Tapping busbar to get an extra circuit

[clovingood]

I'm confused a bit here at work. The electrical engineer thought we could add another 225amp breaker to feed another load center. I told him we could not do that because there is no more space availible in the main distribution panel. The Main distribution breaker is 1200amp, 120/208volts. He suggested to tap the bus bars to provide a stand off breaker box to feed the new load center.

If we tap the bus bar, wouldn't we be breaking NEC code, such as UL listing? Anybody with experience tapping off a bus bar that can give me some advice? I would really appreciate it. Thanks.

r,

Chris

 

[Dennis Alwon]

I have heard that done however it does seem to be a violation of 110.3- listing & labeling.

 

[dkidd]

Here is a UL statement on this in

http://www.ul.com/global/documents/...newsletters/electricalconnections/april10.pdf

 

[ron]

If there is room in the cable entry area of the panel, you could tap the incoming conductors and follow the tap rule limitations. That way you are not modifying the bus bars.

 

[Cow]

You have to get a letter from the manufacturer stating it's OK to do this first. And then be able to show the inspector when he asks for it.

We just had to do this to an old piece of Siemens gear they didn't make GFI breakers for, we had to tap the buss and add a standalone GFI breaker enclosure.

 

[petersonra]

Is there lug space available somewhere?

Might be feed thru lugs you could use.

 

[clovingood]

You have to get a letter from the manufacturer stating it's OK to do this first. And then be able to show the inspector when he asks for it.

We just had to do this to an old piece of Siemens gear they didn't make GFI breakers for, we had to tap the buss and add a standalone GFI breaker enclosure.

Cow,

I'm a Federal electrician on the Navy base here in San Diego. We don't have inspectors, basically we do whatever the hell works as far as I've seen since working here. Just to let you know, I am licensed. But my fellow electrician on the Navy base told me they don't have too. Anyways....

Electrical engineer wants to do exactly what you said. It is an old General Electrical Main Distribution Panel. We have decided to tap off the bus bar and put a standalone box with a 225amp breaker.

r,

Chris

 

[clovingood]

If there is room in the cable entry area of the panel, you could tap the incoming conductors and follow the tap rule limitations. That way you are not modifying the bus bars.

There is plenty of room for more wires in the main distribution panel. Hopefully there are some pre-drilled holes on each of the phases. We are considering putting some lugs of each phase to put a stand along box with a 225amp circuit. The box will be within the 10'ft. rule.

r,

Chris

 

[clovingood]

Here is a UL statement on this in

http://www.ul.com/global/documents/...newsletters/electricalconnections/april10.pdf

Yes, I have read that. Thanks. I have mentioned it to the Electrical supervisor on the Navy PWC, and he told me they do it all the time. Since the main distribution panel is pretty old (G.E., probably 1960s) we are going to tap the bus bar and put a stand alone break box with a 3-pole 225amp breaker. The break box is to supply an electrical car charger station.

Thank you for your help. It feels great to talking to people who know what they are talking about.

r,

Chris

 

[cadpoint]

Buried in the Code is the requirement to know of the total load summary for that existing service! There's your factor for consideration.

Knowing of the Navy they didn't go short or small! The proof is in the numbers...

 

[kwired]

Cow,

I'm a Federal electrician on the Navy base here in San Diego. We don't have inspectors, basically we do whatever the hell works as far as I've seen since working here. Just to let you know, I am licensed. But my fellow electrician on the Navy base told me they don't have too. Anyways....

Electrical engineer wants to do exactly what you said. It is an old General Electrical Main Distribution Panel. We have decided to tap off the bus bar and put a standalone box with a 225amp breaker.

r,

Chris

Doesn't the engineer directing you to do this put most of any liability issue on him should it be a problem? Make sure you have documentation that he approved it. You should also have him provide instructions of exactly how to do it.

 

[weressl]

Cow,

I'm a Federal electrician on the Navy base here in San Diego. We don't have inspectors, basically we do whatever the hell works as far as I've seen since working here. Just to let you know, I am licensed. But my fellow electrician on the Navy base told me they don't have too. Anyways....

Electrical engineer wants to do exactly what you said. It is an old General Electrical Main Distribution Panel. We have decided to tap off the bus bar and put a standalone box with a 225amp breaker.

r,

Chris

Evidently the 'Federal' automatically qualifies one to override the rules of physics or manufacturers installation instructions.hmy:

The other one I also like: we do it this way all the time.....:happyno:

 

[jimnan88]

If this is a large panel the buss bar is generally suspended and you have lots of access to it. If you have no other choice but to drill drill at the very end after the other loads. If you can there are clamping lugs you can use that don't require drilling.
The issue is removing cross sectional area when you drill and creating a hot spot or an overloaded area in your bus bar.
I could figure out a way in a large panelboard to add it.
Also this is not unusual it happens.