# Using the 90C column of the ampacity table - 110.14(C)(2)



## Carultch (May 14, 2013)

NEC110.14(C)(2) allows one potential use of the 90C column of the NEC ampacity table, when you have field-installed 90C connectors at both ends. Maybe they are lugs on a busbar, splices, insulation piercers, or something similar.

I'd like to refer to this video:
https://www.youtube.com/watch?v=k7d03Tic6LE#t=870

See time mark 10:40 when he introduces this particular concept, and see time mark 14:30 when he gives a specific example I'd like to discuss.

The example is a case where you screw up, and forget the 75C termination rule. So you leave most of your otherwise incorrect 90C sized wire in place, and connect a local section of proper 75C sized wire at each end.

My question:
Is there a reason he shows dedicated enclosures for these connectors?
Is that required, or is that simply a one method of doing this?

Would it be acceptable to have the 90C connectors in the equipment gutter space, and still take credit for the 90C ampacity?

I don't see dissassembling the conduit and adding splice boxes, as an easy contingency solution. If I screwed up, I'd much rather put my Polaris insultaps inside the equipment, and leave the raceway alone.


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## Dennis Alwon (May 9, 2009)

I did not look at the vid but you do not have to use 75C wire just because the termination is 75C. You cannot use the 90C column except for de-rating un;less all terminations and conductors etc are rated 90C. You probably won't find that anywhere. 

So use 90C but the final ampacity must be sized by the weakest link. If the terminals are 60C then you must use 60C column


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## Carultch (May 14, 2013)

Dennis Alwon said:


> I did not look at the vid but you do not have to use 75C wire just because the termination is 75C. You cannot use the 90C column except for de-rating un;less all terminations and conductors etc are rated 90C. You probably won't find that anywhere.
> 
> So use 90C but the final ampacity must be sized by the weakest link. If the terminals are 60C then you must use 60C column


I've attached a snapshot of the video. My question is specific to this example.

I understand the concept of how to start properly, with the 75C or 60C columns as requried. The example is how to salvage a situation where someone didn't start properly.


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## Dennis Alwon (May 9, 2009)

I think what mike holt is saying is that you can save wire costs by adding a jb and use a smaller wire rated at 90C between the junction boxes since there are no terminals other than a splitbolt or so. So if you had a long run you could come out of a panel with a larger 75C wire and go to a jb. From there go to a smaller 90C col. wire from one jb to the other jb and then use the larger 75C column for the short piece again.


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## Dennis Alwon (May 9, 2009)

What do you mean by not starting properly?


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## Carultch (May 14, 2013)

Dennis Alwon said:


> What do you mean by not starting properly?


Suppose we have a 400A panel, and a 400A disconnect, and I installed 500 kcmil Cu between them, thinking I could take credit for the 90C column.

Then I realize I screwed up, and need 600 kcmil to meet the terminations.

Do I need separate enclosures for the 90C splices, that I'll use in order to fix the situation?


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## Dennis Alwon (May 9, 2009)

IMO, you can splice inside the enclosure if you have the space. No need for another box. I think mike holt did that just to show it more clearly


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## Carultch (May 14, 2013)

Dennis Alwon said:


> IMO, you can splice inside the enclosure if you have the space. No need for another box. I think mike holt did that just to show it more clearly


Ok, that makes sense. Thank's for discussing this with me.


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## chicken steve (Mar 22, 2011)

MH delves into_ equipment/lug/termination_ values , insisting the 90C _equipment_ rare , with an _ex._ of wires used as a splice between two 90C bus bars.

He then up's the ante' by showing us the same 90C method between two JB's , the JB displacing any 90C heat from 75C equipment.

So can this be done, supposedly where a lesser feeder (as shown) is run @ 90C , and then 75C from JB(s) to equipment is your Q Carultch? 

My own opinion is anything that encloses /terminates the 90C conductors would need to be 90C themselves.

~CS~


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## Carultch (May 14, 2013)

chicken steve said:


> My own opinion is anything that encloses /terminates the 90C conductors would need to be 90C themselves.


That's what I thought the reason for the extra splice boxes would be. My question is to figure out if this is a requirement.

Obviously I wouldn't want to take apart a conduit assembly if I didn't need to.


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## chicken steve (Mar 22, 2011)

MH is really off on a long winded dissertation , that makes him hard to follow Carultch. But i think the jist is the listed running temps of all components being similar.

the conductor can be rated for 90C, the terminal it lands on can be 90C, but the point _(i believe) _he's trying to hammer home is the equipment itself needs to be 90C , otherwise anything 90C can't exist within it.

~CS~


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## Dennis Alwon (May 9, 2009)

chicken steve said:


> My own opinion is anything that encloses /terminates the 90C conductors would need to be 90C themselves.
> 
> ~CS~


And where did you get this opinion from? There is nothing in the NEC that I know about that supports this thinking.


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## chicken steve (Mar 22, 2011)

I'll say it's my opinion based on MH's opinion Denny. 

A 110.3B , albeit a strained one....

That said, why didn't he take it a step further, and insist the 90C conductor were to land on a 90C OCPD , inside a 75C enclosure?


~CS~


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## don_resqcapt19 (Jul 18, 2010)

The use of the separate enclosures for the splices is likely based on the length of 75° wife needed. The code does not directly address this issue, but the length is often specified as 4'. This is based on the fact that the UL standard for breakers requires that the testing be performed with 4' of 75°C conductors connected to the breaker.


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## Dennis Alwon (May 9, 2009)

don_resqcapt19 said:


> The use of the separate enclosures for the splices is likely based on the length of 75° wife needed. The code does not directly address this issue, but the length is often specified as 4'. This is based on the fact that the UL standard for breakers requires that the testing be performed with 4' of 75°C conductors connected to the breaker.


So is the reason for the 4' for the dissipation of heat?


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## chicken steve (Mar 22, 2011)

That's interesting, but i'm not sure where to go with it....:001_huh: because it implies 90C installs have to be a certain distance from 75C installs, which would follow suit with 60C installs

~C:blink:S~


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## don_resqcapt19 (Jul 18, 2010)

Dennis Alwon said:


> So is the reason for the 4' for the dissipation of heat?


It would serve that purpose where you have added the 75°C conductors to the 90°C ones. I have no idea how much would really be needed for that purpose. I just know that they use 4' of conductor when testing the breakers.


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## Carultch (May 14, 2013)

don_resqcapt19 said:


> It would serve that purpose where you have added the 75°C conductors to the 90°C ones. I have no idea how much would really be needed for that purpose. I just know that they use 4' of conductor when testing the breakers.


It sounds like the message is clear. Do it right the first time. Select the correct wire, per the 75C column of the ampacity table.

Yeah, sure, the nifty work-around does exist for someone who screwed up, but meeting it in a way that is objectively acceptable is very complicated and impractical.

This is actually relevant to a situation I'm working with right now. My 50A equipment only has terminals capable of accepting #8 wire, and thus the panelboard on the other end of the wire must have 75C rated terminations. I've informed the manufacturer that this is problematic, and that they should always size terminals to at least accept the next larger size wire than the absolute minimum. If I were to connect this equipment to an old breaker that has 60C terminations, I'd need to find an appropriate place for a 75C rated splice to transition to #6 as required.


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## tates1882 (Sep 3, 2010)

Carultch said:


> It sounds like the message is clear. Do it right the first time. Select the correct wire, per the 75C column of the ampacity table.
> 
> Yeah, sure, the nifty work-around does exist for someone who screwed up, but meeting it in a way that is objectively acceptable is very complicated and impractical.
> 
> This is actually relevant to a situation I'm working with right now. My 50A equipment only has terminals capable of accepting #8 wire, and thus the panelboard on the other end of the wire must have 75C rated terminations. I've informed the manufacturer that this is problematic, and that they should always size terminals to at least accept the next larger size wire than the absolute minimum. If I were to connect this equipment to an old breaker that has 60C terminations, I'd need to find an appropriate place for a 75C rated splice to transition to #6 as required.


Reducing crimp connectors. I use these on center pivots where disconnect to machine exceeds 1/4mile and wire size is increased for VD. A lot of times its a 60amp pivot with 2/0 or larger feeding it, most 60 amp discos lugs are #2 or smaller hence using a crimp pin .


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## chicken steve (Mar 22, 2011)

Ok, so upsizing a conductor for VD moving it down to the 75C collum via the next largest _(or whatever it's calc'd out to be) _ dissipates the heat landing it on terminations , and/or entering equipment. Methinks i get that.

For the sake of debating MH's point_ (or my perception of it)_ , can i run 90C conductors _through_ 75C equipment ? 

~CS~


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## Dennis Alwon (May 9, 2009)

chicken steve said:


> For the sake of debating MH's point_ (or my perception of it)_ , can i run 90C conductors _through_ 75C equipment ?
> 
> ~CS~


Yes, Remember the ampacity of 90C wire cannot be more than the 75C rating of the terminals so the conductor will only carry current equal to 75C.


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## don_resqcapt19 (Jul 18, 2010)

Carultch said:


> ...
> Yeah, sure, the nifty work-around does exist for someone who screwed up, but meeting it in a way that is objectively acceptable is very complicated and impractical. ...


It may not be a screw up...it may be a value engineering issue


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## Carultch (May 14, 2013)

don_resqcapt19 said:


> It may not be a screw up...it may be a value engineering issue


That may be the case. I've yet to come across an example where it works.

My initial thought is that if conductors are long enough to justify the cost of a complicated raceway & junction box construction, as well as the sweatheart connectors, and the extra labor, then the conductors are probably long enough for voltage drop to matter.


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## cabletie (Feb 12, 2011)

Here is a buliten from Square D that explains it pretty well

http://static.schneider-electric.us/docs/Power Management/0110DB9901.pdf

The next topic could be is a breaker ever rated at 100% of its rating? I think that also goes along with the breaker being in an enclosure and not being able to dissipate heat.


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## chicken steve (Mar 22, 2011)

thx cabletie....


about 1/2 way down....



> For electrical equipment rated for 600 V and less, terminations are typically rated at 60 °C, 75 °C or 60/75 °C.* No distribution or utilization equipment is listed and identified for the use of 90 °C wire at its 90 °C ampacity. *
> Thisincludes distribution equipment, wiring devices, transformers, motor control
> devices, and even utilization equipment such as HVAC, motors, and light
> fixtures.



~CS~


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## Carultch (May 14, 2013)

cabletie said:


> The next topic could be is a breaker ever rated at 100% of its rating? I think that also goes along with the breaker being in an enclosure and not being able to dissipate heat.


Ask, and you shall receive:
http://static.schneider-electric.us...nsulated Case Circuit Breakers/0600DB0101.pdf

Interestingly enough, they talk about how the entire equipment needs to be rated for the application. And not just a plug and play OCPD component of the equipment.



> In enclosures that are supplied with standard-rated circuit breakers, it is not necessarily possible to replace a standard-rated circuit breaker with a 100%-rated circuit breaker and obtain a 100% rating. The enclosure must meet the minimum enclosure and ventilation requirements of the circuit breaker and be marked as such.


I seldom ever deal with any overcurrent device that is 100% rated, but I do deal with continuous loads all the time. My understanding that equipment is only standard rated, until proven continuous duty rated.

The industry norm I've noticed is that equipment without OCPD usually is continuous duty rated (unfused safety switches, rotary switches, contactors), while equipment with OCPD usually is standard rated.

What are some advantages of using continuous duty breakers?
(Of course, if you can find them)


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## melrub480v (Apr 25, 2021)

Carultch said:


> I've attached a snapshot of the video. My question is specific to this example.
> 
> I understand the concept of how to start properly, with the 75C or 60C columns as requried. The example is how to salvage a situation where someone didn't start properly.


Yes I've always thought you could use 90c splicing devices in between the 2 points before you terminate then at those same 2 points you go back to 75c wire so it might have to be up sized a bit.


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## kb1jb1 (Nov 11, 2017)

melrub480v said:


> Yes I've always thought you could use 90c splicing devices in between the 2 points before you terminate then at those same 2 points you go back to 75c wire so it might have to be up sized a bit.


Very old thread but good to bring up again because many electricians still do not know how to use the tables. Mike Holt holds an opinion and goes off into situations that most will never run into. If you are doing a 400 amp feeder you should know how to plan for it. Cutting and installing pull or junction boxes can be quite expensive. 

I always get caught on the dates things were posted.


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## melrub480v (Apr 25, 2021)

kb1jb1 said:


> Very old thread but good to bring up again because many electricians still do not know how to use the tables. Mike Holt holds an opinion and goes off into situations that most will never run into. If you are doing a 400 amp feeder you should know how to plan for it. Cutting and installing pull or junction boxes can be quite expensive.
> 
> I always get caught on the dates things were posted.


Yes actually I agree with you wholeheartedly. Me personally I just like to keep it in the back of my head in case I ever need to get out of a jam. But it can get expensive, I've run into electricians that will actually do this and think it's cheaper, I guess in some instances it could be. But pull boxes and splicing devices like Polaris lugs etc. Are very expensive. Let alone the man hours it takes to do the work.


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## Dennis Alwon (May 9, 2009)

In many cases you can splice within the panelboard. This is especially helpful if you have a very long run with expensive wire


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## paulengr (Oct 8, 2017)

I don’t get all the extra complication.

If the wiring space was overloaded such as say exceeding 3 current carrying conductors then sure, you derate. Granted in large panels this does not apply but that’s where 508A does.

With a lug though the issue is nearly always the insulating material (plastic and rubber) physically in contact with it that is only rated for 75 C. There may be other cases but I haven’t seen one yet.

So I “get” the 75 C rating. So often we have 90 C rated wiring between enclosures but 75 C ratings at the lugs. The cable itself isn’t the issue. There is for instance no reason not to use the 90 C rating inside a conduit with say 9 conductors derated and taking the lesser value. You wouldn’t derate the conduit starting at 75 C…that’s silly.

There are for instance crimp on sleeves on the market that reduce say a 500 MCM cable to 350 MCM to land it. This would be useful for say voltage drop reasons or “oops…we forgot about the 4/C per phase 1200 A breaker only accepts 350 MCM”. Other than for reasons that it may not exist no reason not for a size increasing sleeve. I could do the same thing with crimped bolted lugs and a short piece of cable meeting the 75 C sizing. So why all the extra enclosure time wasting? This stuff is done all the time. As long as we don’t cause constriction resistance it’s not going to cause excess heat and the lugs solve that.


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