raise the rates for your next visit.

Why not just write it off as a "lessons learned" and go on?

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Dirty Shore Power
Message-ID: <v6k17vsjt8hftnvp73g8tgend5vf8rhe2c@4ax.com>
Date: Thu, 13 Mar 2003 13:49:22 -0500

On Thu, 13 Mar 2003 11:19:09 -0700, Alan Balmer <albalmer@att.net> wrote:

>On Thu, 13 Mar 2003 01:01:57 -0500, Neon John
><johngdDONTYOUDARE@bellsouth.net> wrote:
>
>>Recourse?  As in trying to find someone else to blame for your carelessness in
>>not checking the voltage first?  Oh I'm sure you can confront the CG operator
>>and he'll pay for your carelessness for fear of being sued.  Of course too,
>>maybe that will be the straw that breaks the camel's back and makes him close
>>the CG and retire to Florida.  Or raise the rates for your next visit.
>
>Or, if there actually *is* a problem with the wiring, maybe he could
>just fix it?

I'm sure the CG owner will fix the problem if there is one.  Particularly this
CG, as it is a pretty nice one.  This guy was asking about what recourse he
has.  Quite different issue.

>
>I agree that it is wise to check the CG wiring before hooking up, and
>I always do. However, I don't think it's unreasonable for a naive user
>to expect that the wiring is correct, or "carelessness" if they don't
>check.

Only unreasonable if you don't mind replacing your appliances every so often.
Yes, the power should always be right.  Just like there should be no disease
or war or ....

>
>When you buy gas, do you verify its octane rating with your handy
>portable octane tester? Or do you just stick the nozzle in and start
>the pump?

Why yes, yes I do.  When it matters.  Such as racing in a class that requires
pump gas.  The gadget is called a gas chromatograph.  I built my first one for
gas analysis in 1972.  Now I just use a Hewlett-Packard.

This is a great analogy but not in the way you wanted.  When the downside of
NOT checking involves damaged hardware (burned out microwave, blown engine)
then checking first is mandatory.  When the consequences are minor (knock or
lower performance) why bother?  Putting gas in my street car is the latter.
Plugging your rig into an unknown power outlet is definitely the former.

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Dirty Shore Power
Message-ID: <5iv17v4bt05q6086762jdijopk7njegirm@4ax.com>
Date: Thu, 13 Mar 2003 17:23:08 -0500

On Thu, 13 Mar 2003 12:54:50 -0600, "pewsplus" <pewsplus@bellsouth.net> wrote:

>John said:
>> >Any recommendations on preventing a repeat?
>>
>> Sure.  a) Get and learn how to use a digital voltmeter and then check each
>> pedestal for proper voltage before you plug in.
>
>Thanks John ... I have a digital volt meter but need some instruction on
>which connector(s) on the 50 amp plug to test and what they should read.

Easy enough.  Place the meter on ACV and the nearest range above 240 volts.
Usually 250 or 500 volts.  Put the black wire on an earth ground other than
the pedestal.  The water hydrant will work fine - even in plastic pipe the
water is conductive enough for a high impedance meter.  Probe each hole in the
socket in turn with the red lead.  In a 50 amp socket, the round pin and the
blade opposite it should read near zero volts.  The round pin (ground) should
be very near zero while the blade opposite (neutral) may rise a little
depending on the CG load distribution.  The two side blades should each read
120 volts, plus or minus, to ground.  Then probe the side blades, the black
lead in one and the red in the other.  it should read 240 volts plus or minus.

If the neutral is open between the CG wiring and the pole (or pad) pig, the
most common problem, one side blade will read much more than 120 and the other
will read much less.  The leg with the most load on it will read the lowest.
This is to be avoided!  If the load is high enough on one leg or one leg
shorts, the other leg will have the full 240 volts on it.

Very rare is the neutral and one hot leg getting reversed.  If that happens,
one side blade will read near zero and the neutral (opposite the pin) will
read 120 volts.  Any load in your RV connected between the OTHER leg and
ground will experience 240 volts hot to neutral.

These checks can be made literally in less time than it took to read this.

If you travel a lot I recommend making up a test box for the purpose.  Back
when I was doing a lot of concessions out of my restaurant I made up a box
using analog edge-reading voltmeters.  Four of these fit in a standard
handibox with a cord coming out, ending in the plug.  A single wire with an
alligator clip also exits the box and supplies ground reference for all 4
meters.  Simply plug it in, connect the alligator clip to ground and read all
4 legs at once.

As my eyesight declined I made up a new one using miniature digital panel
meters.  Dated and others make such meters that are inexpensive (about $40 ea)
and about the size of a small match box.  They read directly in AC volts.
Again, four of those will fit in a standard electrical wiring handibox
(surface mount switch or outlet box.)  For everywhere I have traveled in the
East, a steel bridge spike (tent spike) pushed into the ground has provided
ample ground reference if a faucet wasn't handy.  May or may not work in the
dry (mid) west.  Many times if it's humid I can merely hold the ground lead
and provide sufficient ground path back to earth.

I keep the box in the compartment where the cord is stowed.  Simple matter to
get it out, plug in the pedestal and stick it back in.  Adds oh, 15 seconds to
my hookup routine.

>
>No, I didn't check the pedestal voltage, didn't know I should. I didn't
>check the sewer pipe for leaks either nor do I know that it is
>environmentally correct.
>
>Some thing you just assume to be correct.

And most of the time you get away with it.  Occasionally you don't.  At that
point you either alter your routine to help prevent a repeat or you accept the
risk and the loss and go on.  As a retired nuke and coming from the culture
where no identifiable failure mode is tolerable and having seen the electrical
crap that I have, I choose to move my protective radius out just a little
farther than most.

BTW, I don't check the sewers either but then again, a bad sewer won't burn
out all my appliances, set my rig on fire and potentially kill me.  I DO check
the water in places where the circumstances leads me to suspect its quality -
such as way out in the boonies where there is obviously no city water.  The
risk of city water being bad is sufficiently low as to be acceptable to me.

John