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Generators & Electric Motors General Discussion

Generator neutral ground bonding?


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  #1  
Old 11-15-2018, 03:46:27 AM
Railroads Railroads is offline
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In light of my post being misinterpreted. I have decided to try and write a shorter post of what I have here.

I have two portable generators.

My old Coleman Powermate which is 4KW and has the Nema 6-15 240 outlets. Three wire neutral-ground bonded together.

My new generator is a Homelite LR5000T (Thanks Steve Dawkins.) It has the L14-20 outlet but also is neutral-ground bonded despite being 4 wire.

I have a older model Reliance transfer switch 20 amp and a outside plug in for my generator. In order to connect the Coleman 4KW I went out and got a Nema 6-15 240 plug and made a short pigtail cable to go to my L6-20 SOOW cable which is 12/3 20 amp 250 volt.

The reason for doing the above was to avoid chopping the plastic endbell of my Coleman Generator and installing the L6-20 plug directly in the generator head. First off the output is only 15 amps per leg and second the end bell is extinct as a replacement part.

The Coleman 4KW would be plugged into the Reliance switch via the 29 feet of SOOW 12/3 cable.

For years here in the states 240 was just three wire. Now it's 4 wire as people get more safety cautious

With the arrival of my new toy the Homelite 4600 watt generator I now have a simply problem.

My SOOW 12/3 cable is now again incompatible with my new generator.

My original question boiled down to do I really have to change to SOOW 12/4 or could I just swap out the L14-20 plug for the L6-20 connector on the Homelite?

Basically is all this concern over neutral-ground really warranted considering we used a 3 wire system for 240 volt loads for years.

I always earth my generators to my meter base ground rod with 8 AWG jumper cables I cut up to make a portable ground system.

Robert

see later post
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Old 11-18-2018, 10:36:10 AM
cornbinder89 cornbinder89 is offline
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Default Re: Generator neutral ground bonding?

Quote:
Originally Posted by Railroads View Post
The new Homelite (Thanks to Steve Dawkins) is the L14-20 receptacle. Since I plan to now use this generator as my primary and the coleman as the backup should I just swap the L14-20 for my L6-20 or should I get a new length of SOOW 12/4 and rewire my transfer switch back to the 4 prong plug?

Robert
The way I read it he is feeding thru a transfer switch, (what more do you want) and just has a question about neutral bond as different generators have it bonded differently, old ones bonded at the generator, newer one 4 wire not bonded.
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Old 11-18-2018, 01:13:11 PM
Railroads Railroads is offline
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Default Re: Generator neutral ground bonding?

Correct. The gen is connected through a 6 circuit Reliance transfer switch. No interlocking kit available for my 40 year breaker box.

My only question is about the cable and plugs because the Homelite has a 4 prong outlet but neutral and ground are bonded internally. I have the wiring diagram right here in front of me.

Robert

Last edited by Railroads; 11-18-2018 at 08:29:12 PM.
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Old 11-18-2018, 01:54:35 PM
Vanman Vanman is offline
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Default Re: Generator neutral ground bonding?

I would agree. Since the bond in the structure remains when on generator power, there should not be a bond at the generator, and a four conductor cable with four pole plugs and sockets should be used for the connection.
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Old 11-18-2018, 02:02:47 PM
Railroads Railroads is offline
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Default Re: Generator neutral ground bonding?

Keith, Thank you for the reply.

Robert
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Old 11-18-2018, 03:19:52 PM
Frank DeWitt Frank DeWitt is online now
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I am jumping in here just for fun. I take a Kohler automatic start and stop light plant to about 7 shows a year. Fortunately I have very little choice on what to ground to what.

One side of the AC out and one side of the 24 volt battery connection and one side of the magneto are hard wired together. When the generator is off, there is 24 volts DC on the AC line out. The whole thing is mounted on a steel trailer. Approximately 50 light fixtures made before 1950 are connected to the plant through two three way and one four way switches. There are also approximately 30 two pole outlets. The display is split into about 14 circuits, each one with a Edison base fuse.

Now, if anyone is still reading, power leaves the generator and goes to a fuse and a switch, from there it goes to the only modern component, a GFCI outlet. From there, it goes to a key operated switch. (True tumbler lock). And then to the above list. When I am not standing next to the display the key switch is off and I have the key.

Odd facts. When the generator is off the LED on the GFCI outlet is lit (from the 24 volts). If the GFCI should trip, the generator senses the loss of load and stops. At that point, the GFCI can not be reset, because there is no power, and the generator can not be restarted because it can't receive a load. Yes, I have. A work around.

I once had a guy spend about 10 minuets looking it over, then he called a friend to join him. He spent another 20 minuets going over it and then told me that he was a self employed consultant who taught electrical safety to Federal government safety inspectors. He said my display was just fine.
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Old 11-18-2018, 04:16:34 PM
cornbinder89 cornbinder89 is offline
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Default Re: Generator neutral ground bonding?

My understanding. is the three wire 240 volt of old, had no neutral, just two hots and safety ground. That is enough as long as no 120 volt loads are placed on it. With no neutral, bonding is moot point.
The problem come in when 120 volt control loads are used, like in a dryer or modern stove, now you need a 4th wire for the neutral.
Where I am, power comes in from the pole, thru the meter and master dis connect, then branches to the house and barn feeds. Each building has its own ground rod, and the neutral-ground bond is made at each structure. I questioned the electrician about this when I needed a new feeder from the pole dis connect to the house and barn, his reply was that it is correct, only one bond per sub panel, only one sub-panel per structure.
In short, each structure has its own grounding rod and neutral-ground bond, the neutral is not grounded anywhere at the meter or main disconnect.
The way I understand it, what you need depends on where the neutral-ground bond is made on your system, if it is before the transfer switch, then you loose that bond when transferring to generator power, and it would be OK to have the neutral-ground bond at the generator head, but if the neutral ground bond is at the panel (like most) then the generator should not have a neutral bond.
I am no electrician so if I got it wrong, please correct me.
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Old 11-18-2018, 06:25:44 PM
Railroads Railroads is offline
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Default Re: Generator neutral ground bonding?

On my system the neutral ground bonding is outside in the box at the meter which is the disconnect.

The trailers electrical box is the sub panel in this case and the neutral and ground are not bonded.

The transfer switch only switches live conductors and not neutral or ground.

The neutral ground bonding is present in either mode through the utility feed conductors to the outside disconnect box.

The setup I have requires the use of a 4 conductor cable and the separation of the neutral-ground bonding. Simple isn't it.

In practice 240 3 wire of days of old still had neutral connection as dryer motors and oven lights have always been 110v.

Robert

Last edited by Railroads; 11-18-2018 at 06:46:43 PM.
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Old 11-18-2018, 06:59:19 PM
armandh armandh is offline
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Default Re: Generator neutral ground bonding?

Assuming that the transfer panel also transfers the neutral
I would convert the Coleman to 4 wire if possible or
if there are no 240 volt loads use two 120 volt plugs to feed a 4 wire socket
this assumes 240 volt between the hot legs of the duplex outlet.
it doubled up neutrals and grounds but they are separate back to the bonding point

the problem is a 240 volt load would bring the 120 back to a possible un-pluged live prong
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Old 11-18-2018, 08:24:08 PM
Railroads Railroads is offline
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Default Re: Generator neutral ground bonding?

Transfer switch does not switch neutral or ground. Only live conductors are switched.

In practice I have no control over the neutral-ground bonding on the supply coming in. The combined meter box/main disconnect is the point of this connection. Anything beyond that box is my problem. Thus the trailers box which is the sub panel in this case.

The old Reliance transfer switch just switches live conductors.

Robert
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