generator tap box

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jrvazzer

Member
Can someone help me. A generator tap box is located for the purpose of bringing a Food Store to life again after a storm. So rather than renting a portable gen and runing cables all over the floor back to the main board disconnecting the mains and connecting the generator cables. This box is already connected to the main board via taps and all the genrator company have to do is plug into the tap box near the loading doc with camlocks and open the main brker and away she blows.
The question is can you connect the conductor via conduit say 100' right to the main board without a disconnect means?
The main board is rated 2500A the conductors for the generator tap box is 800A. The tap box is kirk key with the MCB at the board.
This feeder is only used when their is a power failure the rest of the time is connectd hot to the tap box.
 

RUWired

Senior Member
Location
Pa.
The question is can you connect the conductor via conduit say 100' right to the main board without a disconnect means?

No, you would not be able to connect the conductors directly to the main switchboard without an OC protection device. You will have to follow the rules for tap conductors in 240.21(B)(1) or (2).

Rick
 

BAHTAH

Senior Member
Location
United States
Generator Tap Box Conection

Generator Tap Box Conection

As stated you cannot run from the generator to the switchboard without overcurrent protection. From what you stated, you have the tap box connected to the switchboard via the 800amp breaker and the Kirk Key interock only allowes either the MCB or the 800 Amp breaker to be closed, but not both. Typically the generator will have a main breaker to protect the conductors from the generator to the tap box and the switchboard.
 

jrvazzer

Member
generator tap box

As stated you cannot run from the generator to the switchboard without overcurrent protection. From what you stated, you have the tap box connected to the switchboard via the 800amp breaker and the Kirk Key interock only allowes either the MCB or the 800 Amp breaker to be closed, but not both. Typically the generator will have a main breaker to protect the conductors from the generator to the tap box and the switchboard.

Why does it need ocp at the main board? These conductors are only backfeeding the Main board. The Generator tap box can only be activated when the main ckt. beakers is off. The generator is only 600 Amps.
 

jrvazzer

Member
Generator Tap box

Generator Tap box

No, you would not be able to connect the conductors directly to the main switchboard without an OC protection device. You will have to follow the rules for tap conductors in 240.21(B)(1) or (2).

Rick

Why does it need ocp at the main board? These conductors are only backfeeding the Main board. The Generator tap box can only be activated when the main ckt. beakers is off. The generator is only 600 Amps
 

kwired

Electron manager
Location
NE Nebraska
Why does it need ocp at the main board? These conductors are only backfeeding the Main board. The Generator tap box can only be activated when the main ckt. beakers is off. The generator is only 600 Amps
I don't see that it does need OCP at the main board. Just a switch with no OCP should be sufficient. The conductors need OCP at the supply end.
 

iwire

Moderator
Staff member
Location
Massachusetts
Considering you often have little control over the size of the overcurrent device on the generator that you rent in an emergency I think it is more than prudent to install overcurent protection at the gear that has a setting less than the rating of the conductors to and the tap box itself.
 

RUWired

Senior Member
Location
Pa.
Why does it need ocp at the main board? These conductors are only backfeeding the Main board. The Generator tap box can only be activated when the main ckt. beakers is off. The generator is only 600 Amps

The way i see it is the conductors are tapped at the switch board, and are energized from the bus bar untill interlocked out. There would'nt be any short circuit protection on the conductors while in the normal condition.

Rick
 

iwire

Moderator
Staff member
Location
Massachusetts
The way i see it is the conductors are tapped at the switch board, and are energized from the bus bar untill interlocked out. There would'nt be any short circuit protection on the conductors while in the normal condition.

Rick

Because of the kirk key set up it should be impossible to feed the tap box from the utility.
 

RUWired

Senior Member
Location
Pa.
Because of the kirk key set up it should be impossible to feed the tap box from the utility.
Unless i'm missing something in the OP,the tapped conductors are still energized up to the tap box located 100' plus away. The kirk key opens the main breaker on the switch board, then allows the closing of the tap box breaker/ enclosure from the generator source.

Rick
 

iwire

Moderator
Staff member
Location
Massachusetts
Unless i'm missing something in the OP,the tapped conductors are still energized up to the tap box located 100' plus away. The kirk key opens the main breaker on the switch board, then allows the closing of the tap box breaker/ enclosure from the generator source.

Rick

If it is designed as it should be you cannot close the main breaker without inserting the Kirk key and you can't take the kirk key out of the tap box breaker without opening the breaker.

In other words the kirk key prohibits both breakers from being closed at the same time.

If it is not set up like this the kirk key is worthless.
 

Smart $

Esteemed Member
Location
Ohio
If it is designed as it should be you cannot close the main breaker without inserting the Kirk key and you can't take the kirk key out of the tap box breaker without opening the breaker.

In other words the kirk key prohibits both breakers from being closed at the same time.

If it is not set up like this the kirk key is worthless.
It sounds like their is no tap box breaker... rather the kirk key provides access to the tap box.

I agree that it would be prudent to include ocp. The connected generator may have ocp exceeding the tap ampacity rating.
 

jrvazzer

Member
generator tap box

Unless i'm missing something in the OP,the tapped conductors are still energized up to the tap box located 100' plus away. The kirk key opens the main breaker on the switch board, then allows the closing of the tap box breaker/ enclosure from the generator source.

Rick

Yes, but just to make it clear for everyone. The tap box is just a hugh box with camlocks access cover, so the generator would be connected. Don't mean to beat a dead horse but some have the opinion that the main board should have a ocp and some don't, because of the Kirk key arrangement. I kind of feel the same way. but one has fully convince me of either? I would prefer to install the ocp if the capacity at the board was available , but I don't. And also not in the budget.
I want to simply tap the main board with 2 sets of 600mcm directly to the generator tap box. with kirk keys. Yes or no?
Thanks,
 

jrvazzer

Member
The way i see it is the conductors are tapped at the switch board, and are energized from the bus bar untill interlocked out. There would'nt be any short circuit protection on the conductors while in the normal condition.

Rick

Yes, the normal condition the tapbox would be hot, but no one can gain access unless the main beakers is off and the tap box cover is open.
 

kwired

Electron manager
Location
NE Nebraska
Are you referring the Generator c/b?

I am talking about the back fed switch you described in the main switchboard, at least that is what I understood you to have. I also understand that it is interlocked so that it can not be turned on if the main is on and the main can not be turned on if the generator switch is on. If I have this wrong I may take back what I said.
 

iwire

Moderator
Staff member
Location
Massachusetts
It sounds like their is no tap box breaker... rather the kirk key provides access to the tap box.

OK, thanks.

I have never seen it set up that way and it does not impress me, but of course who am I to be impressed.

If that is the case I see no legal way short of concrete encasement to tap a 2500 amp bus with 800 amp conductors and no OCPD at the bus.
 

iwire

Moderator
Staff member
Location
Massachusetts
Yes, the normal condition the tapbox would be hot, but no one can gain access unless the main beakers is off and the tap box cover is open.

In my opinion regardless of anyone having access to it or not because these are hot from the utility under normal conditions the supply end of the conductors need a OCPD or they have to meet the tap rules in 240.21.
 

RUWired

Senior Member
Location
Pa.
I want to simply tap the main board with 2 sets of 600mcm directly to the generator tap box. with kirk keys. Yes or no?
Thanks,

I still stand with the idea that an OCPD is required because you are making a tap with conductors rated smaller than the main breaker that will be energized untill locked out. Haveing the kirk key interlock protects the personel upstream.
Rick
 
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