Outlet Testing - DANGER

[Optimistic Paranoid]

Here’s something I only came across recently.

Did you know that in one particular circumstance, those little three light outlet testers can lie to you and tell you that it’s safe to plug in to an outlet when in fact it’s not safe at all?

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Mike Sokol is an electrical engineer, and his website:

The No Shock Zone

is full of interesting electrical info for RVers.

Regards
John

 

[GotSmart]

That is great information!

 

[jmsokol]

That is great information!

Thanks for posting my No~Shock~Zone info on this forum. Here's a link to the full article I wrote about RPBGs (Reverse Polarity Bootleg Grounds) for electricians http://ecmweb.com/contractor/failures-outlet-testing-exposed and here's a link specifically about RPBG failures as they relate to campers and trailers of all types. http://www.rvdoctor.com/2001/07/friends-of-gary-mike.html

Let me know if you have any questions about electrical safety.

Mike Sokol
[email protected]
www.noshockzone.org

 

[highdesertranger]

lots of good info here. I use both the plugin testers and the non contact testers for my apartment maintenance job. also a dvm. highdesertranger

 

[rvpopeye]

Mike Sokol is an old road dog sound system tech like me. You really need to know your stuff in that job.
His No Shock Zone series is great info in an easy to understand form , following his advise can save your A$$ !

 

[jmsokol]

Doing electrical checkout on a bunch of apartments in a new BOQ at the local Navy Base I got an oddball readout on the little three light tester. Further testing with the volt meter revealed that there was 208 volts on the receptacle, each side had 120 volts to ground. Took an hour to sort it out. Even people that are being paid good money to know what they are doing screw up sometimes so be careful.

Guy

I'll bet they tied into something called a high-leg Delta service. I've encountered that a number of times in older converted industrial buildings that used a lot of 3-phase motors. Also called a Red-Leg or Wild-Leg service, two of the three phases will measure 120-volts to neutral, but the third "High Leg" phase will read 208 volts to neutral. See this link for an overview: http://en.wikipedia.org/wiki/High-leg_delta

I heard about this being accidentally done to the 30-amp pedestals at a campground for their recently expanded campsites. The electrican wiring up the new feeds saw a row of unused circuit breakers on the 3-phase panel, and simply wired up a bunch of the new pedestals without metering anything. Several campers had plugged their shore power lines into these new pedestals and were burning up their RV electrical systems. When they complained to the campground operator, he told them they must have had a lightning strike. Finally one smart camper metered the receptacle as you did and discovered the 208 volts on the 120-volt TT-30 outlet. First of all, you should meter all unknown outlets before you plug in. But every electrician should certainly meter every service panel and receptacle for the correct voltage before and after doing any electrical work. Don't get me started on problems with grounds and bonding. I work with electricians all the time who don't understand the differences or how to diagnose incorrectly grounded and bonded boxes in the field.

And yes, I'm proud to be recognized as a road dog sound technician. That gig allows me to see hundreds of different electrical systems every year and lots of crazy wiring. But I'm also and Master Electrician as well as a Mechanical/Electrical engineer and used to be a robotics designer control designer as well as building and calibrating nuclear missile guidance systems. That's why I find campground power fascinating and keep designed new electrical testing methods to make it safer.

Let's play safe out there...

Mike Sokol
www.NoShockZone.org
[email protected]

 

[jmsokol]

Oops... Double post.

 

[rvpopeye]

Hey Mike , good to see you on another forum helping folks to keep from letting the magic smoke out of themselves !