I have an old 5KW generator with an L6-20 and a 5-20R duplex receptacle. From the generator itself there are two black and two white wires going to the distribution panel. Nominal voltage is 120 between black and white, and 240 between black and black. Inside the panel, the two black wires go first to the X and Y lugs on the L6-20 (the ground lug is not connected--that seems odd), and then each black to one of the two hot terminals of the 5-20R. The white wires go to the neutral terminals, and then to the ground terminal. So far so good.

I want to replace the L6-20 with an L14-20, which is now standard for use with things like transfer switches. So my question is, should I

1. simply run the two hot wires to the X and Y lugs on the L14-20, the neutral wires to W, and leave the ground lug unconnected (essentially, what I have now),

2. connect the neutrals to both W and ground, or

3. run a separate ground from the distribution panel to the ground lug on the underside of the generator frame?

Thanks!

Hmm... wouldn't it be simpler to just change the plug on your cord?

You want the real best answer, right?

You should provide a removeable strap from ground and neutral.

If used as stand-alone, the strap should be in place.

If used as a house backup, the strap should be removed.

Why:
When installed, it allows protective ground to work.

When not installed:
When it's not installed you have an isolated power source. So, isolated is better if you have a one choice.

If installed, the system will use the reference of the house where ground and neutral connect. There should only be one of these connections. So, ground isn't connected at the panel.

Then there are transfer switches that switch the neutral and you'd do something different like put a ground rod at the generator and use it for the grounding electrode.

Help? Or clear as mud?

Unfortunately, no. The L6-20 delivers only 240V between X and Y. There's no provision for delivering 120V between X or Y and neutral. There is no neutral in an L6-20. Running neutral through the ground wire doesn't sound like a great idea. That's why the entire world has switched to the L14-20, which adds the neutral wire.

If you mean a removable strap between ground and neutral at the generator distribution panel, I think that won't help for the following reasons. First, neutral and ground are already bonded at the 5-20R receptacle. Even if that connection were removed, ground and neutral are bonded 8" away inside the generator housing. So it's not like a subpanel in a shed where you unbond and sink a separate ground rod. There's no danger here of a ground loop. Plus, all modern generators connected to a house transfer switch via an L14-20 work without any removable (and hence forgettable and therefor dangerous) additional straps, all without fracturing the code. Finally, the L6-20 and the 5-20R can be used simultaneously, so there really aren't separate stand-alone and house backup modes that could be enforced.

So my question still comes down to what to do with the ground lug on the L14-20. Ignore it, bond it, or ground it?

First, I'm not an electrician but I just went through this with my electrician. It took a while but now I understand it.

KISS is right. He is giving you his best answer and it does meet the NEC requirements exactly.

In the generator you need to unbond the neutral and ground unless your transfer switch switches neutral. Most don't. According to code, there is ONLY to be ONE location where neutral and ground are tied together and that is the main service panel. Most people running a portable generator on a transfer switch don't know or don't care that they need to make sure that there neutral and grounds aren't tied together at the generator.

When running a load plugged directly into the generator you then need to bond neutral and ground. This is the default wiring for most portable generators.

I would suggest that you isolate the neutral and grounds in the generator. On the L14-20, tie the ground to the chassis of the generator. The neutral on the L14 goes to the neutral of your generator.

Make up a plug to go into another outlet that ties the neutral/ground together for use ONLY when you run a load independent of the transfer switch -- it'll be the "removable strap" that KISS calls for.

It gets complicated if you are feeding a transfer switch and running a load off the generator at the same time. In that case you're all set as long as you're connected to the transfer switch. As soon as you disconnect from that switch though you'd need to bond neutral/ground again.

Last sentence of the last paragraph.

Your generator leaves the ground off because it's an isolated power source which is technically OK. But it might not be if you were using a grouned tool on a wet pavement. Yea, I can always find some stupid exception for some idiot because they always make better idiots.

The rule that can't be violated is:

There can only be ONE AND ONLY PLACE where neutral and ground get bonded together.

We want to achieve that when operating stand-alone and when operated as part of a transfer switch or backfeeding.

It's less important when operating the generator stand-alone.

The last think you want is a difference in ground potentials.

The plug is an OK way to make the strap, but I'd change one of the duplex receptacles to hospital grade.

You could actually use an isolated ground receptacle and have a separate bonding jumper, so you can use the 120 outlets at the same time as connected to the transfew switch.

I can't think of a good way of making the strap.

The GFDB2 here might be a good way. Sherco Auto Supply

Just create a bar and move from side to side. One side is conncetd and the other side is not. Quice/easy. If you put a kill switch on the case, you have it made. You have to make the change with the engine stipped. It would easily show which way is correct.

Just some ideas.

Sorry for the delay in posting a response. It seemed to me that any solution that required the generator to be disassembled and rewired (not such a good idea), or the fabrication of a "strap" that anyone who used the generator would have to know how to use and also remember to do so (a potentially lethal idea), had to be off in the weeds. So I did some research, and found the following article to be very helpful:

http://www.schneider-electric.ca/www...pl_Note_EN.pdf

It has diagrams of all the permutations, and a clear description of why the bad ones are bad. More importantly, it provided a couple crucial missing (for me) details. First, generators are manufactured one of two ways: “Neutral Bonded to the Frame” and “Neutral Floating”. This information is supposed to be stamped on the nameplate. Mine is so old it doesn't have it. I called the manufacturer, who told me it was the former; I confirmed it with a meter. Second, transfer switches relevant to this situation are either 2-pole or 3-pole.

If the generator is “Neutral Floating”, use a 2-pole switch. If it's “Neutral Bonded to the Frame”, use a 3-pole switch. It's that simple.

So, the answer to my original question is option #2. The current wiring now makes perfect sense. Ground and neutral are connected at the 120V 5-20R receptacles, and should be connected at the L14-20 as well. This is the correct configuration for both standalone and transfer switch use.

Thanks to all who took the time to answer.

The application note is surperb.

With portable generators and simple transfer panels, it's difficult to put in a transfer switch.

Take for instance:
1) The backfed breaker with an interlock kit.
2) The GENTRAN small transfer panel

I believe, in both cases, the neutral isn't switched.and it would be difficult doing so.