tap conductors which rules apply

The 2/0 copper for a 200 amp feeder just doesn't apply at all here as these are not supplying the entire load of the dwelling.

But what others are saying is the feeder taps must have an ampacity of 200 amps (no next size up OCPD allowed for the feeder tap situation here)

Kind of makes no sense because if these were service conductors instead of feeder taps they could be 4/0 aluminum as long as load calculation were not over 180 amps. But that is how the feeder tap rules are written.
 
Likewise, if the conductors were 8 long instead of 12, you could use the 10' rule, the 25' rule, or the outside rule if you can meet all the requirements. As others mentioned, the conductors may not be nearest point of entry, so that option is out. Between the 10' and 25' rules, if you meet the conditions for both it doesn't really matter which rule you're using. You only need to comply with one to have a legal tap. If you want to skimp on something to force use of the 10' rule and not meet the 25' rule, you could if the conductors we're 10' long or less.
 
Yes. Outside versus inside isnt relevant for the 10 and 25 ft rules. To use the outside rule, the entire tap must be outside or terminate in a structure nearest point of entry.
 
hhsting said:
I have townhome residential that has 400A fused disconnect with 400A fuses outside on the front wall of the townhouse and tap conductors are being brought in Panels A and Panels B. They are about 12 feet in length.

My question is that should 25 feet tap rule apply here or outside tap rule apply here?
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2023 NEC TX
Section 240.21(B)(2) Taps Not Over 25 ft Long. What size are your feeder conductors? Should be not less than .33 of the 400 amp OCPD.

The conductors are limited to 25 feet of conductors and not any more, including from terminal -to-terminal and make up on each end.

Do you have an EGC for each run? If so, use T. 250.122.

What size of fuses in the 200 amp disconnects, 240.21 (2) Can't exceed the tap conductors ampacity limit.

Does your jurisdiction require SPD's for feeders? Section 215.18 (A)(1)(4).

Section 242.14(B) Feeder Supplied Building or Structure

Thanks for reading
Comments accepted
TX+MASTER#4544
 
suemarkp said:
Likewise, if the conductors were 8 long instead of 12, you could use the 10' rule, the 25' rule, or the outside rule if you can meet all the requirements. As others mentioned, the conductors may not be nearest point of entry, so that option is out. Between the 10' and 25' rules, if you meet the conditions for both it doesn't really matter which rule you're using. You only need to comply with one to have a legal tap. If you want to skimp on something to force use of the 10' rule and not meet the 25' rule, you could if the conductors we're 10' long or less.
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The only thing the 10' rule gives is the permission to use a smaller conductor, but in this case the tap conductor minimum size is based on the load end 200 amp OCPD.
 
infinity said:
They're not parallel conductors because they are not connected together on both ends. Yes they meet the definition of tap conductors.
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Gotcha, so if I were to do a 400A service and have (2) 200A panels off the 400A disconnect, I'm limited to 25feet ?

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RdmanElect said:
Gotcha, so if I were to do a 400A service and have (2) 200A panels off the 400A disconnect, I'm limited to 25feet ?
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If the tap conductors are inside of the building then yes. If they're outside and can meet all of the rules for the outside tap rule then they can be unlimited in length.
 
RdmanElect said:
Is this a tap conductor or parallel conductors? I dont see where tap conductors come into play here.

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But one could run say parallel 4/0 aluminum to near the panelboards and then use the 10 foot tap rule to each panel, however I believe you still need tap conductors rated no less than the overcurrent device being supplied so they would still need to be 250 aluminum or 3/0 copper for the taps.
 
kwired said:
But one could run say parallel 4/0 aluminum to near the panelboards and then use the 10 foot tap rule to each panel, however I believe you still need tap conductors rated no less than the overcurrent device being supplied so they would still need to be 250 aluminum or 3/0 copper for the taps.
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That raises the question of why the tap rules are written in a way that is incompatible with 240.4(B) in the first place.

I understand 240.4(B) as based on the idea that "the OCPD provides the SC/GF protection, and the load calculation provides the overload protection." In 240.21(B), we encounter a similar situation, where the OCPD at the supply end of the tap conductor provides the SC/GF protection, and the OCPD at the load end of the tap conductor provides the overload protection. But a load calculation would provide overload protection equally well as in 240.4(B).

So why does the higher nominal rating of the SC/GF protection that a tap conductor has mean that we need to be stricter about the overload protection? I.e. what risky scenario does 240.4(B) permit on the basis of it being sufficiently unlikely that would become worse if the SC/GF protection at the supply end of the conductor is provided by an OCPD with a nominal rating in excess of the conductor ampacity?

Cheers, Wayne
 
infinity said:
If the tap conductors are inside of the building then yes. If they're outside and can meet all of the rules for the outside tap rule then they can be unlimited in length.
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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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hhsting said:
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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You either have the misapprehension that (a) when the tap originates outside you must use the outdoor tap rule or (b) the 25' tap rule cares whether the conductors are inside or outside, or maybe both.

Neither of those is true. The installation satisfies the requirements of the 25' trap rule. As the OCPD supplied is not nearest the point of entrance of the tap conductors, the installation does not satisfy the requirements of the outdoor tap rule.

hhsting said:
Anyone?
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You have already been told, or shown enough to conclude with only minimal logic, that the 25' tap rule applies. About 5 times.

Cheers, Wayne
 
wwhitney said:
You either have the misapprehension that (a) when the tap originates outside you must use the outdoor tap rule or (b) the 25' tap rule cares whether the conductors are inside or outside, or maybe both.

Neither of those is true. The installation satisfies the requirements of the 25' trap rule. As the OCPD supplied is not nearest the point of entrance of the tap conductors, the installation does not satisfy the requirements of the outdoor tap rule.


You have already been told, or shown enough to conclude with only minimal logic, that the 25' tap rule applies. About 5 times.

Cheers, Wayne
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Yes but others questioning and then their response mixing me up

Thanks for clarification


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Regardless of tap rule does 225.31 not require a disconnect nearest the point of entrance? Could be the 400A switch outside but it still should be nearest the point of entrance.
 
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