| Author |
Message |
bobm
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 28, 2005 - 9:59 pm: | |
I had my unit plugged in with an adapter to fit my shore power cord to a house 110 outlet.
House outlet had no ground so I used another two prong adapter. With my bare knees on the ground I felt a significant shock when checking tire pressure. Shoes provided enough insulation that i did not get a shock. Do I have a wiring problem or is it just the lack of a good ground? |
TWODOGS (Twodogs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 28, 2005 - 10:06 pm: | |
yes |
John Jewett (Jayjay)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 28, 2005 - 10:11 pm: | |
Lack of an equipment ground IS a wiring problem. It sounds like you may also need to balance you electrical load, since the shock you received was probably the Potential Difference between the two phases. Get some one that at a minimum, knows which end of a wiggy is hot, or preferably has a good digital volt meter, and get it done properly. We want to see you back here on the 'Board, and not get a "For Sale" notice from your widow.
...JJ |
Jerry Liebler (Jerry_liebler)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 28, 2005 - 10:16 pm: | |
Bob,
You definitely have a wiring problem!
Most likely your bus wiring has a 'bond' between the ground and neutral. Even this shouldn't give a 'significant shock' so you may have more than one problem such as reversed hot and neutral either in the outlet you used or the adapter or cord or bus. But it's almost certain that your bus has, improperly, neutral and ground tied together, probably in the distribution panel.
Regards
Jerry 4107 1120 |
Chuck Newman (Chuck_newman)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 28, 2005 - 10:21 pm: | |
Both! For those that question the significance of the ground wire, this is a textbook example.
Or the necessity of a GFR in the outdoors for that matter.
You received a shock because you became the conductor to ground. You're still alive because typically body contact with dry ground is several megohms resistance. The more resistance, the less current travels through you.
Somewhere in your rig you have a ground fault. It could be in any of numerous places. Take a voltmeter and a long piece of wire and attach the wire to one of the VM leads. Attach the other lead to the frame of the bus/rv. Be sure the voltmeter is on AC volts range. You should see some reading between 30 vac and 120 vac. Have someone in the bus turn off each ac circuit breaker until the voltage goes to zero. The ground fault is somewhere on that circuit. It could be a hot (black) wire touching the ground wire (green or bare), or a grounded metal receptacle box. It could be corrosion allowing current leakage.
Be sure the person at the ac panel wears rubber gloves as the metal face of the panel will be hot also.
This all presumes the rest of the bus wiring is in good shape. Good luck, and be careful.
Chuck Newman
Oroville, CA |
Chuck Newman (Chuck_newman)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 28, 2005 - 10:30 pm: | |
Bob,
I forgot to mention in my post, connect the end of the wire opposite the voltmeter end to a water pipe of other known good ac ground.
For information, neutral to ground bonding on the bus, when pluged into shore power, should not exist as stated above. That said, neutral to ground bond will not give a shock if house and bus ac wiring polarity is correct.
Chuck Newman
Oroville, CA |
Jtng
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 28, 2005 - 10:33 pm: | |
Mm-man:
"I had my unit plugged in with an adapter to fit my shore
power cord to a house 110 outlet. House outlet had no ground
so I used another two prong adapter. "
And with the plug "reversed" in the outlet, the "hot" becomes
the "ground" and vice-versa. Instead of the bus shell being
ground side, it became the hot side. Rather than go crazy
checking the vehicle's wiring, check the polarity of the outlet's
wiring first, to make sure the polarity of the wiring feeding it
is correct. The go buy and install an outlet with a ground.
You should never use a two-pin adapter to feed your RV.
The chance of exactly what happened to you, happens.
While your buying that outlet, pick up one of those simple
outlet testers. You'll need it in the toolbox, anyway. |
Chuck Newman (Chuck_newman)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 28, 2005 - 11:19 pm: | |
John,
Very good point. The only problem is Bob can't check the outlet with a tester simply because the tester requires three wires to work.
You can test the two wire outlet with the DVM using a known good ground, but then it becomes somewhat technical for most people -- particularly when explaining on the board.
I don't know how they get away with still making these two wire adapters. But the ones manufactured in the last decade at least have polarized plugs.
But you're right in checking the source first. I didn't follow my own advice and look at the big picture. But not being there, you go with the information provided.
Chuck Newman
Oroville, CA |
CaSteve
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 28, 2005 - 11:38 pm: | |
EXCELLENT---EXCELLENT---EXCELLENT thread!! There is no telling how many owner/converters were helped by this example of "did it and lived". Thank goodness it was on dry ground. CaSteve |
Brian Brown (Blue_velvet)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 29, 2005 - 3:14 am: | |
You're not alone... I too made the mistake of running my shore cable through a two-prong adapter and shocked myself when camping in my folks' driveway in Texas. Right after the incident, I stuck one probe of my trusty DMV into the dirt and the other onto an aluminum side panel of the bus and it read 115.5v! I was glad it hadn't rained there recently!
After spending some quality time with a DMV, I deduced that the circuit from the panel to the front A/C has a wire shorting to the chassis somewhere. It's all buried in insulation and under paneling, so it will be no small feat to re-run the wire.
Another "did it and lived" story...
Brian Brown
PD4106-1175
Longmont, CO |
Phil Dumpster2
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 29, 2005 - 3:26 am: | |
If all coaches were double insulated, this would never even be an issue.
[ -- Incoming code book thumpers - sheilds up, Scotty!!] |
Chuck Newman (Chuck_newman)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 29, 2005 - 10:50 am: | |
"And with the plug "reversed" in the outlet, the "hot" becomes the "ground" and vice-versa"
Not so. A reversed polarity plug has hot on the neutral wire and neutral on the hot wire. This becomes unsafe with some two wire appliances.
If you have hot on ground, that condition will trip the circuit breaker feeding the affected outlet.
A properly wired bus/rv does NOT have a connection between neutral and ground within the bus, when using shore power. The neutral to ground connection is at the service entrance panel to the residence.
Bob, Jtng is right that the first order of business is to replace the house outlet. After that, I would recommend checking the frame to ground with the DVM. I think you will find a problem similar to Brians.
Chuck Newman
Oroville, CA |
Jtng
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 29, 2005 - 11:54 am: | |
A normal home connects the electric company's ground at the
panel and further secures that ground with a ground rod
placed at close proximity to the home's entrance panel. All
wiring and plumbing should be bonded to that same ground.
With an RV, there is no ground rod, and the actual grounding
will take place at the outlet the RV's shoreline is plugged into.
It should be easy for anyone to understand, that without
properly extending that power supply's ground to your vehicle,
you will be leaving yourself vulnerable to any nuance or
variable of the electrical wiring of either the RV or the power
location supplying it.
There have been many, many cases of mobile homes having
mis-wired hot water heaters, that have caused the metal chassis
and siding to become energized. Proper grounding and bonding
should be of the highest concern. Maintaining proper polarity
between source and use, is equally important.
More simply Bobm, toss out those damned two-pronged crap
before they kill ya'.
. |
Tim Hoskinson (Tdh37514151)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 29, 2005 - 1:33 pm: | |
Hey Chuck I have used a simple outlet tester for over 20 years and it was desinged to tell you if all three conductors were intact as well as telling you which conductors were not present and which ones were cross wired. It also had a spring loaded ground blade tester to let you know if the u blade clasp was getting to loose to safely make ground contact. There are many different types of testers. I think John is on the right track. The problem is more than likely a simple one. Best of luck Bob and be careful |
Jerry Liebler (Jerry_liebler)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 29, 2005 - 10:26 pm: | |
All,
If the bus were wired corectly neither the hot or neutral is connected to the bus frame. No shock regardless of which way the 3 wire to 2 wire adapter is plugged in. This is the major problem, it must be fixed. If this bus doesn't blow the breaker when it's plugged into a properly connected 3 wire outlet then the short is between the neutral and ground in the bus. If it blows the breaker the short is hot to ground.
Regards
Jerry 4107 1120 |
Sean Welsh (Sean)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 30, 2005 - 11:38 am: | |
Bobm,
There is a lot of good information in the foregoing discussion. After wading through all of it, though, I fear that there is maybe too much here to give you a good start on finding your problem.
Taking a different approach, I'd like to suggest the most likely source of your trouble, which is what Jerry just mentioned.
First off, the suggestion that you never, ever defeat the proper grounding when connecting to shore power is a good one. However, you also have a wiring error. I suspect you may never have discovered this error if the coach was grounded (but you may have gotten shocked anyway, albeit a much smaller one).
The most likely problem is an improper ground-to-neutral bond inside your coach. This could be in one of your electrical panels, improper connection of your generator, or even in an appliance.
By code and for safety, there must be no connection anywhere on board between the neutral and ground wiring when you are connected to shore power.
Almost paradoxically, there MUST be such a connection when using an on-board power source, such as a generator or inverter. If you have a system that allows both a shore connection and on board sources (as do most coaches), then you must have a mechanism which automatically implements the bond when not connected to a shore source, and breaks the bond when connected to a shore source.
If, as I suspect, you have an improper connection between ground and neutral on board, then there need be no other wiring error to cause the symptom you described. Any 120v appliance or lamp that is "on" will be returning its current via both the frame and the neutral wiring, effectively making the entire frame of the coach "hot." When you touch the coach, you become part of the return path. How much current will flow through you depends on how much resistance you present, versus how much resistance the neutral return path back to the panel presents. The neutral is a fairly small wire, and could be running hundreds of feet before it is bonded to ground.
Having the ground wire properly connected would tend to divert any current flowing through the frame more directly to ground, and so the effects of the hot frame would be less noticable.
This is a potentially dangerous condition even if you always use a proper ground connection, so I strongly recommend that you track down the erroneous connection and repair it.
-Sean |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 30, 2005 - 11:54 pm: | |
Sean-
A question for you...
With the older 30 amp RVs, the electric was a split system.
When you ran the genset, it would power both air conditioners,
but when on shore power, only one would work. The other
"1/2" of the system remained connected to the genset circuit.
If you were connected at a power pole and wanted to run the
other 1/2 of your RV, you could start the genset and power
it, from that.
Since that was the customary wiring for nearly all older 30amp
RVs, isn't it in direct conflict with the wiring codes? And there
is no remedy for that, since both genset and shore power are
(can be) serving the same RV at the same time.
Bobm didn't tell us what type of vehicle he has, or if it was
wired for 30 or 50amp service, nor did he tell us if it was
wired in the manner all older RVs were wired.
Wouldn't he be chasing his tail, if he's instructed to locate a
"fault", when the wiring meets all practical methods of service
as it had been; never before, considered "a fault" by the industry?
Kinda' curious.... |
Sean Welsh (Sean)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 01, 2005 - 11:03 am: | |
JTNG,
Your supposition about how those coaches were wired is incorrect. There is no code violation involved.
In that system, the generator has it's own internal ground/neutral bond, as required by code.
There is a junction box for the generator wiring. From that j-box, one set of wires runs to one of the AC's, and one set of wires runs to either a 30-amp receptacle, or a transfer switch.
The main 120v electrical system terminates either in a shore cord, or at the transfer switch. If a transfer switch is used, it transfers both hot and neutral.
When the shore cord is connected, the neutral of the main system is connected to shore power, and the ground bond is in the shore system. The second AC, however, is connected directly to the generator, and it's ground/neutral bond is in the generator.
The neutral of the main system is not connected to the coach frame. The main system, running from shore power, and the second AC, running from the generator, are "separately derived systems" under the code. Their neutrals are not interconnected.
Bobm has a wiring fault.
-Sean |
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