TAP RULE

[Canton]

I have to feed some external sub-metering equipment from our 480 gear. I need a 3 pole 30 amp feed to this equipment. It has to be feed from this gear because the current readings and voltage must be from the same source. I have no available space for a small breaker and the gear is full.

I want to make a tap inside the gear to feed this equipment off the 2000 amp bus. Applying the 10' tap rule and using a tap conductor with 1/10 the ampacity would make a really big tap conductor for a 30 amp feed. If I fuse the TAP conductor before it leaves the gear am I still required to use that large of a conductor?

 

[Glennsparky]

Looks like everyones asleep. So, IMHO a 30A conductor is appropriate after a 30A fuse. It is no longer a tap. Just watch out for fill and listing violations. Good luck.

 

[Canton]

Looks like everyones asleep. So, IMHO a 30A conductor is appropriate after a 30A fuse. It is no longer a tap. Just watch out for fill and listing violations. Good luck.

Its the tap that I am questioning. The size of the conductor to the gear's buss? If I fuse the tap before it leaves the gear am I required to size it for 1/10 the ampacity of the buss (2000amps/200amps)? 200 Amp conductor is huge for only needing a 30 amp feed. I was thinking if it were fused before leaving the gear i could use 10 to the gears buss;

 

[Glennsparky]

Oh, I get it. The 1/10 rule only applies when the "... tap conductors leave the enclosure or vault in which the tap is made ..." 2008 code 240.21(B)(1)(4). A 30A conductor ahead of the fuse should be fine.

 

[augie47]

I agree, the 1/10 is for conductors that "leave the enclosure", however, in regard to your fuses, keep 240.40 in mind.

 

[kwired]

I agree, the 1/10 is for conductors that "leave the enclosure", however, in regard to your fuses, keep 240.40 in mind.

Also keep 240.24(A) in mind - in particular "Overcurrent devices shall be readily accessible".

 

[Canton]

Thanks for the info!

 

[infinity]

Is this 2000 amp gear service equipment? If so line side taps wouldn't have to comply with the tap rules in Article 240.

 

[Canton]

Is this 2000 amp gear service equipment? If so line side taps wouldn't have to comply with the tap rules in Article 240.

Hey Rob, thanks for the info. Yes it is service equipment, but we are doing the tap on the load side. I was not sure if the tap had to follow the requirements if it did not leave the gear. We are going to put a pullable fuse block in one of the cabinets.

 

[kwired]

Hey Rob, thanks for the info. Yes it is service equipment, but we are doing the tap on the load side. I was not sure if the tap had to follow the requirements if it did not leave the gear. We are going to put a pullable fuse block in one of the cabinets.

Consider what kind of arc flash hazard there may be if changing these fuses as well.