# 120 Feed T0 240 Panel



## Shadetree Mechanic (Jul 13, 2017)

Just got a brainstorm...would it be appropriate to tie my Honda 3000 (120 volt/30 amp) to my existing 120/240 distribution panel? I would use the single hot generator output to feed both legs of the panel input breaker. The only 240 load in the 40 circuit panel is a central air conditioner condensing unit. That unit would then receive 120 volts on both input legs, but zero volts between them. I chose the Honda for noise reasons and cannot afford one of their larger 120/240 inverter units. Please comment if you can; and thank you!.


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## Handyhiker (Sep 29, 2016)

Not a ptoblem. Just shut off the breaker for the central air.


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## exmar (Jun 29, 2015)

Not a problem, provided you spend a little $$ to make it legal. You'll need to add a 2P30A breaker to connect your generator to and feed the distribution panel. When you're backfeeding from your generator, you must have the main breaker shut off or open to avoid electrocuting utility folks repairing strorm damage and/or when the utility power comes back blowing up your genset. Best way and to be legal (Unless you're in Canada) is to add a Generator interlock, link attached, they're available for all distribution panels I believe. These work by mechanically assuring you can't have your genset breaker and main breaker both closed at the same time. Since you probably won't have your genset wired up all the time, a cable feeding the 30A "genset breaker" in the panel would have to be available with suitable plugs to connect to the genset. 
ITE-200A Murray Siemens ITE Generator interlock kit 150 or 200 Amp Panel Listed | eBay


To make my life easier, I cabled the genset breaker to a WP connection box on the front porch where I put the genset during outages, link attached. Cable to connect to the generator and you're done.
Power Inlet Box Cord Generator Watts Hardwire Weatherproof Outdoor Generator NEW | eBay


You mentioned 120V, if you don't have a 120/208 connector on your genset, you'll have to make up a connector with two 120V plugs to feed both sides of the 30A breaker as I don't know if you can pull the full 25A through one.


I think I spent about $150 when I did this, but it's been awhile ago. Good luck,


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## Shadetree Mechanic (Jul 13, 2017)

Thanks for the quick response. I am trying to make this as easy as possible for my wife (after I have left planet Earth). Given that, is there a specific reason to kill the Air Conditioner breaker? To me, it will sit there just fine with no effective power source (zero current flow).


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## Shadetree Mechanic (Jul 13, 2017)

Thanks much for your support. I was aware of the genset/main interlock and was considering on building my own from a bit of scrap metal. I understand that is not a good idea due to various liability issues (the overpriced store one being "listed"). The Honda, by the way, actually has a three wire 120 volt, 30 amp twist-lok output so we would be good to go on that.


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## Shadetree Mechanic (Jul 13, 2017)

By the way, are those inlet boxes weatherproof when in use?? I get driving rain here in northern Illinois...got a foot in the last ten days!! I would consider putting the inlet in my garage and letting the genset sit just outside the man door. Then again, the generator is not weatherproof either...hoot? Perhaps leave the man door open, open garage door a bit, and leave generator just inside door?


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## motormonkey (Jul 10, 2016)

SAFETY!!! 

Feeding a 240 vac circuit with 120 could have complications you don't realize. It only takes a second to turn off the breaker.

Don't jury rig an interlock. Get a proper interlock so you don't electrocute some poor utility worker.

Yes, the inlet box is waterproof. The appropriate extension cord should be too.

No, don't operate the generator in your garage. Carbon monoxide belongs OUTSIDE.

Buy the items that exmar suggested, or similar ones and see to it that they are installed and used properly.


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## exmar (Jun 29, 2015)

IMHO, rain on gensets is not a good idea, I'd put in the garage with garage door open to preclude deadly fumes entering the house.


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## motormonkey (Jul 10, 2016)

Perhaps a simple piece of plywood over the top of it.


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## thehandyman1957 (Feb 11, 2017)

Perhaps he could put it next to the garage door open about a foot with a small fan drawing in some fresh air next to it. That would keep it dry and also allow some fresh air in.


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## Jhnny321 (May 24, 2020)

Shadetree Mechanic said:


> Just got a brainstorm...would it be appropriate to tie my Honda 3000 (120 volt/30 amp) to my existing 120/240 distribution panel? I would use the single hot generator output to feed both legs of the panel input breaker. The only 240 load in the 40 circuit panel is a central air conditioner condensing unit. That unit would then receive 120 volts on both input legs, but zero volts between them. I chose the Honda for noise reasons and cannot afford one of their larger 120/240 inverter units. Please comment if you can; and thank you!.


Hi,

Just wondering if you were able to connect your smaller 120 V generator to your house panel successfully. I recently purchased a predator 3500 W quiet running generator, and want to try to do something similar as you mentioned. Though, it’s hard to find many people describing how it would be done safely, and correctly.


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## tabora (Sep 6, 2018)

Jhnny321 said:


> Just wondering if you were able to connect your smaller 120 V generator to your house panel successfully. I recently purchased a predator 3500 W quiet running generator, and want to try to do something similar as you mentioned. Though, it’s hard to find many people describing how it would be done safely, and correctly.


In order to utilize a 120V only generator safely in this way, you need to isolate the critical 120V loads you wish to run in a load center connected to one of the legs in the 240V main panel. Something similar to this: 4 Circuit Panel


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## Jhnny321 (May 24, 2020)

tabora said:


> In order to utilize a 120V only generator safely in this way, you need to isolate the critical 120V loads you wish to run in a load center connected to one of the legs in the 240V main panel. Something similar to this: 4 Circuit Panel


Hi Tabora,

Thanks for the suggestion. My electrician who recently installed a new 200 amp Eaton panel for me, suggested much the same, but said it would cost me around $1200. I was hoping to go the mechanical interlock route with an inlet box, which would be less than half that cost, but from what I understand, that option only applies to 240v generators.


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## KennyPowers (Mar 18, 2021)

per nec any stand by or portable power source ie: generator wether one or two pole 120/240v must have backfeed protection via mech interlock or transfer switch. *even backfed 120v has potential to injure / kill a lineworker or cook a running generator.


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