# Generator without twist-lock outlet



## redfred (Feb 6, 2019)

Hi all. I need some advice before investing in a transfer switch/panel and an electrician's visit. I was given an older Craftsman 4750 watt generator that had seen little use and seems to start and run fine. It has two 120V 15 amp outlets and two 240V 20 amp outlets, all simple female receptacles. There is no single twist-lock receptacle that most newer generators seem to have. Can I use one of the 240 outlets to supply the new panel, and if so, is there an adaptor cord to use that is suitable for this situation? If not, can the generator be re-wired to add a twist-lock outlet? Or...…? Thanks for any advice and guidance.


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## tabora (Sep 6, 2018)

I'm assuming it's a Craftsman Model 919.679470 or equivalent...

The manual can be downloaded here: https://www.manualslib.com/download/782424/Craftsman-919-679470.html

Your generator has 20A total capacity at 240V. You can use an adapter like this to go from the 6-20 outlet to a standard L14-30 generator cable (or just wire it directly): https://www.amazon.com/NEMA-6-20P-L14-30R-Plug-Adapter/dp/B00DL91092


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## motormonkey (Jul 10, 2016)

To properly wire a generator into household wiring, you need a ground, a neutral, and the two 240 v lines coming from the generator. The ground and neutral conductors within the generator must NOT be bonded together. (They are bonded together somewhere in your household circuit, and this is the ONLY place that these two lines should be bonded together.)

There are two problems with using that adapter:

The 240v/20a outlets on that generator only have three conductors, a ground conductor, and the two 240 lines. (no proper current carrying neutral)


The neutral and ground are bonded together somewhere inside that generator.


I'm sure that connections are available within that generator to connect an L14-30 type receptacle into its circuitry, but you are going to have to have someone do it correctly (and SAFELY.)


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## redfred (Feb 6, 2019)

Thanks both of you for your responses. That is the correct model and I have the owner's manual but there is no wiring diagram. Should I (or the electrician) be looking for a wire attached to the generator frame which should then be detached and become the neutral wire to the outlet receptacle? Does the ground bolt on the generator frame not have to be connected to earth when the generator is operating through the transfer switch to the house panel?


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## motormonkey (Jul 10, 2016)

Finding where the neutral is bonded to ground will require pulling some wiring covers off and finding the output wires from the generator windings. Without a wiring diagram, you'll likely need an ohmmeter or a continuity tester and some knowledge of generator wiring for this. The center tap of these windings (could be one or two wires) is neutral. It is usually bonded to the metal generator housing or the external metal wiring housing under one of these covers. 

I have an older generator that only had 120 and 240 receptacles similar to what you have, and it wasn't too much trouble to pull some covers and find the lines coming from the generator windings. I wound up fabricating a panel with an L14-30R receptacle on it to replace the original panel and old receptacles.

Properly wired, the generator is grounded through the ground system in your house, but it never hurts to hook the generator directly to a ground rod too.

BTW, if you do open the ground/neutral bond, and you ever decide to use the generator in stand-alone mode, you'll need to restore that ground/neutral bond. A lot of generators have a jumper that can be removed or reinstalled just for this purpose. A lot of older generators don't though.

This is something that should be attempted only by someone who knows what they are doing. If you don't feel confident in doing it yourself, you need to find someone competent to work on generators.


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## tabora (Sep 6, 2018)

The whole floating vs. bonded neutral thing is quite misunderstood generally. Only certain transfer switches require a floating neutral. In general, it's fine to connect a generator with a bonded neutral directly to a safely interlocked distribution panel or a transfer switch, as long as the generator doesn't employ GFCI on the output. Here's a good video on the subject:




Do not use a separate ground rod at the generator, which can cause a ground loop. This occurs when two points of a circuit both intended to be at ground reference potential have a current potential between them. You should only use a ground rod when the generator is run standalone.


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## motormonkey (Jul 10, 2016)

Yes, the whole floating vs. bonded neutral thing is quite misunderstood.

When electrical current flows through an electrical conductor, there will be a voltage drop across the conductor. This is basic Ohm's law.

The current path in a 220 volt circuit is through the two line conductors. The current path in a 120 volt circuit, though, is through one of the line conductors and the neutral conductor. Because of Ohm's law, there will be a voltage drop across the line conductor *and the neutral conductor*.

If the neutral conductor is bonded to the ground conductor at the generator and the generator does not have its own ground, the voltage on the neutral conductor caused by this voltage drop will be present on every metal part of the generator.

In most cases, the voltage will be small, but it still presents a shock hazard. This is why the electrical code dictates that there be a single point of bonding between the neutral and ground.


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## redfred (Feb 6, 2019)

Thanks everyone for the helpful information and advice. At least now I think I can have a conversation with my electrician with some understanding of what needs to be done.


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