Four-prong Generator Inlet, But Three-prong Outlet On Generator... What Should I Do? - Electrical - DIY Chatroom Home Improvement Forum
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Old 06-30-2016, 09:00 AM   #1
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Four-prong generator inlet, but three-prong outlet on generator... What should I do?


I've installed a generator inlet for a newly-acquired generator. I used existing wiring from a hot tub hook-up that was installed by the prior owners, but is no longer used. As I explained in this thread:

http://www.diychatroom.com/f18/use-e...ook-up-410282/

the existing wiring included a 50-amp, dual pole breaker in the main breaker box, and then another 50-amp, dual pole, GFI breaker in a separate box in the garage., just below the main breaker box. From there, four wires are ran to the backyard. I'm not sure what gauge it is, but it is THICK... might be 4 gauge wire, or 6 at a minimum.

The wire goes into a fuse box, and then went out of the fuse box to the hot tube. I removed the fuse box and the wire that previosly went from the fuse box to the hot tub. In place of the fuse box, I installed this four-prong generator inlet (nema L14-30P):



I ran the black wire to the x, the red wire to the y, the ground to the ground, and the white to the w.

Unfortunately, I just realized that the generator has a three-prong plug (nema l5-30r). How do I hook up the 3-prong generator to the four-prong inlet? I could get an adaptor, but what happens with the extra wire? Can I just use one hot instead of two? Can I split the one hot from the generator into two?



TL;DR: How do I hook up a generator with a three-prong outlet (nema l5-30r) to an inlet that has four-prongs (nema L14-30P)? What happens with the extra wire going from the inlet to the breaker panel?
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Old 06-30-2016, 09:15 AM   #2
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


The L5-30r is a 125 volt receptacle. The L14-30p is a 125/250 volt receptacle.

If your generator does not have a 120/240 volt 4 wire output then you can make an adapter using a L14-30r to plug into your house inlet. Run a jumper wire from the x and y terminals. White goes to w, ground to ground. Both legs of your main panel will be tied together this way.

If you have any MWBC's in your house you could overload them doing this.
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Old 06-30-2016, 09:33 AM   #3
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


Quote:
Originally Posted by AandPDan View Post
The L5-30r is a 125 volt receptacle. The L14-30p is a 125/250 volt receptacle.

If your generator does not have a 120/240 volt 4 wire output then you can make an adapter using a L14-30r to plug into your house inlet. Run a jumper wire from the x and y terminals. White goes to w, ground to ground. Both legs of your main panel will be tied together this way.

If you have any MWBC's in your house you could overload them doing this.
Thanks... I'm not aware of an MWBC's in my house... is there any way to check? My house is relatively new... not sure if that makes a difference.

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Originally Posted by AandPDan View Post
Both legs of your main panel will be tied together this way.
You mean they already are right? I don't have to do anything at the panel, right?

Edit: What gauge wire would be the minimum for the adapter?

The wiring for the adapter would be like this then:

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Old 06-30-2016, 09:39 AM   #4
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


Yes on the adapter wiring. I have the same setup. 10 gauge for 30 amps.

No changes to the panel.

MWBC's should be on a handle tied breaker. Two circuits will share a neutral - usually it's done in the kitchen area. Probably not very common nowadays due to GFCI's.
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Old 06-30-2016, 10:05 AM   #5
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


Thanks... Looks like this is what I need:

https://www.amazon.com/gp/product/B0...=ATVPDKIKX0DER

The two hots are bridged, so that should work. There are some reviews saying the hots are not bridged, but I think they are just confused because it's obviously only going to output 120V if that's what is being inputted. It's a little pricey, but the two plugs at H.D. are almost $70 and that doesn't include the wiring.
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Old 06-30-2016, 10:56 AM   #6
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


Good find.

Yes, you can make your own but with the price of the plugs that makes sense.
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Old 06-30-2016, 11:17 AM   #7
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


Thanks again for your help.
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Old 06-30-2016, 04:21 PM   #8
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


Where is the transfer switch?
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Old 06-30-2016, 05:19 PM   #9
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


I have trouble answering your question without getting a bit passionate.

Simply put: Stop. Don't Touch. Find a real electrician.

Whatever you do, do NOT, in any manner, connect your house wiring to what is clearly a small, portable generator. NEVER connect any sort of generator directly to your house wiring - connect through a properly installed "transfer switch". Period. No exceptions.

Now ... I use a similar generator at my house, in emergencies. It makes just enough power to keep the furnace running and a few lights on. Here's what I did:

I don't want the bugs and weather entering my house either. So, I mounted a similar inlet to my house, The inlet directly connects to a receptacle inside, one that has NO connection to the house wiring.

When I need the generator, I simply run extension cords to the furnace, and a few lights. After the power is restored, the cords get rolled up and put away.
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Old 06-30-2016, 05:48 PM   #10
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


In his other thread he says he has an interlock.

You do OP, right?
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Old 06-30-2016, 05:55 PM   #11
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


Quote:
Originally Posted by Ler0y Jenkins View Post

How do I hook up a generator with a three-prong outlet (nema l5-30r) to an inlet that has four-prongs (nema L14-30P)? What happens with the extra wire going from the inlet to the breaker panel?
Your generator is suited for 240v loads,
It is NOT suited for 120v loads.
If it was meant for 120v loads it would have a forth pin
The" neutral ".
What this means is only bigger 240v loads will work,
smaller 120v loads will NOT work.

What make and model is your generator ?
it MAY be possible to reconfigure the internal jumpers
To get a Neutral ?
Or maybe use a 240 to 120v transformer ?
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Old 06-30-2016, 06:31 PM   #12
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


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Originally Posted by dmxtothemax View Post
Your generator is suited for 240v loads,
It is NOT suited for 120v loads.
If it was meant for 120v loads it would have a forth pin
The" neutral ".
What this means is only bigger 240v loads will work,
smaller 120v loads will NOT work.

What make and model is your generator ?
it MAY be possible to reconfigure the internal jumpers
To get a Neutral ?
Or maybe use a 240 to 120v transformer ?
His generator is 120 volts, not 240.
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Old 06-30-2016, 06:32 PM   #13
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Re: Four-prong generator inlet, but three-prong outlet on generator... What should I


Quote:
Originally Posted by AandPDan View Post
Y

MWBC's should be on a handle tied breaker. Two circuits will share a neutral - usually it's done in the kitchen area. Probably not very common nowadays due to GFCI's.
The handle tie rule is relatively new in the scope of things. I see individual breaker MWBCs all the time in 50's-90's homes.

Also, the GFI thing is not much of an issue. Maybe in Canada where kitchen circuits were commonly split-wired, but installing two GFIs at the beginning of a MWBC and continuing with 2-wire is still very common.
If anything, the draconian new AFCI requirements will kill MWBCs.
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