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Author Topic: Ground loop with a portable generator  (Read 1476 times)

Phil Graham

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Re: Ground loop with a portable generator
« Reply #10 on: September 22, 2017, 03:45:16 pm »

Not sure what panel you are installing.  Several manufacturers make UL listed kits to allow a breaker in the panel to be interlocked with the main and backfed to be used as a transfer switch.  This is usually far more cost effective than a seperate transfer switch and very easy to incorporate during an upgrade like this.  I've installed several and never had an inspector have an issue.  Just an option to explore.

Stephen,

You have links to some of those?
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Stephen Swaffer

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Re: Ground loop with a portable generator
« Reply #11 on: September 22, 2017, 04:50:34 pm »

https://www.amazon.com/s/?ie=UTF8&keywords=interlock+kit+square+d&tag=mh0b-20&index=aps&hvadid=77653035794143&hvqmt=b&hvbmt=bb&hvdev=c&ref=pd_sl_8l6i84nkwj_b

http://www.milbankworks.com/specsheets/784572478787_SS.pdf


They are panel specific so just search your manufacturer-I've preferrred Sqyare D panels-they are available at bog box retailers as well.  The Milbank works in their meter/main panel setup-if your POCO allows their models I really like those-they let you setup connection to your genny outside the house-and often in an old install they run service entrance conductors too far through the house for new inspections so it fixes that non-compliance as well.

The other thing I usually do is instead of an inlet, I hard wire a male plug to a piece of SO and coil it up inside a 12"X12" 3R jbox outside.  Most people would only use the 4 wire cable with their genny for emergency power to their house - this is usually a little cheaper than an inlet and you'll never misplace the power cord for your house.  All you'll need in a power outage is the genny and a screwdriver.
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Steve Swaffer

Steven Cohen

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Re: Ground loop with a portable generator
« Reply #12 on: September 23, 2017, 10:37:13 am »

Thanks Stephen for the response.

 You correct in stating that I was referring to using the manufacturer supplied ground screw on the generator connected to a copper ground wire that runs between my pool pump and AC. I was not planning on making any type of internal modification or ground to neutral adapter.

 My original plan was to output the 30 amp/125volt, twist lock receptacle on the generator, connecting a 100 foot, 10/3, GenTran cord with a quad box. Each duplex on the quad box has its own 20 amp breaker. Here is a link to a 25 foot version of the same setup.

https://www.amazon.com/gentran-generator-contractor-receptacles-b10325dw/dp/b001ulbrn2


 For clarity, my original concern was that I would have potentially two paths to ground, one being the known ground of the connection between the ground screw on the generator and the copper bond between my AC and pool pump, and the potential ground of the security chain wrapped around the metal handle of the generator and the other end of the security chain wrapped around an aluminum fence. I was not sure if having two paths to ground, if the aluminum fence is grounded, was unsafe.

I am still a bit unclear if I ground the floating neutral inverter generator using the ground screw connected to a copper ground is unsafe. That is the reason why I am now looking into a manual transfer switch when I have the new electrical service panels installed. I am not sure if an interlock will work because I have my main breaker on one panel outside near the meter, and a sub panel in the garage for the rest of the house, I will ask the electrician if this is an option.

Another issue I will face if I connect the generator to the main service panel is that the main panel is in the front of the townhouse. I want to keep the generator at the rear of the townhouse so it is out of plain view. The townhouse is two floors and connected on both sides. It will be a difficult, expensive run. That is why I originally opted for the single GenTran extension cord with a quad box. But if I cannot ensure that it is as safe as connection to the service panel, the expense is worth the costs.

Thanks again to everyone who has responded with suggestions,
Steve
 

         

My understanding is that he was using the ground screw on the genny-which is essentially the frame of the genny to bond to the fence/egc.  This has absolutely NOTHING to do with ground-neutral bonding-which on that genny could only be accomplished by an internal modification or some sort of a G-N adapter as has been discussed in other threads.  Making sure the fence is in fact bonded to the install (not just earth grounded) adds a significant measure of safety to this setup-even if the genny is connected through a transfer switch and thus bonded to ground.  There was a recent electrocution (Kansas, I believe) of a child that in all liklihood would have been prevented had the fence been bonded to the electrical service (no matter if that is a genny or mains).

I would argue that a GFCI still provides protection in the case of a double fault.  Sure-it won't detect current flowing from line-line.  GFCI's never will, but if fault current takes an  alternate path bypassing any part of the proper circuit of a GFCI it will still trip.  If there is no path for fault current to follow to trip the GFCI, then there is no path for fault current to follow to electrocute somebody.  I'd rather have the GFCI present in case a fault occurs that I am not aware of-either in the genny or something attached to the genny-that essentially bonds one side of the circuit making it a "neutral".

Stephen,

Not sure what panel you are installing.  Several manufacturers make UL listed kits to allow a breaker in the panel to be interlocked with the main and backfed to be used as a transfer switch.  This is usually far more cost effective than a seperate transfer switch and very easy to incorporate during an upgrade like this.  I've installed several and never had an inspector have an issue.  Just an option to explore.
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Rob Spence

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Re: Ground loop with a portable generator
« Reply #13 on: September 23, 2017, 02:51:14 pm »

This comment only applies to using the generator stand alone.

If using the generator with the quad box you linked to, the security chain to the fence will be fine. The ground wire from the pool will be the safety ground.

However, to make faults to ground trip the circuit breaker, you need to bond the neutral to ground. The easy way, as described by Mike Sokol, is to take a common Nema 5-15 cord cap, wire the neutral screw to the ground screw, paint it an awful color, and plug it into a receptacle on the generator.

Note, the shorting plug should not be used when connecting to a home breaker panel as the main panel will (should?) have bonded the neutral to the ground (per NEC) and you only want that bonding done in one place.


Sent from my iPad using Tapatalk HD
« Last Edit: September 23, 2017, 02:53:25 pm by Rob Spence »
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Stephen Swaffer

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Re: Ground loop with a portable generator
« Reply #14 on: September 23, 2017, 04:40:58 pm »

Thanks Stephen for the response.



https://www.amazon.com/gentran-generator-contractor-receptacles-b10325dw/dp/b001ulbrn2


 For clarity, my original concern was that I would have potentially two paths to ground, one being the known ground of the connection between the ground screw on the generator and the copper bond between my AC and pool pump, and the potential ground of the security chain wrapped around the metal handle of the generator and the other end of the security chain wrapped around an aluminum fence. I was not sure if having two paths to ground, if the aluminum fence is grounded, was unsafe.


To this specific question.  The NEC requires any and all "grounding electrodes" present on a premises to be bonded (connected with a metalic path).  Obviously, if multiple paths to ground were an issue that would not be required.  It is common to have ground rods, metal water lines, gas lines and ufer (concrete encased electrodes-usually the rebar of a foundation) all connected in building.  I just finished a large inustrial addition with a separate service than the original building-both steel frame buildings.  For safety purposes we intentionally bonded the frames of both buildings.  There are a LOT of paths to ground in this structure.

In addition, code requires anything metallic that "may" become energized to be bonded to that system-ie a fence that has a power cord run through, over, or near it.

Guys service hi tension lines while energized by wearing a metallic "farady" cage style suite.  The idea is that in a suit like that no part of their body can be energized to a different part than any other.  That is the same idea as bonding metal parts and grounding electrodes (either intentional or incidental) together to create one big metal "cage" of anything metal on a premises.  Your concern of the chain wrapped around the fence and genny without an intentional bond is a perfect example of hazards people often overlook-you were wise to see that as a hazard-I would suggest ensuring that is in fact bonded somehow.

Others have spoken correctly on the ground-neutral bond.  This specific connection should exist for safety-and it should exist in only one place.  Multiple G-N bonds will create undesired, unsafe loops.
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Steve Swaffer

Phil Graham

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Re: Ground loop with a portable generator
« Reply #15 on: September 24, 2017, 12:54:44 pm »

...I was referring to using the manufacturer supplied ground screw on the generator connected to a copper ground wire that runs between my pool pump and AC. I was not planning on making any type of internal modification or ground to neutral adapter.

 My original plan was to output the 30 amp/125volt, twist lock receptacle on the generator, connecting a 100 foot, 10/3, GenTran cord with a quad box. Each duplex on the quad box has its own 20 amp breaker...

Steve,

Kudos for asking questions. You've inadvertently stepped into a tricky world. Floating neutrals are 'magically' safe and code compliant for their two most common use cases for Joe public:

1. "Cord and plug connected" equipment (e.g. power tools, emergency refrigerator) with no connection to earth. This is safe because there is no fault current path, and is code compliant as per NEC 250.34.

2. Tied to a house panel via transfer switch for backup power. Here the panel provides the neutral -> ground bond, and the floating neutral insures that there aren't two parallel paths to the generator over neutral and EGC, as required by NEC 250.6.

As Stephen has explained, many points of bonding between ground rods and GEC is common, preferred, and to code. Ground to ground is good.

The problem arises when there are multiple neutral -> ground bond points, which can cause the EGC, which is normally not a current carrying conductor, to be a parallel path for the return current to the generator.

Quote
I am still a bit unclear if I ground the floating neutral inverter generator using the ground screw connected to a copper ground is unsafe.

If you are going to bond the generator to your pool GEC, and then use outlets connected via cord and plug, you should create a N -> G bond on the generator in the manner that Rob describes in this thread.

If you are going to use the Yamaha with a transfer switch, then the N -> G bond will be in the panel and the generator is ready to go without any additional bonding.
« Last Edit: September 24, 2017, 02:16:32 pm by Phil Graham »
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Steven Cohen

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Re: Ground loop with a portable generator
« Reply #16 on: September 24, 2017, 07:34:30 pm »

Thanks everyone for the information.

Today I made a neutral to ground NEMA 5-15 plug. I will use that plug, along with bonding the generator to the ground wire that runs between my AC and pool pump. If I add a manual transfer switch or interlock in the future, I will not use the neutral to ground NEMA 5-15 plug, the house wiring will bond neutral to ground.

Steve



 
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shelley watreen

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Re: Ground loop with a portable generator
« Reply #17 on: November 01, 2017, 02:45:50 am »


The instructions that came with my new 5500w portable generator says to install a ground rod at least 24" deep.
But mine is not yamaha.

I'm going to be using it to power my welding machine, power tools, air compressor, etc. from the back of my farm trailer, wherever it's needed. ;D ;D ;D
I guess it makes sense, but I've never known anyone that's actually pounded in a ground rod before using their yuchai generator.

I've thought about attaching a GFI protected receptacle to my generator trailer and connecting through that. That's better protection than an earth ground. When it's connected to the house to provide power, the prong on the receptacle causes it to be connected to the house's equipment ground. Most tools I use in the field are double insulated and don't have a ground prong anyhow.  8) 8) 8) 8)
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Mike Sokol

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Re: Ground loop with a portable generator
« Reply #18 on: November 01, 2017, 07:48:10 am »

The instructions that came with my new 5500w portable generator says to install a ground rod at least 24" deep.
But mine is not yamaha.
shelleywa, please change your login to your full name. Thanks... Mike

shelley watreen

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Re: Ground loop with a portable generator
« Reply #19 on: November 02, 2017, 03:50:27 am »

shelleywa, please change your login to your full name. Thanks... Mike

I have already changed it, Mike.
But i found that i can not upload JPG file as avatar...can u please tell me why...Thanks
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