Grounding portable generator with manual transfer switch (No, not again!!!)

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Tim K

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I know, I know. There are countless threads about grounding portable generators, but most of them are pretty specific to each scenario. I've read them all. I know there are plenty of opinions on the subject and I hope I can just get a few of them! This ties in with a post I made a few months ago, but that's locked now so I have to start a new thread I guess....

The house was built in the early 90's. There is a single grounding rod buried by the service entrance for the gas and electric. The main panel has a ground wire run to the rod outside, as well as a second ground wire clamped to a nearby water line (about 30ft after the meter). There is a jumper over the meter. Without digging up the front yard I can't be certain, but I'm pretty sure the water service is metal from the street.

The generator is setup to run on the back of the house because it is partially sheltered by a deck, and is also away from the neighbors to keep the peace. A power inlet box will be mounted on the wall and wired to the manual transfer switch located next to the panel. The transfer switch (Generac 6294) does NOT switch neutral. The generator is a 7000W/8500W portable generator. The generator came with the neutral bonded but the bond was removed as per the manufacturer's instructions.

By definition this would be a Non-SDS, and thus wouldn't require it's own grounding system, only that it be tied to the building's GES.... Correct?
A 30amp circuit calls for a 10ga ground wire (coated green), which would be run unbroken to a nearby copper cold water line.

All of this is shown in the attached graphic.

Are there any flaws in this setup? First, as far as grounding the generator to the building's GES.....is tying in to any part of the water line sufficient? I couldn't find anything in any codes that specified where the connection to the GES had to be made.

Obviously today's code requirements for grounding the main service would be different. I believe it would require at least one more grounding rod buried at least 6ft from the first, and also the ground wire from the main panel to the water service would have to be attached within 5ft of the service entrance. I don't think doing either is 'required' since this is all grandfathered in so-to-speak. But if it were your house, would you bother to drive another rod? Would you run a new ground wire from the panel the extra 30ft to the water service entrance?

Thanks for your input/insight.

genset.jpg

-Tim
 
Looks Good

Looks Good

As long as the transfer switch prevents back-feeding of
into the service and the grounding in your layout above
is solid it seems to be fine.

Disclaimer: I am looking at this from a utility perspective,
and not from a NEC code view. The transfer switch is to
protect the line/cable crews from a back-feed.

So I think your plan is well laid out, but do see if the NEC
does require the extra ground rod you mentioned.

I hope your install goes well and I think your plan will
work out fine. Just check (I think section 702 of the NEC
will give guidance on the issues of your concerns)

JR
 
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JRW 70 said:
As long as the transfer switch prevents back-feeding of
into the service and the grounding in your layout above
is solid it seems to be fine.

Disclaimer: I am looking at this from a utility perspective,
and not from a NEC code view. The transfer switch is to
protect the line/cable crews from a back-feed.

So I think your plan is well laid out, but do see if the NEC
does require the extra ground rod you mentioned.

I hope your install goes well and I think your plan will
work out fine. Just check (I think section 702 of the NEC
will give guidance on the issues of your concerns)

JR
Click to expand...

Yes, the Generac transfer switch isolates the select 6-10 circuits from utility power. There is a lockout that prevents you from drawing power from the generator feed without shutting off the breakers fed from the main panel.

product_9440_600.jpg

Thanks for your thoughts. Hopefully I'll get some more feedback.
 
You have over thought this situation. Read 250.34 (1) & (2). As long as you are connecting to the receptacle on the generator with a cord and plug set up, and as you have stated, you will be using a 3 wire with ground cord you are good to go. No need to run any other wires to ground rods or water lines.
 
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ceb58 said:
... As long as you are connecting to the receptacle on the generator with a cord and plug set up, and as you have stated, you will be using a 3 wire with ground cord you are good to go. No need to run any other wires to ground rods or water lines.
Click to expand...
I concur, coupled with OP stated N-G bond removed on generator. The ground wire in the cord bonds the generator to building GES. Removal of N-G bond eliminates parallel N path.
 
ceb58 said:
You have over thought this situation. Read 250.34 (1) & (2). As long as you are connecting to the receptacle on the generator with a cord and plug set up, and as you have stated, you will be using a 3 wire with ground cord you are good to go. No need to run any other wires to ground rods or water lines.
Click to expand...

Really? I thought that only applied to the receptacles on the unit itself. I'm under the impression that "cord and plug" refers to the directly attached equipment/appliances. (ie. if I plugged a refrigerator into the generator's receptacle). I thought that when you use the twist lock and connect directly to the building's wiring (as I am through the power inlet and manual transfer switch) then the grounded receptacles reference no longer apply.

If that is not the case then adding the additional ground wire for the generator would be unnecessary, but I suppose can't hurt.
 
Tim K said:
Really? I thought that only applied to the receptacles on the unit itself. I'm under the impression that "cord and plug" refers to the directly attached equipment/appliances. (ie. if I plugged a refrigerator into the generator's receptacle). I thought that when you use the twist lock and connect directly to the building's wiring (as I am through the power inlet and manual transfer switch) then the grounded receptacles reference no longer apply.

If that is not the case then adding the additional ground wire for the generator would be unnecessary, but I suppose can't hurt.[/QUOte

If you connect the switch to the generator with a 4 wire cord and plug set you have met the code. No need to run any other wire any where else. Just something to trip over.
Click to expand...
 
Tim K said:
Really? I thought that only applied to the receptacles on the unit itself. I'm under the impression that "cord and plug" refers to the directly attached equipment/appliances. (ie. if I plugged a refrigerator into the generator's receptacle). I thought that when you use the twist lock and connect directly to the building's wiring (as I am through the power inlet and manual transfer switch) then the grounded receptacles reference no longer apply.
Click to expand...
A NEMA 125/250V twist-lock is a grounded receptacle.

Tim K said:
If that is not the case then adding the additional ground wire for the generator would be unnecessary, but I suppose can't hurt.
Click to expand...
The ground wire (EGC) is required, as with all feeders.
 
That all makes sense. I never thought about it that way. I knew there was a ground wire in the twist lock cable and in the wiring to the transfer switch. I just read that the code required a tie-in to the building's ground system and automatically assumed it meant a separate ground wire. I guess I did in fact over think this!

Thanks!

-Tim
 
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