Portable Generator Wiring

[mityeltu]

A friend of mine asked me a question and I have no answer, so I thoughbt I'd raise it here.

He wants to install a portable generator as his backup power for his home. His plan is a little unconventional. He doesn't want to use the transfer switch I suggested. Instead he wants to trip the breakers in his breaker cabinet and then run extension cords to a receptacle on the circuit (male connections on both ends) and run the appliances that way. I don't even know if that can be done, but his questin was more about whether or not he'll burn his house down or blow up the fridge.

Can anyone answer this?

 

[tryinghard]

Yes he will burn down the house and additional to this he will electrocute family, friends, & pets. He just needs to hire an electrical contractor!

 

[roger]

Yes he will burn down the house and additional to this he will electrocute family, friends, & pets. He just needs to hire an electrical contractor!

I couldn't have said it better.

Roger

 

[ActionDave]

I agree that you should tell him "NO!".Talk to him about a main breaker interlock and a power inlet.
Not as expensive as a transfer-switch but still safe.

 

[ceb58]

Yes he will burn down the house and additional to this he will electrocute family, friends, & pets. He just needs to hire an electrical contractor!

Also ask him how he feels about prison time for involuntary manslaughter. That is what will happen if he dose it his way and kills a utility worker by back feeding the utility lines.

 

[hillbilly1]

A friend of mine leases a couple of chicken houses, and the landlord said they were ready for a portable generator if needed. My friend wanted me to set up his tractor powered generators to work with this. What the owner had done, was install a 30 amp dryer plug in the egg room where he could plug in the generator. I traced the wire back to the service panel, and found that whoever connected this, put the wires from this plug into the line side of the main! I removed those wires, and put in an interlock kit with a breaker, and changed the dryer plug to a flanged inlet in a 6x6 box. Probably saved a linemens life on that one!

 

[broadgage]

It would work, but is dangerous, foolhardy, and probably illegall, though regretably common.

An extension cord with a male plug on each end is called a suicide lead for good reason.
The main risk is electric shock, not fire.
A lead with a male plug each end is clearly dangerous if energised by utility or generator power, and the exposed pins on the other end are touched.
The scheme relies on unreliable human memorary, rather than a positive interlock, to prevent interconnection of generator power with utility lines on which men may be working.

As many others post, the best solution is a proper transfer switch that permits of generator or utility power being used, but positively prevents both being parraled or interconnected.

If the customer is unwlling to go to the expense, then cord and plug connected appliances may be unplugged from the regular outlets, and powered from generator power via suitable heavy duty extension cords.
This is the simplest answer for small generators that can only power a few appliances anyway.

A scheme popular in the UK is to install one or two branch circuits, with a manual changeover between line power and generator power. This works well for small generators and is much cheaper than a whole house transfer switch.

 

[mityeltu]

I understand the concerns and I concur. however, supposing, as he has recently indicated, that he plans on installing something akin to a kirk-key interlock on the system (jury-rigged I'm sure), is there any danger of damage to his internal wiring or equipment?

Electrically, I can't imagine it damaging anything, but I honestly have no real experience in this area. Once the system is isolated from the mains (again, this is an assumption - see above) I don't see the system as being really any different as far as electrons and impedance are concerned. Is there something else in the equation?

I have advised him in the strongest terms that this is a tragedy just waiting to happen (I have shown him arc-flash videos and shown him some horrific evidence of what happens when people are in the path to ground, as in someone stealing copper from a substation - he doesn't know that the VA ratings are vastly different), but he seems dead set (no pun intended) on it and I'd at least like to enable him to make the wisest possible choices on equipment and application to mitigate these error-likely situations as much as possible.

 

[charlie b]

Point One:
The generator will likely have a capacity that is much higher than the rating of the household receptacle into which the "widow maker" plug will be inserted. The breakers on the panel will be out of service, so there will be no overcurrent protection for that particular receptacle or for the branch circuit conductors that normally serve it. So yes, it will create a very high risk of starting a fire.

Point Two:
In your original post, you speak of powering appliances (plural) with this system. If there is an appliance that gets is power from the same branch circuit as the receptacle into which the "widow maker" will be inserted, then that appliance will have power. But since all the breakers on the main panel will be turned off, no other appliance will have power. So you would have to use two or more "widow makers," plugged into two or more receptacles, to get power to two or more appliances. But if instead he closed both the breaker to the receptacle getting powered by the generator and the breaker serving another appliance, then he will have energized the whole panel, and thus placed at risk the lives of the linemen working on restoring power to the neighborhood.

Point Three:
This is an explicit violation of NEC article 406.7(B) - 2011 NEC.

Point Four:
If he is going to run extension cords anyway, why not do the simple and obvious thing: Plug the fridge into an extension cord and run the extension cord to the generator?

 

[mityeltu]

I hadn't thought about the rating of the receptacle or OC protection. Those are both excellent points.

I think his plan was/is to trip the main, backfeed through a receptacle close to the panel and energize only selected circuits. You're right though, the branch circuit downstream from the pigtail would have no OC protection and unless he has some funky receptacles, he'll melt the thing before too long.

I looked into the mainbreaker interlocks and think I'll tell him to invest the $150 and save some lives.

Thanks guys, you might have done him and me a real favor. I live next to him and don't want my house burning down once his gets going.

 

[hillbilly1]

I'm not a big fan of Kirk key setups, but it is an effcient way to create a transferswitch, the thing with those that bother me is they are seldom used, and with that comes one or more blades not opening when breaker is "opened",if the system has not been maintained. (as with about 90% of them) I always check, but to the untrained person, this does not get done and can have disasterous consequences.

 

[SAC]

I agree with your last post - get him to look into using a main/backfeed breaker interlock system with an inlet. It is not an expensive or difficult solution if a kit is available for his panel, and is the "right" thing to do. Even if the panel is full, moving some circuits to a sub located next to the main panel isn't a big deal. For reasons posted earlier, it will be more much useful and safer. The piece of mind and additional utility is easily worth the $. Just search for "breaker interlock" and see what you can find (there are OEM and third party solutions depending on the panel).