# Backfeed Circuit Breaker



## Knucklehead_BW (Jan 9, 2012)

Hello, 

I posted a question in another thread but was advised to start my own thread. 

I am in the process of setting up my Square D circuit breaker box in my house to plug in a 5500W portable generator for power outtages. I'm going to do the usual backfeed/interlock setup. 

I have a standard Square D 2-pole 30amp 240VAC breaker assembly (two 125VAC breakers in tandem with both switches tied together). My question is, can I use this standard circuit breaker assembly as a backfeed breaker or will I need to buy a special breaker? 

thanks.


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## Julius793 (Dec 13, 2011)

Knucklehead_BW said:


> Hello,
> 
> I posted a question in another thread but was advised to start my own thread.
> 
> ...


I don't know what setup you mean but you shouldn't need special breakers. If you're back-feeding a panel you will need a breaker retainer.


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## codeone (Dec 31, 2009)

The 2 pole breaker is fine. You need the proper listed lock-out hold-down kit from square-d to have a proper installation.


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## Speedy Petey (Feb 1, 2004)

EVERYTHING you need to know is in the instructions with the interlock kit.


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## dmxtothemax (Oct 26, 2010)

I think he is concerned about the direction of current thru the breaker?
Normal would be one way,
But back feeding would be the other way, thru the breaker.

An understandable question ?

So are breakers fussed about the direction of current thru them ?

My guess would be NO !


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## Speedy Petey (Feb 1, 2004)

dmxtothemax said:


> So are breakers fussed about the direction of current thru them ?
> 
> My guess would be NO !


I know for certain it is no. A "standard" two-pole breaker is what is used.

Like I said, everything needed is included in the interlock kit, and the instructions are very clear on how to install it. 

This is of course taking into account that he is using a listed interlock kit.


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## Knucklehead_BW (Jan 9, 2012)

Thanks to all for taking the time to respond. I have considered fabricating my own interlock assembly. I tend to resist paying $150 for a kit from interlockkit.com when I have plenty of experience fabricating heavy gauge sheet metal parts. A simple pair of plates designed to allow either main breaker on or generator breaker on but not both, would be a trivial project. 

However, if I could find such a device at a reasonable price (and UL approved), I'd be inclined to buy it, just to keep the inspector happy. Are there other sources for such a kit? I could only find interlockkit.com online. 

thanks.


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## Speedy Petey (Feb 1, 2004)

I agree they are a bit steep, but if you had the kit you'd see that it is a little more than _"a simple pair of plates"_.


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## kbsparky (Sep 11, 2008)

Square D makes interlock kits for their own panels --- current models only. At about ½ the price of the aftermarkets.

If you have an older, obsolete panel, then you'll have to get one of them $150 ones.

What is the model number of your panel?


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## rjniles (Feb 5, 2007)

I doubt that an inspector would pass a home brew interlock.


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## Julius793 (Dec 13, 2011)

rjniles said:


> I doubt that an inspector would pass a home brew interlock.


You're assuming it's getting inspected


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## wavewuver (Dec 13, 2011)

I now have a new GE panel installed and bought the GE interlock kit from Home Depot. The interlock kit was less than $50 and included the sliding plate assembly and the breaker retainer. Installation of the interlock was very simple. So I can now safely back feed my panel and run my generator. I really like having the interlock kit provided by the board manufacturer.

I also have experience with the kits from the online interlokkit supplier. Their plates are very well made but their breaker retainer is kind of hokey. They provide a zip tie that is supposed to wrap around your back feed breaker as well as the opposite side breakers. The problem on the board I used to have was the breakers were so tight, you could not install the zip tie. The tie itself was simply too thick. My old board was a Murray.


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## Stubbie (Jan 7, 2007)

I'd take KBSparkys advice and see if the panel is one that Square D makes a factory interlock kit. If you can't find out and you can post the correct model number we can check for you.

There was a time when I had interlocks machined for me out of plate aluminum. That machine shop did a great job and I only had a few panels that were stubborn about accepting interlocks namely GE panels. Anyway not using a "listed" part proven and tested by a consumer product testing lab like UL does have its legal liabilities. However it's been a while since I've looked at the companies making interlocks but I believe a few companies do have UL approval whether or not UL tested them personally. The're are some small testing authorities that UL recognizes.

The only caution I would give you is if you have one custom made by one of these companies it will double the price compared to one they already list will fit a certain panel.... And you have to supply the correct measurements. If your measurements are incorrect they will not reimburse you.

Now just from experience I can tell you that most insurance companies pretty much operate on no fault policies up to a point. If your home made interlock failed to prevent backfeed to the utility and a lineman was injured or worse and upon inspection by authorities your interlock was shown to be defective ...you are going to be in a real mess.

Also most utilities and local jurisdictions *require* you to inform them that you are going to use standby generator power during an outage and they provide you with a list of acceptable means to prevent backfeed. Interlocks are not always acceptable. 

So my point is what sometimes looks simple is not so simple ....


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## Knucklehead_BW (Jan 9, 2012)

Thanks to all for your responses. As for the model number of this unit, I'm not sure what to tell you! The panel door has a label with about a zillion numbers, and so does the box. So, here goes. 
Panel door label: Square D Homeline Cat number HOMC20U100C. Series S01. Type 1 enclosure. Two more numbers: 033341. 40265-626-04. 
Box: Issue number V-2813. 40265-543-01. Cat number BXH26B1K (I think...). 

Whew! 

Anyway, if Square D or some other manufacturer makes a reasonably priced interlock kit, please let me know. Stubbie, thanks for the info about most local utilities and jurisdictions requiring notification about this. Sounds like this is my next step before I invest in something that may or may not be usable. 

thanks to all, again, for your help.


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## Kene115 (Sep 24, 2021)

Knucklehead_BW said:


> Thanks to all for taking the time to respond. I have considered fabricating my own interlock assembly. I tend to resist paying $150 for a kit from interlockkit.com when I have plenty of experience fabricating heavy gauge sheet metal parts. A simple pair of plates designed to allow either main breaker on or generator breaker on but not both, would be a trivial project.
> 
> However, if I could find such a device at a reasonable price (and UL approved), I'd be inclined to buy it, just to keep the inspector happy. Are there other sources for such a kit? I could only find interlockkit.com online.
> 
> thanks.


I had the same concern about the high price plus high freight. When I received the Interlock kit I was very impressed by the quality and with the way the slide mechanism works. I ordered a second one for a neighbor that saw mine. Still pretty pricy.


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## Jim Port (Sep 21, 2007)

I hope they solved this 9 years ago.


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