Can 120v generator work with backfeed breaker?

BreakerOffJanuary 11, 2012

Hi. It has been a long time since I posted here. I'm happy to see this forum is still thriving!

I have a Honda EU2000i generator which supplies 120v, not 240v. Originally, my plan was to use a few extension cords to power my refrigerator, two 60-watt lights, and my computer. I figured that it wouldn't be that inconvenient to run extension cords through an open window.

Well, we had our first power outage and I ran the lines through the window and into a few rooms on the first floor. Now that I've had a taste of the inconvenience of doing it this way, I wanted to have an electrician install a power inlet box, backfeed breaker and Interlock Kit on my Square D QO panel.

The electrician informed me that it won't work because my generator can't supply 240 volts to the panel. Now I'm regretting the EU2000i purchase because I didn't do enough homework. But I like this small Honda because I'm not looking to power the whole house, it's very quiet and it's an inverter.

Is there any way to make this work, aside from buying a 120v/240v genset?


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While there are others on this forum that may be able to provide alternative solutions, I'd suggest something like the product in the following link. You only install it into specific circuits that you then manually switch over from line power to generator power. There are several 120/240 versions available as well but this is one of the ones specific to 120V.

Here is a link that might be useful: Reliance Controls 4 circuit 120V transfer switch

    Bookmark   January 11, 2012 at 7:35PM
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You can do it, but you have to choose what half of the circuits you will power. The other half will remain dead. You should turn off all the other breakers on the powered leg so you do not overload the generator. In addition to that, you must turn off the 240V, tied breakers or you could run into real trouble.

You can settle for the refrigerator circuit and the outlets and lights that are on that 'leg' of the service panel as one option. If you want to spend a little more money, an electrician might be able to move some lights and convenience circuits to the same leg as your refrigerator circuit.

If you are going to do the latter, you could compare the cost of that solution to the small transfer switch type that yosemitebill suggested. It might not be that much more.

    Bookmark   January 11, 2012 at 8:10PM
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Thanks for the replies. I'll look into the transfer switch.

The electrician did tell me that I could energize one leg but he said that there still may be a problem with the neutral. I can't remember exactly but I think it had to do with overloading the neutral.

    Bookmark   January 12, 2012 at 10:30AM
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Ron Natalie

If you only feed one leg, there's no way to overload the neutral any more than overloading the hot leg.
It's possible you could mess things up if you tried feeding both legs with the single 120V leg from the generator.

As pointed out any 240V loads are really going to mess things up (as well as potentially damaging the load device).

    Bookmark   January 12, 2012 at 10:53AM
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I think Honda sells a kit that allows you to use two generators to power both legs.

    Bookmark   January 12, 2012 at 2:01PM
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Ron Natalie

Honda does have a sync kit that lets you hook two of their little generators together to make 240. It only works with the specific generators it's designed for its not something you can hook to any generator and DO NOT just run two unsynchronized generators into a 240 system. In that case you very well may burn up the neutrals and damage stuff.

    Bookmark   January 13, 2012 at 6:33AM
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Yeah, and by the time you buy two EU2000's you can have one hell of a nice 6500 watt middle of the road genset.

    Bookmark   January 13, 2012 at 3:28PM
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Ron Natalie

The big advantage of the little honda (First gear, it's all right) is that they are QUIET and easy to carry. But you're right for most situations you can get a real nice 240V generator for the price of these little guys.

    Bookmark   January 13, 2012 at 8:19PM
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After looking at the transfer switch, I am going to go that route. I'll probably get the 10 circuit model so I have access to more stuff in the house. Don't worry, I won't overload the generator. :) I have been on enough film & video shoots to know the limitations of generators.

If you'll indulge a few more questions....

I'm planning on putting in a 30 amp 125/250 power inlet box with 10/3 NM cable in case I decide to buy a bigger genset in the future. Considering my current Honda only supplies 120 volts on a regular household receptacle, how can I modify a generator cable to go from 5-15p to L14-30r? Can I buy an L14-30 generator cable and cut off the male end to put on a 5-15? Someone told me that all I'd have to do is put both hot wires onto the brass screw in the 5-15p connector. Can a 5-15p connector accommodate the fat 10-gauge cable?

    Bookmark   January 14, 2012 at 10:54PM
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Ron Natalie

The cheapest way is probably just to buy some 12G cord at the home center and a 5-15P and a L14-30S.

You can get 25' of 12G cord for under $25. The plug will run you a couple of dollars you may not be able to find a L14-30S at the home centers but you can probably find it online.

    Bookmark   January 15, 2012 at 6:32PM
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Rather than chopping up a relatively expensive gen-set cord, either take ron's suggestion and make one up, or purchase a 12G 120V extension cord and replace the socket end with a L14-30 socket.

I've seen the sockets at both Lowes and Home Depot but they're a little on the pricey side. Last time I needed one I found one on Amazon - I'll attach the link.

BTW - Since you are manually switching the individual circuits from line side to generator side, I'm having a hard time thinking of a reason why you could not parallel the two legs on the socket end and monitor load - as long as you don't switch in any combination 120/240 loads - which "may" have the potential to cause appliance damage. So, it may be best to only wire one side of the socket, and stay on just one leg of the transfer switch.

Here is a link that might be useful: One of Amazon's links for the socket.

    Bookmark   January 15, 2012 at 7:36PM
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Ron, since I may buy a 120/240-volt generator in the future, I'd like to buy the cord once and be done with it. You're right, I could get away with 12-gauge for now but I'm trying to think ahead a little.

Bill, can you provide more detail on how to "parallel the two legs on the socket end?" I thought it would be better to use 10/3 cable and connect both hot wires to the brass screw on the male end of the cable. Can I easily fit two 10-gauge hots in a 5-15 or 5-20 connector?

Thanks again to everyone for all of their help!

    Bookmark   January 17, 2012 at 4:19PM
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Most 30 amp transfer switch kits come with an expensive (if purchased separately) 10 gauge 120/240 volt L14-30 molded connector twist-lock extension cord to go between the generator and power inlet box. Why chop this up and degrade it?

Your current 120VAC generator can only supply enough power to utilize a 12 gauge/120 volt three wire cable. Just buy a 12 gauge 120 volt cord and change the socket end.

With all due respect, since you are asking about wiring both legs together on the L14-30 socket end now, it makes me even more uncomfortable about suggesting it could maybe be done under the right circumstances.

If you are going to go with a 10 circuit transfer switch, just buy the larger generator now, wire it all properly, and be done with it. However, you still need to evaluate and very carefully calculate running and start-up loads on all these circuits.

    Bookmark   January 17, 2012 at 10:46PM
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Thanks for your thoughts. I don't want or need a noisy, gas-guzzling 240-volt generator right now so I'm going to heed your advice and keep it simple at 120 volts.

I'd still like to future-proof the wiring from the power inlet box to the transfer switch, however, by installing 10/3 NM cable instead of 10/2 or 12/2. That way I can upsize my generator at some point without having to run a new line.

So the question is, in a 120-volt setup is it OK to run 10/3 from a Gen Tran 53002 inlet box and leave one of the hot wires disconnected and capped off with a wire nut? Does it matter which hot wire I leave disconnected? (The reason I want to use the 30-amp inlet box instead of 20-amp is in case I upsize to a Honda 3000-watt 120-volt generator.)

And yes, I have very carefully looked at the 10 circuits I plan on hooking up. I won't be using them all at the same time. I just want the convenience of having them available. At most, all I will run at one time will be two 60-watt lamps, TV, FiOS set-top box, FiOS ONT box and refrigerator. That's what I ran on extension cords during the last outage and the EU2000i generator sipped gas for over 8 hours until the power came back on. It could have gone longer before refueling.

Thanks again. This has all been extremely helpful and I feel better about how to proceed.

Here is a link that might be useful: Gen Tran 53002

    Bookmark   January 18, 2012 at 12:56PM
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OK, I now understand you are talking about the feed from the generator inlet box to the transfer switch. Yes, that should be a 10/3 connection.

Have you looked at the Reliance Controls 10 circuit transfer switch as well as installation instructions for both brands?
Two slightly different approaches to the way they connect and install - could be useful to look at and compare.

Here is a link that might be useful: Reliance Controls 10 circuit transfer switch at HD

    Bookmark   January 18, 2012 at 7:27PM
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I am planning on getting the Reliance 10-circuit. Unless I'm mistaken, the only difference between Reliance and Gen Tran is that Gen Tran uses red and blue wires instead of red and black. Otherwise they look the same.

Incidentally, I asked Reliance why their boxes look identical to Gen Tran and they said that Reliance used to manufacture for Gen Tran, but no longer. Gen Tran simply kept the design. Doesn't quite make sense to me but that's what I was told.

    Bookmark   January 18, 2012 at 8:43PM
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Hmm... That's interesting. I found the transfer switches you were talking about - they call it their "Vintage" line.

The transfer switches Gen Tran commonly sell now are installed like a sub-panel and require a new 60 amp breaker in your main panel. You then reroute all your switched circuits to breakers in the Gen Tran panel and no longer use the original breakers. The master transfer switch in the Gen Tran panel then switches between line/generator.

The Reliance Controls simply interrupt and switch the individual circuits from the main panel at the transfer switch between line/generator. Each circuit has a built-in breaker on the generator side and use your existing breaker on the line side.

    Bookmark   January 18, 2012 at 9:33PM
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Oh, whoops. I thought you were comparing apples to apples. Yes, I have browsed both sites and looked at the good/better/best products. I'm trying to keep this somewhat simple with a self-install, so the Vintage switch seemed the most economical and doable. Not to mention my tricky 120-volt generator issue. Fair to say the subpanel solutions probably wouldn't play nicely with only 120 volts.

    Bookmark   January 18, 2012 at 11:27PM
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UPDATE ONE YEAR LATER: I finally got around to installing the Reliance Q310C transfer switch. I took Bill's advice and bought a 12-gauge extension cord, cut off the female end and replaced it with the L14-30. For the hot wire inside the power inlet box, I connected only the 10/3 black wire and capped the unused red wire. Then at the transfer switch (following the advice of Reliance tech support), I pigtailed the incoming black wire and connected two tails to the black and red terminals, thereby supplying 120v to each leg in the service panel. (Of course, the 10/3 neutral and ground were connected as well.)

Tested it and it works perfectly. I can't run much at one time because of my small generator but that's OK. I've also bought several led light bulbs that only draw 13 watts each, so that means I can use around 5 lamps instead of only ONE incandescent 60-watt lamp.

Thanks again to all who worked through this with me!

    Bookmark   February 21, 2013 at 9:59AM
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Thanks for the follow-up, Breaker. I'm looking into powering both legs of my 240 panel with a single 120 generator, sort of along the line of what you were looking to do. I've already bought an interlock kit for my DO panel and really want to avoid using a transfer box. My plan was to wire it with 8/3 (for if I ever upgrade to a bigger generator) all the way out to the outside connection box. And I already have a 10/3 outside cable where I was planning to cut the generator side of the plug and replace it with a 10/2 plug, connecting both hot wires of the 10/3 wire into the single hot connector of the 10/2 plug.
I thought I had it all figured out when I bought all this last year, but now having a little concern about powering both legs at the box with the single leg from the gen. I do know about being careful to stay under load limits and keeping off any 240 loads. This setup seems to be the simplest and at the same time offers the most flexibility about which circuits I want to power, and stay with a small 4k watt generator to keep noise and fuel consumption down (important for neighbor and fuel availability reasons). I welcome and would appreciate advice from anyone on what I mentioned above. IâÂÂm a computer tech but a have a lot to learn when it comes to house wiring.

This post was edited by rmui on Wed, Mar 6, 13 at 15:49

    Bookmark   March 6, 2013 at 3:10PM
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Sorry, I need to make a small correction to what I posted on February 21, 2013. I did not put a female L14-30R connector on my extension cord, I put a female L5-30R so that it would connect to my GenTran 53002 power inlet box.

Wanted to straighten that out for anyone who comes along in the future!

Here is a link that might be useful: Leviton L5-30R connector

    Bookmark   March 6, 2013 at 5:34PM
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And as you likely found out, purchasing a cord and then removing one end is often less expensive than purchasing the same cordage off the roll and two cord ends.

I have a number of very old power tools that had hardened rubber cords that had cracked (one of the tools is a Boice-Crane scroll saw with a 27 inch throat that had a cord at least 80 years old.

Purchase a cord, cut off the female end, and wire it up.

    Bookmark   March 7, 2013 at 12:02PM
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I found these pretty good directions on making your own cable:

Also, keep in mind that they don't sell these cables for a reason. The main one I found is that if you have any multi-branch wired circuits, it could overload and cause a fire.,26267406

    Bookmark   June 19, 2013 at 8:19PM
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