800 amp Feeder

[Killerwatt70]

On a current project we have uncovered a feeder that leaves the switchgear as 2 sets of 4/600kcmils with a #1 grounding conductor. Enters a junction box on it's routing where they used clear taps, and it switches to 3 sets of 3/300kcmils with a #2 that was changed from grounding conductor to grounded (neutral) conductor. In the junction box with the clear taps, all of the conductors of that phase are landed on this.
This feeder needs to be rerouted around a vertical shaft. And we definitely want to bring it up to code but really have been caught off guard with the setup.
Is it to code already? Is this a common practice? I have been in the industrial field for almost 30 years and never ran across a setup like this. Any input would be helpful.

 

[Dennis Alwon]

Without a book I am guessing that the #1 and #2 equipment grounding conductor's are too small.

 

[kwired]

Without a book I am guessing that the #1 and #2 equipment grounding conductor's are too small.

Correct, it needs to be 1/0 copper or 3/0 aluminum for 800 amps OCPD.

I was thinking maybe the original install was a EGC then later someone decided they needed a neutral and was acceptable to use metal raceway for the EGC, which can be acceptable, but even in that situation the neutral needs to be no smaller than the minimum required EGC if it is a feeder circuit.

 

[electrofelon]

What is a "clear tap"?

 

[kwired]

What is a "clear tap"?

Burndy's version of a Polaris tap is clear insulating material.

I think Ilsco has clear ones also.

 

[electrofelon]

Burndy's version of a Polaris tap is clear insulating material.

I think Ilsco has clear ones also.

Ah ok, thought it was some term or method I'd never heard of. Yeah I like those. Nice to see the connection.

 

[Killerwatt70]

Thanks
I was aware of the sizing on the ground.
I was thinking more about the conductors per phase, and sizing changes, as well as the way they terminated all to 1 clear tap per phase.
I have always thought regardless of the size of a circuit, splices on parallel conductors were still treated separately, and should remain the same size and/or amount of conductors.

 

[augie47]

IMO, with your cleartap the paralleling of the 600s stops at the clear tap and a new set of parallel conductors can be picked up there to their termination as long as the ampacity of the 2nd set is not less than the OCP device or meet the tap rule.

Don't know the details but an example might be where they have been using the 600s to address voltage drop and the 350s are short enough not to cause a problem.

 

[kwired]

IMO, with your cleartap the paralleling of the 600s stops at the clear tap and a new set of parallel conductors can be picked up there to their termination as long as the ampacity of the 2nd set is not less than the OCP device or meet the tap rule.

Don't know the details but an example might be where they have been using the 600s to address voltage drop and the 350s are short enough not to cause a problem.

I agree. First set of 600's is a set that makes up an overall higher ampacity conductor. Those elements of that set must have same characteristics so that they all have equal impedance in order for current to balance between them, if one has a lower impedance it will carry more current than the others, if it is too low it may carry more than it is individually rated to carry, and that is not good for insulation on that conductor, or even possibly for heating effects at terminations.

Now once you splice (like at your clear taps) and then continue the run, you start over with a new segment of conductor - it can be a single conductor or multiple smaller conductors selected to create one effectively larger conductor. Can even switch from copper to aluminum. Key is each segment of the system must have minimum required ampacity and proper overcurrent protection.

A larger size for voltage drop then reducing to smaller size for terminations (at either end) can be common with long runs where voltage drop is an issue.

 

[Killerwatt70]

I appreciate each of your responses and clarification with this.
The run is only about 300' and we could not come up with any reasoning behind what we found.
Nor have any of us ever seen taps like this before changing configurations, or each conductor splicing all together and continuing in a junction box. I think that was really the most confusing part.
Growing concerns with it being a hospital and of course inspections etc.
Thanks again

 

[kwired]

I appreciate each of your responses and clarification with this.
The run is only about 300' and we could not come up with any reasoning behind what we found.
Nor have any of us ever seen taps like this before changing configurations, or each conductor splicing all together and continuing in a junction box. I think that was really the most confusing part.
Growing concerns with it being a hospital and of course inspections etc.
Thanks again

One common application where you might see splicing in such a feeder is where taps are made from the feeder.

A sort of common misconception for tap installations to parallel conductors is to make taps that don't connect to all conductors of the parallel set.