Wire insulation temperature VS. Termination temperature (Again)

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rbalex said:
Yes, so?
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You asked if I read the Whitebook. Well, no... not the entire book. ;)

But I did read the section of AALZ that you noted. My earlier post provided a comment, an excerpt, and a link to the online publication of AALZ.
 
Smart $ said:
You asked if I read the Whitebook. Well, no... not the entire book. ;)

But I did read the section of AALZ that you noted. My earlier post provided a comment, an excerpt, and a link to the online publication of AALZ.
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And it doesn't support you.
 
rbalex said:
And it doesn't support you.
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I agree it is not concise enough to beleaguer the point.

I'd rather focus the debate on the equipment being rated 75°C. Consider a heavily loaded 75°C-rated panelboard with 75°C-rated wiring on all but one circuit, which is uses 60°C wire in agreement with charlie b's assessment. No terminations are marked or rated 60° or 60/75°C . What if the measured internal operating temperature exceeds 60°C? Is there a violation, and if so, what is it?
 
Smart $ said:
I do not agree.

My understanding is that it is not only a matter of the wire not exceeding the 60°C temperature based on the current it will handle, but that the equipment is rated 75°C and permitted to reach that temperature under normal operation. When it does, the insulation temperature of the wire will have been exceeded. There is no accepted method to "derate" 75°C-rated equipment for use with 60°C-rated conductors.
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How would a 60 degree conductor limited to the 60 degree ampacity exceed the insulation temperature of the wire?
 
david luchini said:
How would a 60 degree conductor limited to the 60 degree ampacity exceed the insulation temperature of the wire?
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If the utilization equipment generated enough heat itself during normal use to raise the terminals marked 75C to 75C. Just like some luminaires require the use of 90C insulation on the conductors connected to them.

Cheers, Wayne
 
It seems to me that the AALZ language in both the "Appliance and Utilization Equipment Terminations" and for "Distribution and Control Equipment Terminations" sections supports the Square D white paper interpretation. Namely:

Under "Appliance and Utilization Equipment Terminations" is the sentence "If the termination provisions on equipment are based on the use of other conductors, the equipment is either marked with both the size and temperature rating of the conductors to be used or with only the temperature rating of the conductors to be used." The "to be used" language reads as mandatory. So if the terminals are marked "75C" that would mean that 75C or greater insulation is required.

Likewise, "Distribution and Control Equipment Terminations" says "Some distribution and control equipment is marked to indicate the required temperature rating of each field-installed conductor." Again the word "required" is mandatory language.

Cheers, Wayne
 
Carultch said:
That's what I originally stated. That a 75C equipment terminal rating is not backwards-compatible by default with 60C wire, unless dual rated 60C/75C.
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You guys have me confused, so speak loudly and slowly. :D

Say you have a load with 75 degree terminals that requires conductors rated at 50A. Leaving out derating for the sake of simplicity, you'd need a #8 THWN (75 degree rated) to service the load and keep the terminals below 75 degrees. If you were to substitute, say TW wire (60 degree rated), you'd have to go to a #6 to keep the conductors under 60 degrees. 60 degrees is less than 75 degrees, so why would this be a problem for the terminals?
 
ggunn said:
You guys have me confused, so speak loudly and slowly. :D

Say you have a load with 75 degree terminals that requires conductors rated at 50A. Leaving out derating for the sake of simplicity, you'd need a #8 THWN (75 degree rated) to service the load and keep the terminals below 75 degrees. If you were to substitute, say TW wire (60 degree rated), you'd have to go to a #6 to keep the conductors under 60 degrees. 60 degrees is less than 75 degrees, so why would this be a problem for the terminals?
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The 60°C wire is terminated in 75°C-rated equipment that may operate at 61-75°C.

When discussing terminal temperature ratings, it seems many believe the current running through the conductor is the only source of generated heat. However, in enclosures where wire and terminals are not the only equipment, the other equipment can also be the source of heat.
 
ggunn said:
You guys have me confused, so speak loudly and slowly. :D

Say you have a load with 75 degree terminals that requires conductors rated at 50A. Leaving out derating for the sake of simplicity, you'd need a #8 THWN (75 degree rated) to service the load and keep the terminals below 75 degrees. If you were to substitute, say TW wire (60 degree rated), you'd have to go to a #6 to keep the conductors under 60 degrees. 60 degrees is less than 75 degrees, so why would this be a problem for the terminals?
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:thumbsup:
 
This is the actual NEC rule as self-summarized:

110.14(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.
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As I mentioned earlier, it is important to read it in context of the definition of ampacity:

Ampacity. The maximum current, in amperes, that a conductor
can carry continuously under the conditions of use
without exceeding its temperature rating.
(underline mine)
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It does NOT require all components have the same temperature rating OR marked with a temperature rating for use with a lower rated component, rather it simply requires that a given component's temperature rating cannot be exceeded under it's "condition of use".

All other Subsection of 110.14(C) should be read and interpreted in this context.
 
Smart $ said:
The 60°C wire is terminated in 75°C-rated equipment that may operate at 61-75°C.

When discussing terminal temperature ratings, it seems many believe the current running through the conductor is the only source of generated heat. However, in enclosures where wire and terminals are not the only equipment, the other equipment can also be the source of heat.
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This is a legitimate point and UL addresses it under other specific Category codes (QEUY for panelboards for example). HOWEVER it refers back to AALZ as most Category Codes ultimately do. It still says nothing about marking the terminals.

From Category Code QEUY:

Unless the panelboard is marked to indicate otherwise, the termination
provisions are based on the use of 60°C ampacities for wire sizes 14–1
AWG, and 75°C ampacities for wire sizes 1/0 AWG and larger as specified
in Table 310.15(B)(16) of ANSI/NFPA 70, ‘‘National Electrical Code’’
(NEC). However, 3-wire, single-phase service entrance or feeder conductors
for dwelling units may be as covered in Section 310.15(B)(7) of the
NEC. Termination provisions are determined based on values provided in
Table 310.15(B)(16) or Section 310.15(B)(7), with no adjustment made for
correction factors.
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rbalex said:
This is a legitimate point and UL addresses it under other specific Category codes (QEUY for panelboards for example). HOWEVER it refers back to AALZ as most Category Codes ultimately do. It still says nothing about marking the terminals.

From Category Code QEUY:
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From UL Molded-Case Circuit Breaker (MCCB) Marking and Application Guide, July 2016, page 10, under heading TERMINATIONS...
20. 60/75°C Wire — All circuit breakers rated 125 A or less are marked for use with 60° C, 60/75°C or 75°C only wire. This marking indicates the proper wire size for termination in accordance with Table 310.15(B)(16) of the NEC . It is acceptable to use wire with a higher insulation rating if the ampacity is based on the wire temperature rating marked on the breaker. For breakers rated more than 125 A, the proper wire temperature rating is 75°C and it is optional for the breaker to bear this marking.
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http://www.ul.com/wp-content/uploads/2014/09/CircuitBreaker_MG.pdf
 
We should overview another example here.

30A branch circuit. Utilization equipment doesn't say termination rating. Not a B, C or D motor.

Say we have THHN in conduit. This is a 90C conductor, but by 110.14(C)(1)(a)(2), we must use the 60C column. #10.

Now, if the conductors had derate due to qty current carrying conductors, ambient condition, etc, the 90C rating of this #10 may be used to confirm ampacity. Should the calculated derate be less then the 60C column for the #10, next size up and try again.

Smart $ said:
The 60°C wire is terminated in 75°C-rated equipment that may operate at 61-75°C.

When discussing terminal temperature ratings, it seems many believe the current running through the conductor is the only source of generated heat. However, in enclosures where wire and terminals are not the only equipment, the other equipment can also be the source of heat.
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It seems to me the code takes care of this quite simply by the 100A demarcation. So long as the conditions are met in the code, 60C is used for the ampacity as a conservative measure.

This makes great sense for conductors that are actually rated for 75C and above. The question may then be TW and UF types....to which I am comfortable assuming the code has considered currents below 100A and found them (and the other sources of heat) to be less than the 60C conductor rating; i.e. - 75C termination ratings are excessive for these cases.
 
publicgood said:
...
This makes great sense for conductors that are actually rated for 75C and above. ...

...75C termination ratings are excessive for these cases.
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As I said earlier, this is a matter of listing standard compliance ...not Code... and using physics as a premise will not get us anywhere.
 
Smart $ said:
From UL Molded-Case Circuit Breaker (MCCB) Marking and Application Guide, July 2016, page 10, under heading TERMINATIONS...

http://www.ul.com/wp-content/uploads/2014/09/CircuitBreaker_MG.pdf
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Followup...

From UL Panelboards Marking and Application Guide, July 2016, page 19...
14. TEMPERATURE RATING OF INSTALLED CONDUCTORS

In general, the testing and construction of panelboards are based on the use of 60°C ampacities for
wire size Nos. 14–1 AWG and 75°C ampacities for wire size Nos. 1/0 AWG and larger, taken from
Table 310.15(B)(16) of the NEC, with no adjustment made for correction factors. Panelboards are
marked to indicate temperature ratings and sizes of conductors that can be used.

If the equipment is normally intended for wire sizes within the range 14–1 AWG but is marked 75°C
only or 60/ 75°C, it means that the 75°C wire may be used at full 75°C ampacity.

...
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http://www.ul.com/wp-content/uploads/2014/04/Panelboards_MG.pdf
 
rbalex said:
Again, Yes - So? It still doesn't support your position.
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How does it not support my position???

The only marking options are unmarked or marked 60°C, 60/75°C, and 75°C only. My position is if it is marked 75°C only, you cannot terminate any 60°C-rated conductors in that panelboard. What do you think 75°C only means?
 
Smart $ said:
How does it not support my position???

The only marking options are unmarked or marked 60°C, 60/75°C, and 75°C only. My position is if it is marked 75°C only, you cannot terminate any 60°C-rated conductors in that panelboard. What do you think 75°C only means?
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Because it doesn't say that - it only says when 75°C conductors may be used. It says nothing about using 60°C at their own rating.
 
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