Is this tap legal?

[Tainted]

There are 3 phases that feed the bus bars of a panel as shown in picture below. The left and middle phases are tapped. The right phase is not tapped.

Is there anything in the code that prevents us from tapping this bus? I've heard that it might be illegal because it can cause unbalance of the feeders.

 

[infinity]

About the only thing that would make it illegal is if it compromised the existing bus by drilling a hole. And who knows maybe those were factory holes. Since that's a 1/4" screw I wouldn't worry about it. Any imbalance would need to be part of a load calculation.

 

[Tainted]

About the only thing that would make it illegal is if it compromised the existing bus by drilling a hole. And who knows maybe those were factory holes. Since that's a 1/4" screw I wouldn't worry about it. Any imbalance would need to be part of a load calculation.

Might be drilled, the nuts do not really look like they are centered

 

[Birken Vogt]

Well copper chips are laying all over

Still I would not lose a minute of sleep over it

 

[Ohm2]

I agree with the others. Concerns would be load balancing, possible length of those taps, OCPD.

 

[Ohm2]

Well copper chips are laying all over

Still I would not lose a minute of sleep over it

good eye

 

[Tainted]

Well copper chips are laying all over

Still I would not lose a minute of sleep over it

You sir are a good detective!

 

[jim dungar]

I've heard that it might be illegal because it can cause unbalance of the feeders.

If this was illegal, due to imbalance, we would never be allowed to connect single phase loads to three phase feeders.

It would be a problem if the tap was made to only one buss in a parallel aet.

 

[ggunn]

Might be drilled, the nuts do not really look like they are centered

I hope the bus was de-energized when the holes were drilled.

 

[wwhitney]

The distance between the lug on the middle busbar and the left busbar is clearly less than the distance between the busbars. I would think that may be a problem and that the lug should be rotated not to overhang the middle busbar.

Cheers, Wayne

 

[infinity]

The distance between the lug on the middle busbar and the left busbar is clearly less than the distance between the busbars. I would think that may be a problem and that the lug could be rotated not to overhang the middle busbar.

What is the minimum required distance for 208 volts? Looks like it's been there for a very long time without any issue.

 

[wwhitney]

What is the minimum required distance for 208 volts? Looks like it's been there for a very long time without any issue.

I don't know, and one could research that and maybe figure out that it's OK. But the manufacturer picked a distance between the busses for a reason, and the obvious way to make a change like adding those lugs is to maintain that distance so you don't have to do that research.

Cheers, Wayne

 

[infinity]

I don't know, and one could research that and maybe figure out that it's OK. But the manufacturer picked a distance between the busses for a reason, and the obvious way to make a change like adding those lugs is to maintain that distance so you don't have to do that research.

Cheers, Wayne

Also the lug is offset so the distance may be the same. Hard to tell from the photo.

 

[wwhitney]

Also the lug is offset so the distance may be the same. Hard to tell from the photo.

It is obvious from the picture that the distance is less. The offset out of plane is less than the lug projects to the left. And even if it were the same, that would result in a shorter distance to the corner of the left hand busbar.

Cheers, Wayne

 

[winnie]

The distance between the lug on the middle busbar and the left busbar is clearly less than the distance between the busbars. I would think that may be a problem and that the lug should be rotated not to overhang the middle busbar.

Cheers, Wayne

1) IMHO that is a good idea and should have been considered when the lug was initially installed.

2) The the manufacturer probably uses the same bus bar spacing for everything up to 600V, and this is likely not a problem.

-Jonathan

 

[infinity]

The the manufacturer probably uses the same bus bar spacing for everything up to 600V, and this is likely not a problem.

I think that you're correct. For old 208 volt bolt-on panels they have stabs that accommodate 1" wide breakers so the stabs are typically less than 1/2" apart.

 

[NoahsArc]

I hope the bus was de-energized when the holes were drilled.

We've lost guys when it wasn't. Never drill into live switch gear - shouldn't be an issue in the 21st century, but it is.

 

[Seven-Delta-FortyOne]

There are some panelboards/switchgear that the manufacturer states that the bars may not be drilled, so that would create a 110.3(B) violation.

I was talking to a buddy of mine the other day, and they had to disassemble a giant piece of switchgear to get it into the basement, and they had to call out a factory rep to check and make sure the bolts were torqued properly after reassembly.

 

[ggunn]

Is there any reason why the listing of the equipment might be invalidated by drilling new holes in the busbars? I have seen clamp-on type lugs advertised on line that do not require drilling holes in a bus.

 

[Fred B]

About the only thing that would make it illegal is if it compromised the existing bus by drilling a hole. And who knows maybe those were factory holes. Since that's a 1/4" screw I wouldn't worry about it. Any imbalance would need to be part of a load calculation.

Is there a minimum TPI for attaching screws / bolts on a bus connection like referenced for a receptacle/switch of 32TPI?