Equipment/ terminal temperature ratings

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How to properly size conductors based on insulation and termination temperature ratings is an often discussed topic among PV designers. Those discussions have provided clarity and understanding of the issue but determining equipment rating, as opposed to termination rating, is still unclear

1. If a piece of equipment contains any individual components that are rated for 75deg is it still possible to for the overall rating to be 90deg? Presumably, relative location/distance of 75deg-rated components may allow for sufficient heat dissipation between components.
2. If a piece of equipment does not have a temperature explicitly marked on it's exterior is there an implied rating? 75deg? 60deg?
3. Are ratings determined by a specific UL test or are they manufacturer specified?
4. Is there a specific distance of separation required between two differently rated pieces of equipment and/or terminations? Certain equipment manufacturers have stated that an extended terminal protruding from a 75deg-rated component would allow for a 90deg-rated lug and 90deg conductor sizing.
5. Square D documentation indicates that all 600 V equipment is either 60 or 75deg-rated. Is this true? Referenced documentation is 11 years old. Perhaps this has changed?
1. Pertinent excerpt: 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.

 

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1. If a piece of equipment contains any individual components that are rated for 75deg is it still possible to for the overall rating to be 90deg? Presumably, relative location/distance of 75deg-rated components may allow for sufficient heat dissipation between components.

Doubtful if not impossible.

Unless something has changed you will not find equipment under 600 volts rated above 75C

2. If a piece of equipment does not have a temperature explicitly marked on it's exterior is there an implied rating? 75deg? 60deg?

If it is not marked the rules of 110.14(C)(1) kick in which in a nutshell limit us to 60C under 100 amps and up to 75C above 100 amps.

3. Are ratings determined by a specific UL test or are they manufacturer specified?

I don't know.

4. Is there a specific distance of separation required between two differently rated pieces of equipment and/or terminations? Certain equipment manufacturers have stated that an extended terminal protruding from a 75deg-rated component would allow for a 90deg-rated lug and 90deg conductor sizing.

Gray area, but the equipment would have to be listed for 90C and I don't think you will find that.

However, you could run 75C sized conductors away from the equipment and splice to 90 C sized conductors using a termination rated for more than 90C.

5. Square D documentation indicates that all 600 V equipment is either 60 or 75deg-rated. Is this true? Referenced documentation is 11 years old. Perhaps this has changed?
1. Pertinent excerpt: 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.

As far as I know that has not changed and I don't expect it will. The general direction lately has been to be more conservative with conductor ampacities. This is evidenced by the newer rules regarding conductors on roof tops and run through holes with thermal insulation.