Are reducing splices allowed on tap feeder conductors to fit on the equipment?

J

jnava

Member
Location
Massachusetts
Are you allowed to install a reducing splice at the end of a feeder tap, so it fits on the equipment disconnect terminals? It appears to me that regardless of the tap length, it is not allowed. Thoughts?
 
I think it is allowed for 10ft taps, possibly not for 25ft and other taps. A splice to me is just an extension of tap conductors. (Where exactly does it say you can't tap a tap?)
 
For taps over 25 foot long, 240.21(B)(4)(6) specifically says the tap conductors must be continuous from end-to-end and contain no splices...so that's clear. However it does not specifically say that for the not over 25' tap or 10' tap.
 
Why would a tap conductor be larger than required for the equipment? IOW's, a tap is usually a smaller conductor.
I'm not saying there's not a reason, just curious.
 
jnava said:
For taps over 25 foot long, 240.21(B)(4)(6) specifically says the tap conductors must be continuous from end-to-end and contain no splices...so that's clear. However it does not specifically say that for the not over 25' tap or 10' tap.
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Given that observation, it is implicit that splices are allowed within the tap conductors for all the other rules.

Therefore, I would say that the reducing splice proposed in the OP is fine as long as the smaller size would still comply with the tap rules. I.e. if the entire run could have been the smaller size in the first place.

Cheers, Wayne
 
roger said:
Why would a tap conductor be larger than required for the equipment? IOW's, a tap is usually a smaller conductor.
I'm not saying there's not a reason, just curious.
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For one possibility, maybe the wire connectors used to make the tap have a minimum conductor size larger than both the minimum 240.21(C) compliant conductor size and the maximum conductor size the equipment's terminals take.

Cheers, Wayne
 
wwhitney said:
For one possibility, maybe the wire connectors used to make the tap have a minimum conductor size larger than both the minimum 240.21(C) compliant conductor size and the maximum conductor size the equipment's terminals take.

Cheers, Wayne
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Maybe but doubtful
 
roger said:
Why would a tap conductor be larger than required for the equipment? IOW's, a tap is usually a smaller conductor.
I'm not saying there's not a reason, just curious.
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I was going to ask this and then I realized that for example the 1/3 requirement could require conductors larger than required by the load. However in such a case it would probably be better to have a higher rated disconnect and lower rated fuses or circuit breaker.

That said, I also wonder if the larger conductors are really tap conductors.
 
jnava said:
Are you allowed to install a reducing splice at the end of a feeder tap, so it fits on the equipment disconnect terminals? It appears to me that regardless of the tap length, it is not allowed. Thoughts?
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You need to follow the definition of a "tap". Basically any smaller conductor that does not have a OCPD at its start is a tap. Generally, if you connect a smaller conductor to a larger conductor, without an OCPD, you are creating a tap.

Of course we have a problem with industry slang that calls all connections 'taps' when there are more than 3 conductors, and 'splices' when there are only two conductors.
 
jaggedben said:
I think it is allowed for 10ft taps, possibly not for 25ft and other taps. A splice to me is just an extension of tap conductors. (Where exactly does it say you can't tap a tap?)
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The last sentence of the parent text in 240.21.
...Conductors supplied under 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4.
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So my specific situation is that they are tapping a unit substation on the secondary side of a 750kVA transformer ahead of the 1200A main breaker with #600 KCMIL tap conductors. UFC code requires this to be ahead of the main. I believe the tap is under 25 feet. They are suggesting to splice the end so they can fit onto a 100A fused disconnect switch. That just doesn't seem right to me. I'm suggesting to put in a 400A switch with fuse reducers to be code compliant. I couldn't find any pin adapters online that can make that big of a transition from #600 to #1/0 max size for the 100A disconnect terminals. Same for a 200A switch with #250 KCMIL max size for terminals.
 
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