Taps

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Djelite

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Electrician
Does anyone know why 430.1 part refers to motor feeder taps as being no less than the feeder ampacity. While a regular feeder tap is any conductor who’s ampacity is lower than the ocpd ahead of it?
 
Djelite said:
Does anyone know why 430.1 part refers to motor feeder taps as being no less than the feeder ampacity.
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Seeing no such language in 430.1 in the 2017, 2020, or 2023 NEC. Is that a typo?

430.28 does say "Feeder tap conductors shall have an ampacity not less than that required by Part II." But that's just a reiteration of the idea that any conductor must have an ampacity at least equal to the load served. It doesn't refer to the ampacity of the feeder being tapped.

Cheers, Wayne
 
wwhitney said:
Seeing no such language in 430.1 in the 2017, 2020, or 2023 NEC. Is that a typo?

430.28 does say "Feeder tap conductors shall have an ampacity not less than that required by Part II." But that's just a reiteration of the idea that any conductor must have an ampacity at least equal to the load served. It doesn't refer to the ampacity of the feeder being tapped.

Cheers, Wayne
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Sorry that was a typo on my part it is 430.28. Under the third requirement it states the have an ampacity not less than the feeder conductor
 
It could maybe been worded better, but I think they are getting after cases where over a 25 foot tap is permitted to be used, the additional requirements for those situations are in the exception that follows.

Basically you don't have a feeder tap anymore if your conductor is same ampacity as the feeder.
 
If you like, change 430.28(3) to read "Have an ampacity not less than the feeder conductors (in which case it won't be a feeder tap)."

Cheers, Wayne
 
wwhitney said:
If you like, change 430.28(3) to read "Have an ampacity not less than the feeder conductors (in which case it won't be a feeder tap)."

Cheers, Wayne
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Of course its a feeder tap . A motor feeder tap thats the whole purpose of this thread. Why is this a tap when using requirement 3 yet a regular non motor tap is slightly different rules
 
Djelite said:
Of course its a feeder tap . A motor feeder tap thats the whole purpose of this thread. Why is this a tap when using requirement 3 yet a regular non motor tap is slightly different rules
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I look at if the wire is the same size/ type for ampacity it's an extension of the feeder it's self. So there would not be a length rule that applies to the splice (tap) location.
 
We shouldn't necessarily assume that the 240 definition of a tap applies here, so 'tap' may have the less formal meaning here. In any case, 430.28 basically just repeats some of the rules in 240.21. I don't know why it shouldn't just consist of a reference to the same.
 
I think 240.21 (10% and 30%) are based on the overcurrent device and since motors and motor overcurrent/GF devices aren't always sized the same, in 450.28 they base it on feeder conductor ampacity.
 
Elect117 said:
I think 240.21 (10% and 30%) are based on the overcurrent device and since motors and motor overcurrent/GF devices aren't always sized the same, in 450.28 they base it on feeder conductor ampacity.
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This has nothing to do with the question
 
jaggedben said:
We shouldn't necessarily assume that the 240 definition of a tap applies here, so 'tap' may have the less formal meaning here. In any case, 430.28 basically just repeats some of the rules in 240.21. I don't know why it shouldn't just consist of a reference to the same.
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This is exactly what i was getting at
 
Elect117 said:
I think 240.21 (10% and 30%) are based on the overcurrent device and since motors and motor overcurrent/GF devices aren't always sized the same, in 450.28 they base it on feeder conductor ampacity.
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That kinda makes sense but not really, unless there's a gap in my knowledge.

Is the feeder overcurrent device allowed to be larger than the feeder ampacity for motors? If not I don't exactly see what the difference is.

Also I don't really understand how Chapter 4 can modify Chapter 2 here.
 
I think I am either confused by the question or my response might not have been clear.

Lets take this one step at a time. We are installing a motor feeder tap and are sizing the motor feeder tap conductor. We are going to start with 430.28, which tells us that we first need to meet the requirements of part 2 of article 430 (Motor Circuit Conductors), and then also meet one of the following requirements in 430.28 (1) or (2) or (3). You would then use one of those to ensure the conductors are a appropriate size.

Why not use 240.21(B)? Well, that section implies the tap conductors are based on the overcurrent device protecting the feeder. Motors protection sizing is anormal to other loads because you can size the ground fault protection substantially higher.

Tap conductors are protected against ground fault by the upstream device and they terminate in their overload protection. If you terminate 3/0 in a 200A breaker, any load on that breaker will trip during a overload condition. But what about if there is a fault on the 3/0? Then the upstream feeder device need to open.

This is also why distances are taken into account. Per unit impedance on conductor can effect the ground fault current. If that 3/0 goes too far away, the fault current might get too low as seen by the upstream device and might not clear the fault.

That is my understanding of it at least.

Let me know if that helped clear things up Djelite.
 
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