Termination limitations.

Pinnie

Pinnie

Humble Disciple
Location
Ohio
Occupation
Commercial Electrician
I’m trying understand 110.14 (C).
“C) Temperature Limitations. The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device. Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both.”

So applicability wise, when sizing a conductor, you start with the ampacity specified in table 310.16. Then, if needed, derate for temperature and current carrying conductors amount. Then, if under 800 A, you can upsize your breaker to the nearest standard size per 240.4(b).

My question. Is 110.14(c) saying your final adjusted ampacity can not exceed the 60°C or 75°C ampacity in table 310.16?
 
Pinnie said:
My question. Is 110.14(c) saying your final adjusted ampacity can not exceed the 60°C or 75°C ampacity in table 310.16?
Click to expand...
It depends on the terminal temperature rating. Most are rated for 75° C so you can use that ampacity unless its limited to 60°C from other sections of the code like 334.80.
 
Pinnie said:
I’m trying understand 110.14 (C).
“C) Temperature Limitations. The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device. Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both.”

So applicability wise, when sizing a conductor, you start with the ampacity specified in table 310.16. Then, if needed, derate for temperature and current carrying conductors amount. Then, if under 800 A, you can upsize your breaker to the nearest standard size per 240.4(b).

My question. Is 110.14(c) saying your final adjusted ampacity can not exceed the 60°C or 75°C ampacity in table 310.16?
Click to expand...
You cannot just upsize the OCPD. Please read 240.4(B). There are restrictions.
 
infinity said:
It depends on the terminal temperature rating. Most are rated for 75° C so you can use that ampacity unless its limited to 60°C from other sections of the code like 334.80.
Click to expand...
But is that what it means when it says “not to exceed the lowest temperature rating of any connected termination, conductor or device”?

If so that seems worded confusingly.
 
Pinnie said:
But is that what it means when it says “not to exceed the lowest temperature rating of any connected termination, conductor or device”?

If so that seems worded confusingly.
Click to expand...
Yes. If they're all 75°C then you can use the 75° C ampacity unless limited to 60° C by another code section.
 
infinity said:
Yes. If they're all 75°C then you can use the 75° C ampacity unless limited to 60° C by another code section.
Click to expand...
Okay and just to clarify what it does NOT mean, is you have to start your derating calculations from that point (like grok just tried to convince me for 20 minutes.)
 
Pinnie said:
Okay and just to clarify what it does NOT mean, is you have to start your derating calculations from that point (like grok just tried to convince me for 20 minutes.)
Click to expand...
No, ampacity adjustments can be from the maximum ampacity of the conductor for example THHN can be derated from its 90°C ampacity.
 
The ampacity _at the terminals_ is set by the temperature rating of the terminals. Since the terminals usually have a lower temperature rating than the conductor insulation, then the terminal temperature rating governs. If by some bizarro situation you have elevated temperatures at the terminals, then you would do ampacity adjustments at the terminal location from the _terminal_ temperature rating.

The ampacity _in the conduit_ is set by the temperature rating of the conductor insulation. Adjustments for number of current carrying conductors or ambient conditions are from the conductor temperature rating.

Another bizarro situation is if the conductor temperature rating is lower than the terminal temperature rating, in which case the lower conductor temperature would govern.

After you calculate the ampacity at the different locations of the conductor, you take the lowest value as the ampacity of the conductor.

In normal situations, the ampacity at the terminals will likely be the 75C ampacity (with no adjustments), and the ampacity in the conduit will be derated/adjusted from the 90C ampacity.
 
winnie said:
If by some bizarro situation you have elevated temperatures at the terminals, then you would do ampacity adjustments at the terminal location from the _terminal_ temperature rating.
Click to expand...
How do you do anmpacity adjustments at the terminal location from the terminal temperature rating?
 
winnie said:
If by some bizarro situation you have elevated temperatures at the terminals, then you would do ampacity adjustments at the terminal location from the _terminal_ temperature rating.
Click to expand...
While that would be logical, I don't believe that's correct. Instead, my understanding is that it is up to the manufacturer of the equipment to indicate the allowable ambient temperature in which the equipment may be used, and to plan accordingly. The temperature termination rating is just a short hand for what column to use in Table 310.16 when sizing your conductors at the terminal.

winnie said:
Another bizarro situation is if the conductor temperature rating is lower than the terminal temperature rating, in which case the lower conductor temperature would govern.
Click to expand...
If the terminal temperature rating is 75C only, you may not use 60C rated conductor insulation. If the terminal temperature rating is 60C/75C, you can either (a) use 60C rated conductor insulation and the termination ampacity would be from the 60C column or (b) use 75C or higher rated conductor insulation, and the termination ampacity would be from the 75C column.
 
wwhitney said:
While that would be logical, I don't believe that's correct. Instead, my understanding is that it is up to the manufacturer of the equipment to indicate the allowable ambient temperature in which the equipment may be used, and to plan accordingly. The temperature termination rating is just a short hand for what column to use in Table 310.16 when sizing your conductors at the terminal.
Click to expand...
I would think they would size the terminal ampacity based off the max conductor size allowed on it yeah?
wwhitney said:
If the terminal temperature rating is 75C only, you may not use 60C rated conductor insulation.
Click to expand...
Why not? If you limit amperage to the 60C column of the conductor then it would be fine.
 
Pinnie said:
I would think they would size the terminal ampacity based off the max conductor size allowed on it yeah?
Click to expand...
Lug conductor size is based on what manufacturers want it to be.
Terminal ampacity is based on the temperature rise allowed for the complete assembly.
The maximum allowable terminal conductor size depends on the wire bending space.
 
infinity said:
The terminal would need to rated for 60°/75° C to use a 60° C conductor not 75° C only.
Click to expand...
So you can use a higher temperature rated conductor but not terminal? Is this because 110.14 allows higher rated conductors to be used but never says higher rated terminals can be used?
 
jim dungar said:
Lug conductor size is based on what manufacturers want it to be.
Click to expand...
Makes sense. All we need to know is what they are rated for they can figure out how over/under built they want to make them for their own liabilities sake
jim dungar said:
Terminal ampacity is based on the temperature rise allowed for the complete assembly.
Click to expand...
this aligns with my conceptualization
jim dungar said:
The maximum allowable terminal conductor size depends on the wire bending space.
Click to expand...
This is news to me and very interesting. There is no min bending radius on single conductors as far I know. I know there are for cable assemblies. But it makes sense that the wire need to GET to the terminal. I would assume it’s also based on how large of a conductor can actually mechanically terminate on a lug/terminal (assuming they are covered on amperage).
 
Pinnie said:
There is no min bending radius on single conductors as far I know. I know there are for cable assemblies.
Click to expand...
Correct.
The NEC wire bending space is for being able to get conductors into the lugs. It is measured between the lugs and the enclosure walls.
 
infinity said:
The terminal would need to rated for 60°/75° C to use a 60° C conductor not 75° C only.
Click to expand...
Can you cite an example of this? Square D for example lists their breakers for use with 75 degree terminations. If what you say is true, then I assume we wouldn't be able to terminate Romex to a Square D breaker since we are limited to using the 60 degree table for it. I have never seen a terminal that is rated for 60/75 degrees
 
You must log in or register to reply here.
Top