- Location
- Illinois
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- retired electrician
I know what it says and it does not say what it was intended to say. Those are two totally different clauses with totally different meanings signified by the use of the "or" between the clauses.
Tap Rules - Is Wire Sized to Enclosure rating or OCP rating?
- Thread starter CelectricB
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wwhitney
Senior Member
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- Berkeley, CA
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- Retired
OK, I agree that the two breakers don't protect the busbar from SCGF. So that may not work for (2020) 408.36 Exception #1. The only thing keeping me from fully agreeing is that then I have no idea what 408.36 Exception #1 means or is meant to allow.
Maybe the exception is meant for panelboards where the factory main breaker is actually two ganged double/triple pole breakers?
Cheers, Wayne
wwhitney
Senior Member
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- Berkeley, CA
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- Retired
Right, for compliance with 240.21(B)(1)(1)(b), we have two choices, and can pick either one.
So what is the difference between the second option referring to "the rating of the overcurrent protective device at the termination of the tap conductors" and 240.21(B)(2)(2) referring to "the rating of the single circuit breaker or single set of fuses on which the tap conductors terminate"?
To mean, those mean the same thing. I.e. 240.21(B)(1)(1)(b) is giving you all the options present in 240.21(B)(2)(2), plus whatever options the first clause in 240.21(B)(1)(1)(b) is meant to also offer.
Cheers, Wayne
- Location
- Illinois
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- retired electrician
If they the same meaning, when why the different language from the same CMP? There was a reason why they selected differing language and it is my opinion they did so because the requirements are actually different. Until the language is changed I will continued to see the 10' tap rule as requiring the tap conductor ampacity to be equal to the rating of the fusible disconnect and not the fuses installed in it.
Tulsa Electrician
Senior Member
- Location
- Tulsa
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- Electrician
I agree with that and is how I read it as well.
Now if I was the op. I would look at it this way.
His drawing said:
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Tulsa Electrician
Senior Member
- Location
- Tulsa
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- Electrician
For some reason the rest my post was chopped off.
Have to redo.
Edit: must be a spam filter.
Have to redo.
Edit: must be a spam filter.
Tulsa Electrician
Senior Member
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- Tulsa
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- Electrician
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.
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.
wwhitney
Senior Member
- Location
- Berkeley, CA
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- Retired
Going back to the OP, my understanding is that when a fusible disconnect is called "400A," that means it physically accepts fuses of size 225A to 400A. Once you put 225A fuses in it, isn't "the rating of the equipment" now 225A? Since the equipment includes the fuses.
Cheers, Wayne
Cheers, Wayne
- Location
- New Jersey
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- Journeyman Electrician
That's answers the OP's question. Most of this other stuff is unrelated and confusing.
jaggedben
Senior Member
- Location
- Northern California
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- Solar and Energy Storage Installer
I don't see any meaningful difference.
One says: "the ampacity of the tap conductors is ... not less than the rating of the overcurrent device at the termination of the tap conductors"
The other says "the tap conductors terminate in a single circuit breaker or set of fuses that limit the load to the ampacity of the tap conductors"
Are you seriously suggesting that the former prohibits landing on the normal line terminals of a fused switch, and the latter doesn't?
There's also the oddity of arguing that a 9ft tap that complies with the 25ft tap rule must also comply with the 10ft tap rule.
- Location
- Illinois
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- retired electrician
yes
jaggedben
Senior Member
- Location
- Northern California
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- Solar and Energy Storage Installer
I don't know, but if someone decides to write 2+2=4 in one place and 4=2+2 in another, it does not follow that the meaning is different because they rearranged the symbols.
jaggedben
Senior Member
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- Northern California
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- Solar and Energy Storage Installer
Wow. We will never agree on this.
- Location
- Illinois
- Occupation
- retired electrician
For sure we will not The code language does not match the intent of the rule, but the code language is very clear.
- Location
- Illinois
- Occupation
- retired electrician
It is way more than rearranging...totally different words between the 10' and the 25' tap rules.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
OK, so I can get my PI right, how would you rewrite the second half of 240.21(B)(1)(1)(b) to mean the same thing as 240.21(B)(2)(2)?
We can't literally copy and paste, as 240.21(B)(1)(1) starts off "The ampacity of the tap conductors is as follows:" So the second half of (b) should have "the ampacity of the tap conductors" as the subject. While 240.221(B)(2)(2) has "the tap conductors" as its subject. So we'll need to change the sentence form at least somewhat to deal with the different subject choice.
[Which, BTW, is for me sufficient explanation of why they aren't currently identical.]
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."
Cheers, Wayne
jaggedben
Senior Member
- Location
- Northern California
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- Solar and Energy Storage Installer
You're going to have to spell out what exactly you think has different meaning.
- Location
- Wisconsin
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- PE (Retired) - Power Systems
Explain again why a fusible switch is not an overcurrent device?
What about when window style CTs are used with over current relays?
Conductors cannot terminate directly to The majority of fuses, applied per the NEC, they can only connect to some type of fuse holder or mounting base.
What about when window style CTs are used with over current relays?
Conductors cannot terminate directly to The majority of fuses, applied per the NEC, they can only connect to some type of fuse holder or mounting base.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I agree. IMO it's hogwash to say the line terminals of a fused safety switch do not count as conductors landing directly on an ocpd.
- Location
- Illinois
- Occupation
- retired electrician
The language says the rating of the "equipment" and with a fusible disconnect the equipment rating is the disconnect. I believe that part of the rule was intended to apply only where the equipment contains more than one overcurrent device. By the use of the (s) it clearly permits the equipment to contain more than one OCPD. The permission to have more than one OCPD protect the 10' tap conductor is one of the differences between the 10' and 25' tap rules. The (s) is what telling me that the tap conductor feeding a single fused disconnect must have an ampacity equal to the rating of the disconnect. If "device(s)" would be replaced with "devices" the problem goes away.
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