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Author Topic: Is it just me or is there some really dangerous stuff going on here...  (Read 6632 times)

Mike Sokol

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Re: Is it just me or is there some really dangerous stuff going on here...
« Reply #20 on: March 13, 2014, 12:14:23 pm »

I am not sure of the purpose for not bonding the neutral to ground.  A 3-5K genny is plenty to run multiple pieces of   equipment, and if you are using a drill with a grounded case that shorts hot to the case, you now have energized the genny with no path to trip OCPD. 

There's an exception in the code which allows for portable/contractor generators under 5KW to not require GFCI protection if they have a floated neutral. I think this was originally added to avoid GFCI nuisance tripping at work sites, but has since been adopted for all small portable generator situations. The second reason for the floated neutral (at least from my discussion with Honda tech support) was that if you used your little 2KW generator to power your entire house during a power outage via a transfer switch, then the house circuit panel would provide the G-N bond, and a second G-N bond inside the generator was a code violation. Of course, that secondary G-N bond would also trip any GFCI in the path during safe use. So while that's true, very few small generators are tied into a house circuit panel via a generator transfer switch. The flip side of this is that many contractor generators OVER 5KW already have an internal bonded neutral, which makes it a code violation to tie it into your house panel via a transfer switch. Yikes!  >:(

This little bit of intel took me a long time to gather simply because of the confusing and incorrect use of words such as grounding, safety-ground, bonding, earth-grounding, etc...   If you note, I use the term G-N-E bonding when discussing circuit panels because that's where the neutral bus, safety-ground bus, and ground-rod all come together physically and electrically (or at least they're SUPPOSED to).
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Mike Sokol
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Stephen Swaffer

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Re: Is it just me or is there some really dangerous stuff going on here...
« Reply #21 on: March 13, 2014, 04:03:11 pm »

I have installed quite a few generator transfer switches set up for 4kw to 7kw generators-have to love that 5 kw break they put in there!  Pretty common here (rural Iowa)-a few years back we lost power for 4 days-no heat and no well pump makes for conditions that really aren't intolerable-but "we" have been accustomed to such comforts! 

I understand the second bond is a code violation-but to me it would seem to be a less serious issue than a missing bond but what do I know?  It also seems really odd that all outdoor recpts have to be GFCI, as well as all outlets used  during construction have to be GFCI-but a generator, which you can not safely run indoors does not need to be GFCI.  Must be nice to not have to be reasonable!
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TJ (Tom) Cornish

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Re: Is it just me or is there some really dangerous stuff going on here...
« Reply #22 on: March 13, 2014, 04:06:16 pm »

I have installed quite a few generator transfer switches set up for 4kw to 7kw generators-have to love that 5 kw break they put in there!  Pretty common here (rural Iowa)-a few years back we lost power for 4 days-no heat and no well pump makes for conditions that really aren't intolerable-but "we" have been accustomed to such comforts! 

I understand the second bond is a code violation-but to me it would seem to be a less serious issue than a missing bond but what do I know?  It also seems really odd that all outdoor recpts have to be GFCI, as well as all outlets used  during construction have to be GFCI-but a generator, which you can not safely run indoors does not need to be GFCI.  Must be nice to not have to be reasonable!
NEC2014 requires all "user accessible" receptacles to be GFCI if there is the possibility of multiple circuits - i.e. 240v operation.  In the case of a single circuit floating generator, there's no circuit for the fault current to go to that would trip the GFCI.
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Kevin Graf

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Re: Is it just me or is there some really dangerous stuff going on here...
« Reply #23 on: March 13, 2014, 09:22:58 pm »

Getting back to the RemyRAD character. It would appear that he is using a Signal Transformer Model DU-7.5, 7.5 KVA Power Isolation Transformer.  When he speaks of  3 phase power, he is only using one phase and stepping 208V down to 120V.

http://www.signaltransformer.com/home/step-updown-power-isolation/
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Greg_Cameron

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Re: Is it just me or is there some really dangerous stuff going on here...
« Reply #24 on: March 13, 2014, 09:29:47 pm »

Getting back to the RemyRAD character. It would appear that he is using a Signal Transformer Model DU-7.5, 7.5 KVA Power Isolation Transformer.  When he speaks of  3 phase power, he is only using one phase and stepping 208V down to 120V.

http://www.signaltransformer.com/home/step-updown-power-isolation/

It also seems Remy is saying the there is no neutral ground bond on the secondary side of that transformer either in the transformer or load center. If that's the case, that could be very dangerous. Waiting for clarification on that one.
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Mike Sokol

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Re: Is it just me or is there some really dangerous stuff going on here...
« Reply #25 on: March 13, 2014, 09:48:28 pm »

It also seems Remy is saying the there is no neutral ground bond on the secondary side of that transformer either in the transformer or load center. If that's the case, that could be very dangerous. Waiting for clarification on that one.

That's what the link suggested, a totally floating secondary on the iso transformer with no connection to the PoCo neutral or ground connections. And I agree that it's a very dangerous situation. 
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Stephen Swaffer

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Re: Is it just me or is there some really dangerous stuff going on here...
« Reply #26 on: March 14, 2014, 11:46:17 am »

That's what the link suggested, a totally floating secondary on the iso transformer with no connection to the PoCo neutral or ground connections. And I agree that it's a very dangerous situation.

NEC 250.21 Lists AC systems that need not be grounded.  Audio/Video equipment did not make the list. 250 .20.B requires a grounded system anytime you are working with 120/208/240 systems with a common conductor if you are supplying any type of distro.
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Mike Sokol

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Re: Is it just me or is there some really dangerous stuff going on here...
« Reply #27 on: March 14, 2014, 12:26:32 pm »

NEC 250.21 Lists AC systems that need not be grounded.  Audio/Video equipment did not make the list. 250 .20.B requires a grounded system anytime you are working with 120/208/240 systems with a common conductor if you are supplying any type of distro.

The only isolated power I worked with was for very specific test gear (we were building and measuring R2R ladders for missile guidance systems) and there were all kinds of safeguards in place. And even these isolated power systems had their own ground rods that were kept completely separate from the PoCo ground and any building steel. We were required to do regular measurements on the isolation transformer as well as our isolated ground rod as part of our measurement SOP.

None of this isolated power is safe or relevant for any type of AV system, and a violation of code.   
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Mike Sokol
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