Tap Rules - Is Wire Sized to Enclosure rating or OCP rating?

[jaggedben]

I see what your saying, but what we've been saying is that that clause isn't part of the consideration here whatsoever. If a 25ft tap can land on the line terminals of a fused disconnect, then the entire disconnect is an 'overcurrent device' and a 10ft tap that lands on a fused disco meets the second clause after the 'or', regardles of anything the first part says.

I agree that your revision would reduce the confusion.

Edit: actually I don't agree with your revision, due to the following wrinkle. If I can land a 10ft tap on an MLO switchboard of appropriate rating, then I can do so whether it contains one overcurrent device or multiple overcurrent devices. But if there's only one OCPD with the possibility of adding more, I shouldn't be able to use the second clause.

 

[Tulsa Electrician]

10 foot tap rule

I had always thought that any feeder tap had to land in a OCPD. After reading 240.21(B)(1) i am reading that if all other conditions are met a 10 foot tap mat land on a MLO panel without landing in a main OCPD. Am i reading this right? :sick:

forums.mikeholt.com

 

[jaggedben]

...

The closest I can come up with to making them identical is "Not less than the rating of the single circuit breaker or single set of uses on which the tap conductors terminate." Which is a little different than the current "not less than the rating of the overcurrent protective device at the termination of the tap conductors."

I would change 'single circuit breaker or single set of fuses' to 'circuit breaker or fused disconnect' in both your proposed language above and in the 25ft tap section.

 

[don_resqcapt19]

I see what your saying, but what we've been saying is that that clause isn't part of the consideration here whatsoever. If a 25ft tap can land on the line terminals of a fused disconnect, then the entire disconnect is an 'overcurrent device' and a 10ft tap that lands on a fused disco meets the second clause after the 'or', regardles of anything the first part says.

I agree that your revision would reduce the confusion.

Edit: actually I don't agree with your revision, due to the following wrinkle. If I can land a 10ft tap on an MLO switchboard of appropriate rating, then I can do so whether it contains one overcurrent device or multiple overcurrent devices. But if there's only one OCPD with the possibility of adding more, I shouldn't be able to use the second clause.

You can do that only where the ampacity of the tap conductor is equal to or greater than the ampacity of the switchboard bus...the number of OCDPs installed or that could be installed does not matter.

 

[jaggedben]

You can do that only where the ampacity of the tap conductor is equal to or greater than the ampacity of the switchboard bus...the number of OCDPs installed or that could be installed does not matter.

Exactly. So that part is fine as written, as it could be device(s). None of that changes what comes after the 'or'.

 

[CelectricB]

Where I left off.
The drawing said with in ten feet. It did not say, comply with or use the 10' tap rule. Maybe an RFI to clarify. I see it as all must be set within ten feet. Which rule I use is up to me. Based on the picture/ drawing the 25' tap rule is applicable as it violates the 10' tap rule.
400 amp disc and 225 amp fuses.
Key word for me is conductor or length of Tap Conductor.
Key items in drawing, 400 amp fused disconnect and 225 amp fuses.
That alone pushes me over to the 25' rule.
Both ten and twenty five say "length does not exceed". If the equipment is set at the ten max feet showed in drawing the conductor would be over ten feet and moves into the 25' tap rule. Since the 25 is compliant for the drawing I would say your good.
I would also I get to choose since it is under 25' and I meet all the requirements of 1-3 of tap rule and the conductor is not over 25' long.

As far as what the OP ask yes according to the 10' rule your correct and is a violation.
Now the rest of the drawing has issues however not relevant for this discussion.

Your seen within ten feet and probably got locked in on the 10' tap rule. I see that a lot in the field.
So call and ask for clarification. Then explain to them why you ask.
If it ten foot tap rule then explain why that's an issue. See what they say other than we will get back to you.

Thank you, I found this explanation most helpful.
And thank you to everyone else who joined the conversation. I definitely was not expecting so much contention, and as a relatively new worker in this field, code continues to surprise me in that it predicates the reader understands why specific requirements are written rather than the actual content of the code.

 

[Tulsa Electrician]

Your welcome.