National electrical Code Tap rule

[GordonT]

I am interested in obtaining input to whether a tap of a bus in a switchboard, panelboard is permitted by the NEC. In looking through the code recently I could not find this although I have seen it done on numerous occasions.

 

[dpc]

2002 NEC Article 240.21.B - Feeder Taps. (It's long)

Short answer: Yes, taps are allowed under certain conditions. There are different rules depending on length of tap.

 

[peebee]

The problem is UL, not NEC. Drilling holes in your bus will irreversibly violate the UL listing.

 

[GordonT]

My problem is that the NEC while allowing taps of feeders and busways does not discuss the tapping of switchboards or panels etc. At least not based upon my review to date. I know it is frequently done under the various "tap rule" provisions but I was surprised when a local code official raised objection. We have since obtained re-certification from the switchboard manufacturer so the situation is resolved. Thanks to dpc and peebee for replying.

 

[peebee]

Sweet.

Just curious, whose board was it? I was recently asked to explore recertification of two boards that had been similarly raped by a contractor, and both manufacturers (GE and Cutler-Hammer) declined to repair or recertify.

 

[dpc]

If you're talking about physically drilling into the bus, then peebee is correct, this is not generally allowed.

Most panelboard suppliers can provide "sub-feed" and "through-feed" lug kits that will accomplish the same thing and allow you to keep your rating. The sub-feed kits are available only for main lugs only panels.

Another option is to use "gutter taps". You can use split-bolt or other types of connectors to tap the incoming **cable** not the bus. This is allowed by NEC and UL, provided you have enough room in the gutter or wireway.

Of course, the local inspector gets the last word...

 

[GordonT]

It was a GE board and we used holes that were already there for 2 future 400A breakers. We haven't recived the written re-certifcation yet but the GE inspector did not have any issue with what was done.

 

[dpc]

You are well outside the realm of science or even logic when you get into UL and code issues. I've found it doesn't pay to spend too much time on these "code lawyer" issues if there is another solution at hand.

Look at it from GE's perspective - what is in it for them, besides increased liability should this panel cause someone an injury, for any reason, in the next 40 years?

Good luck, and consider bringing in some doughnuts for your local inspector.