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Important - check this every time you set up

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Tars Tarkas View Drop Down
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Post Options Post Options   Quote Tars Tarkas Quote  Post ReplyReply Direct Link To This Post Topic: Important - check this every time you set up
    Posted: 22 May 2014 at 7:51pm
An additional fun feature of these testers is that when you have them on while driving under high voltage electric lines -- the kind that run from tower to tower rather than pole to pole -- they will light up and beep.

TT
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Post Options Post Options   Quote jmsokol Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 2014 at 8:38pm
Originally posted by Tars Tarkas

An additional fun feature of these testers is that when you have them on while driving under high voltage electric lines -- the kind that run from tower to tower rather than pole to pole -- they will light up and beep.

TT


True, and that's because your body or vehicle is actually elevated to several thousand volts above earth potential while standing under power lines. No kidding. In fact, if you park your tow vehicle and RV directly under high-tension power lines (yup, those big ones) you can get a pretty good shock while standing on the ground in bare feet or wet shoes and touching the door handle. I've discussed this phenomenon with a number of Power Company Engineers who say that the current is supposed to be less than 5 mA at the normal 14 ft minimum wire distance to ground suggested by the utilities. However, since that power line could have up to 500,000 volts on it (yup, half-a-million volts), then you could get up to 10,000 volts bias on your vehicle (but at less than 5 mA current). So while the shock could startle you, it shouldn't be dangerous. I'm going to do an experiment this summer showing how a car spark plug attached to the bumper of an RV will spark continuously when connected to a ground rod. Too much fun...

Interesting stuff, eh?
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Post Options Post Options   Quote techntrek Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 2014 at 10:04pm
Interesting info in your 2nd to last post.  Sounds like that would explain why the voltage between chassis and ground dropped as I turned off each breaker on the converter, and why I never could figure out what was "wrong".  I verified the wiring on the TT-30 outlet and the end of the cord (L5-30) connected to the camper both are right (lower-left to the ground pin is hot), and the ground to chassis looked good.

I've read of high tension line voltages higher than 500,000, both AC and DC.  I think 765k is one popular voltage.  I've seen demos where a fluorescent tube can be lit while standing under them, similar to a Tesla coil.  Amazing the voltage differential can be so great, I never knew you could get an actual shock.  Yes, this stuff is interesting/fun for me.  Cool
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Post Options Post Options   Quote Cap-n-Cray Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 2014 at 11:30pm
Would a surge suppressor have any effect in this situation?
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Post Options Post Options   Quote jmsokol Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2014 at 12:36am
Originally posted by Cap-n-Cray

Would a surge suppressor have any effect in this situation?

There are basically two types of surge suppressors on the market. One is a surge-only type with MOV devices that will stop voltage spikes from the power line. These cost around $100 but will do nothing to prevent hot-skin shock from an open-ground situation. The second type is a voltage-monitor/suppressor type with a relay that will disconnect your RV from the power line if the ground is open or the voltage goes above or below preset limits. This should protect you from an open-ground condition at the pedestal, but not when Cost is between $200 to $300 for a 30-amp model. See my No~Shock~Zone article at http://www.noshockzone.org/rv-electrical-safety-surge-strips/

However, note that neither of these products will detect or disconnect you from a very dangerous mis-wiring situation I call a Reverse Polarity Bootleg Ground (or RPBG). An RPBG occurs with a DIY guy or old-school electrician added grounded outlets to old (pre-1970's) wiring by adding a jumper between the Neutral and Ground screws rather than running a new grounded wire. If the Hot-Neutral polarity is correct, then this creates a normal Bootleg Ground, which is a code violation but not immediately dangerous. However, if the Hot and Neutral "polarity" is reversed somewhere in the walls or conduit, then the Hot contact is now at 0 volts, while the Neutral and Ground are both at 120-volts. Anything you plug into an RPBG outlet will operate normally, except that the chassis is now at 120-volts with full circuit breaker amperage available. And there is NO tester on the market that will find an RPBG. See my articles at the RV Doctor's website at http://www.rvdoctor.com/2001/07/friends-of-gary-mike.html or in EC&M magazine where I bring the RPBG situation to the attention of the electrical contracting industry:
http://ecmweb.com/contractor/failures-outlet-testing-exposed

Note that a basic Non Contact Voltage Tester will easily find an RPBG mis-wired outlet in seconds, both before and after plugging in your RV power cord.
 
Where do you find RPBG outlets? Certainly not in new campgrounds with proper wiring. But I've heard reports of them in very old campgrounds and boat docks that never ran new wiring when upgrading to grounded outlets. And I've personally seen them in a number of home garages as well as pre 70's church wiring that's been upgraded to grounded outlets by well-meaning or misinformed "electricians", some of whom are actually licensed. So be very careful when parking your RV in your buddy's driveway and plugging into "garage" power. That seems to be where RPBG outlets happen the most.
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Post Options Post Options   Quote techntrek Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2014 at 8:18am
Worth repeating in short form, so nobody misses it.  

Even if you have an advanced surge/monitor installed in your camper (or the plug-in version outside), you still need to get a VoltAlert or one of the other models Mike listed previously.

You've spent more than $30 on other camping gadgets, and few of those gadgets can save your life like this one can.

BTW, I've added this topic to the "R-pod manual" thread.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Post Options Post Options   Quote fwunder Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2014 at 8:24am
This is a great thread. I ordered my Volt-Alert this morning.

One has to wonder why a Hot-Skin alarm system isn't built in as a standard.

Thank you very much for this information!

fred
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Post Options Post Options   Quote techntrek Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2014 at 8:41am
Good question.  It wouldn't cost more than the already-required LPG/smoke/CO detectors.  Only catch is it would only work while you had a firm grip on it, while standing on the ground outside.  Two possible solutions - add a large touch pad just above the power connection so you could plug in, press your hand to the pad and get a read-out just above it.  And/or redesign the door handle so it is insulated, and every time you grab it you get a readout above the handle.  There are issues - would it work if the sensor was wet or had road grime on it, what if you are using a plastic step-stool in front of the door, etc.  But there are solutions - put the sensor inside a cover, and maybe only putting it above the power connector is the better location even though it would only get checked once and not every time you get in the camper.

I could see a market for this, but it would take a ton of public education to generate the demand.  Manufacturers wouldn't add it to their campers unless forced by regulations or high market demand.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Post Options Post Options   Quote jmsokol Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2014 at 10:05am
Actually, there's a pretty easy way to manufacture a built in hot-skin detector (which I've already built and tested). However, it seems like the RVIA and RVDA are not interested in promoting that an RV can become a shock hazard if plugged into a mis-wired outlet or extension cord. Their point of view is that it might scare prospective buyers away from purchasing new RVs. No kidding, I've sat at a desk in front of these guys and asked them about it point-blank. I also had an off-the-record comment from an RV industry official who stated that having an RV's electrical system destroyed by improper voltage hookup was not necessarily a bad thing since now the insurance company would pay to install a new refrigerator, inveter/converter, HVAC, etc... and that RV suppliers would thus be selling more replacement parts. The potential for loss of life from a hot-skin shock wasn't even on their radar.

So yes, while I believe that consumer education about electrical safety is the key to safe RVing, I seriously doubt that the RV industry will fund it unless there's a big push from consumers to do so. That's why I spend so much time developing demonstrations and testing techniques for RV owners. This is not my day job... I'm actually a technology instructor who teaches live music production around the country. I've been pitching the idea of RV consumer and technician electrical safety training for the last several years to the RV Industry, but without any traction. So if you think this is important then please contact your RV manufacturer representative and ask them to support No~Shock~Zone seminars at your rally or RV sales event. I'm already driving around the country teaching my live-sound classes and could also schedule single-day No~Shock~Zone clinics at dozens of RV events every year. But the push has to come from those purchasing new RVs, as that's the only group they'll listen to. You all have my NSZ contact info and links to my articles and videos, so please pass it on to them and tell them you consider this to be an important topic.

Thanks for your interest and support. Keep those questions about electrical safety coming.
    
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Post Options Post Options   Quote outermostpod Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2014 at 10:27am
Just ordered the VoltAlert from Amazon.  Got one for my Father-in-law too.  For $30 bucks it is not worth the risk. Just add it to the checklist of stuff to do when you set up camp.

Thanks for bringing this to our attention. I would have never known.
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