tap conductors which rules apply

[don_resqcapt19]

Hold on i am confused. In my case tap is outside and i have outside tap conductors coming into building. The total length of outside tap conductors + inside tap conductors is 12 feet. How come you all are saying i can use 25 feet rule?


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There is no location restriction on the use of the 25' tap rule. The outside tap rule does not need to be used just because part of the circuit is outside.
The only reason to use the outside tap rule is if your conductors would be over 25' and if they terminate either outside or inside, nearest the point of entry.

 

[retirede]

Hold on i am confused. In my case tap is outside and i have outside tap conductors coming into building. The total length of outside tap conductors + inside tap conductors is 12 feet. How come you all are saying i can use 25 feet rule?


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Because 12 < 25!

 

[augie47]

Hold on i am confused. In my case tap is outside and i have outside tap conductors coming into building. The total length of outside tap conductors + inside tap conductors is 12 feet. How come you all are saying i can use 25 feet rule?


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The actual wording of 240.21(B)(2) is "Taps NOT OVER 25ft Long"....which, as noted, is the situation in your case.
The vernacular is 25 ft tap rule.

 

[kwired]

Hold on i am confused. In my case tap is outside and i have outside tap conductors coming into building. The total length of outside tap conductors + inside tap conductors is 12 feet. How come you all are saying i can use 25 feet rule?


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Unlimited length is allowed on an outside tap. such tap can enter a building but must land at an overcurrent device nearest the point of entry which is basically same wording used for entry of service conductors - and for years NEC hasn't given any clear cut description of exactly what that is. Some jurisdictions are very strict on keeping the amount of entry very short, like 2, 3 maybe 5 feet of conductor max and some are rather loose with what they consider to be allowed here and may let you go as far as the 12 feet you mentioned.

 

[kwired]

There is no location restriction on the use of the 25' tap rule. The outside tap rule does not need to be used just because part of the circuit is outside.
The only reason to use the outside tap rule is if your conductors would be over 25' and if they terminate either outside or inside, nearest the point of entry.

There also is no 10 percent or one third the ampacity of the feeder overcurrent device restriction for outside feeder taps either, you could tap a 12 AWG from a 600 amp feeder if you wish but could not do this with the 10 or 25 foot tap rules.

 

[RdmanElect]

Id like to thank you for posting this thread .it has made me go on a deep dive into tap conductors and motivated me to learn more about the topic. I used to always consider (2) 200A panels off a 400A disconnect was parallel conductors even though the definition is clearly defined as "electrically joined at BOTH ends"

This is complicated stuff and we are lucky to have great minds all come together to help each other

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[Elect117]

I dont follow outside tap rule and 25 feet tap rule are two different rules.

What would apply in my case?

This thread is pretty long, and this might have already been mentioned, but you could also make the taps in a gutter above both panels inside to diffuse your concern on the outside tap rule. Then the taps would be made inside and use the 25' tap rule.

 

[hhsting]

This thread is pretty long, and this might have already been mentioned, but you could also make the taps in a gutter above both panels inside to diffuse your concern on the outside tap rule. Then the taps would be made inside and use the 25' tap rule.

I am not the designer only code enforcement reviewer.

Why I would say that when all here mention 25 ft tap rule can be made outside or inside? Their nothing in code that says do it inside 25 feet tap rule.

 

[tortuga]

I am not the designer only code enforcement reviewer.

If I were the plan reviewer I would reject the plans for two reasons first what Don and Infinity said
the conductor sizes do not meet 2017 NEC 240.21(B)(2)(2) the taps do not terminate in a single circuit breaker or a
single set of fuses that limits the load to the ampacity of the tap conductors.
They would need a 175 A OCPD for the 2/0 CU or a 3/0 CU.

And 2017 NEC 240.21(B)(2)(3)
The plans do not show the tap conductors in a raceway, it says SER cable.
I would require them to be protected from physical damage by being enclosed in an approved raceway, I would not approve any other means of protection.
They could use SER cable in the raceway, in that case the raceway and any fittings would need to be sized to the single SER cable.

 

[Jaybone812]

Is 12' greater than 10' and less than 25'?

That’s his answers right there !

 

[Carultch]

Is 12' greater than 10' and less than 25'?

This sounds like the Car Talk puzzler, where it is given in the puzzle that 90 is greater than 100, and the challenge to the listeners is to figure out the context where that is correct.

 

[kwired]

This thread is pretty long, and this might have already been mentioned, but you could also make the taps in a gutter above both panels inside to diffuse your concern on the outside tap rule. Then the taps would be made inside and use the 25' tap rule.

Could even use the 10 foot tap rule if tap length is short enough in that situation. The tap conductors still would need to have an ampacity no less than the overcurrent device they end at with any of the tap rules, so for 200 amp device you need 3/0 copper or 250 aluminum. Even though the 400 amp feeder could be allowed to be two 4/0 aluminum in parallel as long as calculated load is not over 360.