generator question

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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I had a rather long and drawn out exchange with some people recently that have a rather odd installation issue.

They have an attached garage with a subpanel in it that they had a transfer switch installed so they can hook up a generator thru a cord.

The first time I read this I said there is just no way to back feed the generator into the garage panel "legally", or safely for that matter. You would have to install the transfer switch at the service point to switch out the utility power and switch in the generator. I gather the expense involved makes this unpalatable, given it is already installed.

An electrician is suggesting some kind of "lost key" system that is made by someone that is allegedly UL listed and backed up by a PE sealed letter where there is some kind of key in the service panel that can only be removed when the main is off, and can be used to turn on the back fed breaker in the garage. Anyone ever heard of such a thing? It just seems convoluted for a residential system.

Does the code even allow for something like this in lieu of a real transfer switch?

I usually just stay out of the threads about generators there because the usual wisdom involves a suicide cord and the dryer outlet. But this one caught my eye because it was so unusual.
 
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iwire

Moderator
Staff member
Location
Massachusetts
We often call it a 'Kirk Key' http://www.kirkkey.com/default.aspx?Page=Products system and it is used in many commercial installations.

In it's basic form locks are installed at two breakers, neither breaker can be closed without the key inserted and the key cannot be removed with the breaker closed so it becomes impossible to close both breakers at the same time without resorting to removing the hardware which can be done.

I doubt any AHJ is going to buy into it at a dwelling unit.
 

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Engineering
We often call it a 'Kirk Key' http://www.kirkkey.com/default.aspx?Page=Products system and it is used in many commercial installations.

In it's basic form locks are installed at two breakers, neither breaker can be closed without the key inserted and the key cannot be removed with the breaker closed so it becomes impossible to close both breakers at the same time without resorting to removing the hardware which can be done.

I doubt any AHJ is going to buy into it at a dwelling unit.

Iwire,
I agree it can be defeated but can the AHJ reject it for what someone could or may do later?
 

iwire

Moderator
Staff member
Location
Massachusetts
I agree it can be defeated but can the AHJ reject it for what someone could or may do later?

702.5 Transfer Equipment. Transfer equipment shall be
suitable for the intended use ...........

The AHJ gets to decide if it is suitable.

In my personal opinion a Kirk key system is intended for qualified personal, not HOs.

But it would be up to the AHJ not me. :)
 

stew

Senior Member
no reason i can see that if the subpanel has a main breaker that is fed from the main panel that it cant be safely interlocked and a generator safely connected to those loads. If there is not a main maybe a backfed main can be added and then an interlock installed. If not rplace the panel with one that can be interlocked.
 

stew

Senior Member
i thought they only wanted to feed the sub. my mistake. if thats what they want to do then no not possible safely. only read in his post that he wants to feed the sub safely and if it has a transfer switch then I see no problem.I dont see anywhere in his post that he wants to backfeed the main. hmmmm?
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
i thought they only wanted to feed the sub. my mistake. if thats what they want to do then no not possible safely. only read in his post that he wants to feed the sub safely and if it has a transfer switch then I see no problem.I dont see anywhere in his post that he wants to backfeed the main. hmmmm?

pretty much by definition the garage panel is going to back feed the main penal when the generator is plugged into the garage panel unless the garage main is turned off. they want to backfeed the whole house through the garage panel.

I just found the whole exchange odd and his electrician's solution unusual.

Having read art. 702 again, I think it does allow for this kind of solution. It does not actually require a switch per 702.6. Just that it be "suitable". I am not convinced that this kind of solution is suitable for a residence, but as someone mentioned, it would be up to the AHJ.

My guess is they find out what it costs and go the suicide cord route.
 

stew

Senior Member
i did not see and still dont see anywhere in the original post that they wanted to feed the main panel. obviosly they cant do that safely without a kirk key.even then in my opinion with a homeowner its iffy.
 

Smart $

Esteemed Member
Location
Ohio
i did not see and still dont see anywhere in the original post that they wanted to feed the main panel. ...
I don't either. If they had a transfer switch installed, exactly how is it connected? I don't see how you have a transfer switch and also backfeed the subpanel?
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
Even if a kirk key set up was used, it would have to be installed on the generator back feed breaker, not the garage panel main. Doubt any AHJ would pass it on residential.
 

stew

Senior Member
if there is a transfer device in this subpanel as apparently described in the original post then the subpanel main breaker will have to be turned off for the generator backfeed breaker to be energized to then feed the sub from the generator. With the main in the sub turned off there is of course no backfeed to the main panel thus making this a perfectly acceptable generator setup if all that is going to be run are the circuits in the sub. I still see no problem at all with this. Now if in fact the customer does want the main to be energized therin lies a problem.
 

TobyD

Senior Member
What type or brand name panel do you have?Siemens has a main to breaker kit lock out.They also have a siamese type kit to lock in or out two breakers opposed to each other.Seems like a ATF would be the safest.
 

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Engineering
I had a rather long and drawn out exchange with some people recently that have a rather odd installation issue.

They have an attached garage with a subpanel in it that they had a transfer switch installed so they can hook up a generator thru a cord.

The first time I read this I said there is just no way to back feed the generator into the garage panel "legally", or safely for that matter. You would have to install the transfer switch at the service point to switch out the utility power and switch in the generator. I gather the expense involved makes this unpalatable, given it is already installed.

An electrician is suggesting some kind of "lost key" system that is made by someone that is allegedly UL listed and backed up by a PE sealed letter where there is some kind of key in the service panel that can only be removed when the main is off, and can be used to turn on the back fed breaker in the garage. Anyone ever heard of such a thing? It just seems convoluted for a residential system.

Does the code even allow for something like this in lieu of a real transfer switch?

I usually just stay out of the threads about generators there because the usual wisdom involves a suicide cord and the dryer outlet. But this one caught my eye because it was so unusual.

I do not see how this could work.

"They have an attached garage with a subpanel in it that they had a transfer switch installed so they can hook up a generator thru a cord. "

Why even use an MTS? wouldn't it have to be in front of the sub panel in order to backfeed into the main panel?
If not the MTS is useless. It sounds like the MTS is fed from a breaker in the subpanel and then back in to the sub panel on another breaker. Generator feeds emergency side of MTS. You still have to kill the main in the house and that is where the Kirk Key comes in. Turn off the main in the house, take out the key and go to the garage and turn on the breaker fed by the generator.
Just thinking out loud, Tell me if my thinkin is wrong.......
 
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