20 amp generator but 30 amp inlet box

alphapepperApril 27, 2009

Hello,

My house has a 30 amp generator transfer switch with a 30 amp inlet box mounted on the exterior. My generator only has a 20 amp connector. Is it possible to power a 30 amp switch with this generator, just reduce the number of circuits enabled? I don't want to buy another generator if I don't have to. I'd rather splice a 20 amp to 30 amp cable. Thanks for the feedback.

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pharkus

Yes.

The generator should have a circuit breaker built into it, which will trip if you pull too much power.

More than likely, it will work fine. You will learn quickly from experience what loads you cannot attempt to run together from the generator.

    Bookmark   April 27, 2009 at 9:43AM
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davidandkasie

you just need to get the 30A plug to fit the end of your existing genny cord. if you don't have a cord, get one with a 30A plug on one end and a 20A on the other.

    Bookmark   April 28, 2009 at 11:23AM
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chanesworth

Sorry to bring this up again but I have the same issue. A guy at one of the big box stores told me that I could get a 30A cord and that it wouldn't matter that my generator has a 20A plug. He stated that the 30Amps was capable of carrying more electricity. I would only get into a problem if say I was trying to use a 20A cord with a 30Amp generator. Second, I did not realize that you could get a cord that has a 20A male and 30A female ends. Would this be a problem? Sorry, I am a neophyte when it comes to electrical stuff. Just don't want to waste money buying the wrong cord. Thanks

    Bookmark   June 16, 2010 at 5:17PM
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petey_racer

I doubt you can buy this cord, but you CAN make it.

    Bookmark   June 16, 2010 at 8:07PM
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stinkytiger

Hi,

The person in the store is correct. In general it does not hurt to have ticker more chunky wires. You have more capacity. The downside is the cost.

If your genset can only deliver 20 amps, then I would:

1) Buy a 20 amp power cord. You can go for a 30 amp cord as well. But since your genset will not put out more current than 20 amps anyway, you can save some money by going with 20 amp rated power cord.

2) Buy a 30 amp socket and attach this to the end of your power cord. The plug type on the wall of your house if probablly a NEMA type. See the link. Buy a SOCKET (Home Depot) that will fit your plug. As a wild guess it is a NEMA L14-30R, note I have never seen your house!

3) Buy a 20 amp plug which will fit into your generator. Again a wild guess, NEMA L14-20P. (Home Depot)

You have four wires to hook up. A ground, a Neutral, and two lives.

One final thing you have to think about a bit is to check your generator ground neutral bonding. This is where it gets a bit complicated and it depends on your transfer switch.

http://members.rennlist.org/warren/gt5000c.html

See this web site for more info.

Best, Mike.

Here is a link that might be useful: NEMA Plugs and sockets

    Bookmark   June 17, 2010 at 7:24AM
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chanesworth

Thank you very much for your responses. You have made this issue much clearer for me.

    Bookmark   June 17, 2010 at 8:25AM
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chanesworth

@stinkytiger: I do have a 20Amp power cord (that I used at my last home.) On one end it has L14-20P plug that goes into the generator. I was planning on getting L14-30 socket that would go into the inlet box attached to my house (I checked and this is the correct part). My 20A cord is a 12 gauge / 3 wire (black/white/green). I was told today when I went to the store to buy the socket that I could not use my existing 20A cord because it is 3 wire and I need a 4 wire to work with the 30A socket. Is this correct? I promise that this is my last question (I think) :)

    Bookmark   June 17, 2010 at 2:29PM
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stinkytiger

Hi Mr. Chanesworth,

Hmmm ... we have to be a little bit careful here. What used to work at your old house, may not compatible right away at your new house. Although if we had all the details it can be made to work. However geting a detail wrong is not going to be good.

At this point I would recommend getting an electician to check things over since this is getting site-specific.

If I were to guess this is what I think happend at your *OLD* house. The Grounds of the Plugs Socket are connected with the green wire. One of the Lives is connected with the Black wire, the Neutral is connected with the white wire. The other live from your generator was not connected. (This assumes your generator has two phases which most do). So in effect at your old house you were using 1/2 of the generator only.

Typically you would have a 4 wire cord, hence you could go L14-20P (genset plug) to L14-30R (house receptical). Green=earth. White=Neutral, Black=Live-1st, Red=Live-2nd. Note each live is one "PHASE" of your generator set.

What confuses me, and hence my recomendation for an electrician is that you have a three cord to a 4 way plug. Why was this done at your old house? Was it something special with your generator, your house or some other reason? What about your new house, what is special there?

So where to start. What genset do you have? Do you have a manual? I would start there. If you are unsure, as I am right now, use an electrican since getting it wrong is bad.

Sorry I am not much help here, I just do not want to put your or your familly in any danger.

Warmest regards, Mike.

    Bookmark   June 18, 2010 at 10:48AM
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chanesworth

Thanks Mike. I had a "friend" make the cord for me at my old house. I am not sure why he used a 3 wire cord, but this time I am going to get a 30A cord (4 wire) and add the L14-20P on one end and have the L14-30R on the other end. Thank you again.

    Bookmark   June 18, 2010 at 4:56PM
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