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Author Topic: Hot and Neutral swapped.  (Read 14081 times)

Jeffery Foster

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Re: Hot and Neutral swapped.
« Reply #10 on: September 18, 2014, 06:34:41 pm »

But neither a standard bootleg ground or RPBG can be found with a standard outlet test,
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Those 3-light cube testers will lead you astray in a hurry, so you need to do an actual metered voltage test against a known ground to be sure of what's happening.

Hopefully without derailing the thread, can you explain this procedure? Is this something that should be checked for when we arrive at each new venue (beyond the typically voltage metering)?
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Mike Sokol

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Re: Hot and Neutral swapped.
« Reply #11 on: September 18, 2014, 06:48:04 pm »

Hopefully without derailing the thread, can you explain this procedure? Is this something that should be checked for when we arrive at each new venue (beyond the typically voltage metering)?

I am actually writing a book about this, but I'll see if I can come up with a quick pre-show voltage checklist that should identify all dangerous faults. I'll be counting on the senior/pro contributors to help me edit this a bit so it's safe for all situations. But I do think it's an important function of this forum. 
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John Roberts {JR}

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Re: Hot and Neutral swapped.
« Reply #12 on: September 18, 2014, 06:58:10 pm »

Hopefully without derailing the thread, can you explain this procedure? Is this something that should be checked for when we arrive at each new venue (beyond the typically voltage metering)?
I look forward to Mike's book, but maybe do a search Mike has discussed this before.

JR
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TJ (Tom) Cornish

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Re: Hot and Neutral swapped.
« Reply #13 on: September 18, 2014, 08:44:07 pm »

Hopefully without derailing the thread, can you explain this procedure? Is this something that should be checked for when we arrive at each new venue (beyond the typically voltage metering)?
I'm not Mike and this procedure doesn't cover every base fully, but this would be a good start:
http://tjcornish.com/articles/receptacle-testing.html

The issue with reverse polarity bootleg stuff is that unless you have an external reference, most testers can be fooled.  The only way to ensure that you don't have a RPBG are to measure from the ground of the receptacle under test to a known ground such as a water pipe, conduit, or even the actual earth and make sure you're not reading line voltage. 

Though not as reliable as a direct measurement to known earth, Mike has written earlier about using a non-contact voltage tester as an indicator.  A RPBG will cause the non-contact tester to light up over a larger area than normally happens with a correctly wired receptacle.  A search of Mike's NoShockZone.org site should bring up the procedure, or else I'm sure he'll link it here.
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Mike Sokol

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Re: Hot and Neutral swapped.
« Reply #14 on: September 18, 2014, 09:58:46 pm »

Though not as reliable as a direct measurement to known earth, Mike has written earlier about using a non-contact voltage tester as an indicator.  A RPBG will cause the non-contact tester to light up over a larger area than normally happens with a correctly wired receptacle. 

Here's my most complete article on using a Non Contact Voltage Tester to check for a hot ground caused by an RPBG. http://ecmweb.com/contractor/failures-outlet-testing-exposed A NCVT will also find a hot-chassis backline amp or guitar with at least 40 volts on it. Since a floating ground may allow the chassis potential to float up to around 1/2 of the line voltage, you can easily detect it. That's because a standard sensitivity (90 to 1,000 volt) NCVT will beep/blink at around 40 volts when held close to any large electrified surface. In fact, it will beep/blink as far as 2 feet away from something as large as an RV with 120 volts potential on the chassis and skin. See a video of me testing for a hot-skin on a 40-ft RV at http://www.youtube.com/watch?v=Y8h64X33aKg
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Mike Sokol

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Re: Hot and Neutral swapped.
« Reply #15 on: September 18, 2014, 10:10:25 pm »

I'm not Mike and this procedure doesn't cover every base fully, but this would be a good start:
http://tjcornish.com/articles/receptacle-testing.html

TJ, I would say this is a VERY good start for basic receptacle testing before plugging in. If you add a quick check with a NCVT for a hot ground, that would also find any RPBG mis-wiring conditions.

Those N-G swapped receptacles can be really hard to sort out, but once you find them that can explain all sorts of ground loop hums that change under load.
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Kevin Maxwell

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Re: Hot and Neutral swapped.
« Reply #16 on: September 19, 2014, 09:46:49 am »

I got a call back this morning from the property manager and I explained the situation to her and she is going to call in an electrician to check it out. I would love to know exactly what they find. 
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Mike Sokol

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Re: Hot and Neutral swapped.
« Reply #17 on: September 19, 2014, 09:57:37 am »

I got a call back this morning from the property manager and I explained the situation to her and she is going to call in an electrician to check it out. I would love to know exactly what they find.

Please ask her if the electrician can contact me with a report on what they found. This is important information for all of us. They can email me at mike@noshockzone.org
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Steve M Smith

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Re: Hot and Neutral swapped.
« Reply #18 on: September 19, 2014, 09:58:49 am »

I am always amazed by the variety of faults I read about here in US power systems.  I have never found a swapped ground and neutral here in the UK and in thirty years, I have only found a swapped live and neutral once - and that was in a temporary installation.


Steve.
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Kevin Maxwell

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Re: Hot and Neutral swapped.
« Reply #19 on: September 19, 2014, 10:12:06 am »

Please ask her if the electrician can contact me with a report on what they found. This is important information for all of us. They can email me at mike@noshockzone.org

I know these people well enough that the only way I will find out anything is if I am there with the electrician and see what the issue is myself. And it would have to be off the clock. I now have a number to text her at and I may ask if I can tag along and see what is discovered. I am slow right now and may do that.
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ProSoundWeb Community

Re: Hot and Neutral swapped.
« Reply #19 on: September 19, 2014, 10:12:06 am »


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