Feeder tap size transition versus tap from a tap

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xguard

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Baton Rouge, LA
I have a 3 pole 800 AMP circuit breaker disconnect I'd like to tap. I'd like to feed a 100 AMP Circuit breaker disconnect with this tap.

The 800 AMP disconnect has lugs (3 lugs per pole, the other two lugs per pole are for a parallel 600 MCM feeder) that are rated for a minimum 500 MCM conductor. The largest conductor allowed on the 100 AMP Disconnect I'd like to connect this tap to is 1 AWG.

The 500 MCM is as protected as a tap on the 800 A disconnect, if I transition to 1 AWG at the 100 AMP disconnect and the combined length of the 500 MCM and 1 AWG is not more than 10 feet, is this considered a tap from a tap? The combined 10 foot 500MCM/1 AWG section would be protected in accordance with the 1 AWG tap ampacity requirments, 130 AMPS / 800 AMPS greater than 10%.

Thanks for any feedback!
 
Hmmm... that's a good question. If I were the AHJ, I would permit it. But I am not... and afraid there may be those that would not. Proceeding from the 'would not' perspective, let's see if there is an alternative...

You mentioned 3 lugs per pole. Is that truly 3 lugs per pole or is it one 3-hole lug per pole? The reason I ask for this distinction is because, if it is three separate lugs per pole, you should be able to just replace one per pole with another sized for 1AWG.

Did you check to see if the conductor holes are rated for two conductors... and their size?
 
On the 800 AMP Breaker each Lug (one lug per pole) has 3 holes, each hole is rated for 1 500MCM-750MCM. At least from what I can get from the instruction manual and the tech on the phone. I hope I'm using the word lug correctly.
 
xguard said:
On the 800 AMP Breaker each Lug (one lug per pole) has 3 holes, each hole is rated for 1 500MCM-750MCM. At least from what I can get from the instruction manual and the tech on the phone. I hope I'm using the word lug correctly.
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Yes, you are using the word lug correctly. To be more precise, each is a 3-hole mechanical lug.

Can you run it by your AHJ?

I'd make the transition as close as possible to the 800A breaker, using a Burndy Y342CR reducing sleeve (500MCM-2AWG) with mating YS34 compression butt splice (500MCM), or equivalent. Note 2AWG should meet your needs.

I know that may present a challenge if you're using 600MCM for the other conductors, but Burndy doesn't list a reducing sleeve for 600MCM butt splice... but the catalog says contact technical support for other sizes not listed.

http://ecat.burndy.com/Comergent/en...e=SingleLevelCategory&catKey=603108##false
 
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I would also agree that this is not a tap of a tap.

My reasoning is that these conductors, from end to end (from the 800A breaker to the 100A breaker) treated as a single entity, meet the rules of a tap conductor. The fact that there is a size change in the middle of this tap conductor is in my mind the same as having a change from tap conductor to lug to bolt to breaker.

An approach that you might use, if the AHJ does not buy this argument, is to use something like a 'pin adapter' shown on page 27 of http://www.greaves-usa.com/pdfs/pp20-37 Compression.pdf They don't list the size combination that you need, but you can contact them.

If you are calling for a 'special' you might also ask if they can do an 'increasing' pin adapter, one that would connect your 1AWG conductor into the 500 kcmil lug. That way you only have to maneuver the 1AWG conductors around in your housing. They have some interesting devices (see page 32) designed to adapt smaller wires into larger crimp connections.

This is, of course, simply using a compression connector to splice from the larger wire to the smaller wire...but as a separate listed device rather than as a length of wire.

-Jon
 
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