Adam-12 wrote:
As far as wiring damage and someone mentioned "polarity," ha! Good luck on a "polarity" issue. Outlets in America run "AC" current, so "polarity" is a moot topic of discussion.
Actually, IMHO "polarity" is a huge topic of discussion. See my article at
RPBG and video at
RPBG VideoWhile a simple polarity reversal of a H-N swap shouldn't be dangerous if the RV's electrical system has a properly isolated Ground and Neutral, homes, garages, office buildings, and campgrounds originally wired prior to the early 70's often had no safety ground wire at all. In an mis-guided effort to provide grounded outlets, some electricians and DIY guys in the 80's (and as late as 2012 that I know of) would do something called a "bootleg ground" by connecting a jumper wire between the Ground and Neutral Screws on the outlet itself. While a violation of the NFPA National Electrical Code, if the Hot/Neutral polarity was properly observed, then there was no immediate danger. However, if a bootleg ground is combined with a reversed polarity, then you have something I call a Reverse Polarity Bootleg Ground (or RPBG). As you'll see in the linked article and video, an RPBG cannot be detected by a 3-light tester or even a voltmeter testing H-N, H-G and G-N for proper voltages. The only way to detect an RPBG is to meter between the outlet safety-ground and earth-ground (ground rod) or by using a Non Contact Voltage Tester (NCVT) that will trigger on potential over 40 volts AC.
An RPBG creates a very dangerous condition since the appliance or RV will appear to operate normally, but its chassis/skin will be at a full 120-volts above earth potential. Anyone touching the chassis and a ground (damp earth) at the same time will be shocked and potentially electrocuted. While almost impossible to occur with modern wiring, I believe that RPBGs are fairly common in old garage outlets, churches, and houses that were improperly "upgraded" to grounded outlets in the 80's. And since anything plugged into them will appear to operate normally, even for decades, it just takes the right combination of circumstances to become lethal.
Interestingly, none of the major test equipment manufacturers (Amprobe, Ideal, Fluke, etc...) seem to know about this, and I've spent the last year talking to their engineering departments and having them duplicate my RPBG experiment. All of them agree that it's a real problem that can't be detected by normal testing methods. I went through this most recently with Progressive Industries who told one of my NoShockZone readers that their devices would detect and protect RVs from an RPBG. But after I convinced PI to mock up the test for themselves, they called me back to acknowledge that there are no surge or voltage protector devices on the market that will detect or protect you from an RPBG, even their own products.
As far as the note on 480 volts, it's true that you won't normally find it at a campground. But in a conversation with PI they noted that a competitor's 120-volt product would often blow up if accidentally connected to 240 volts, while their devices are tested to 480 volts. Since a lot of Progressive Industry products are used in industrial situations and oil fields, there have been instances where they've been accidentally connected to a 480-volt, 3-phase feed, which is very common in those situations. When connected to 480-volts, it did exactly what it was designed to do, stop the voltage from getting to the RV electrical system while not being destroyed. That's a great testimony to the engineering of Progressive Industry products.
Mike Sokol
mike@noshockzone.org
www.noshockzone.org
