- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
I was sent a private message asking about the use of 90C insulation and why it must always be applied to equipment based on the 75C column of NEC tables. I think the answer would be of value to many people, so I am replying in the Form.
The primary reason is the way UL tests temperature rise at terminations. The conductor is actually used as a heat shink during their tests.
The following quote is taken from a Square D publication that cover wire terminations.
"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. This
includes distribution equipment, wiring devices, transformers, motor control
devices, and even utilization equipment such as HVAC, motors, and light
fixtures."
For more information go to:
http://www.squared.com/us/products/gendoc.nsf/07a0210021262d45862564b5006e4f84/7e3f70f8decb27da85256b8a00700e48/$FILE/0110DB9901R2-02.pdf
The primary reason is the way UL tests temperature rise at terminations. The conductor is actually used as a heat shink during their tests.
The following quote is taken from a Square D publication that cover wire terminations.
"For electrical equipment rated for 600 V and less, terminations are typically
rated at 60 ?C, 75 ?C or 60/75 ?C. No distribution or utilization equipment is
listed and identified for the use of 90 ?C wire at its 90 ?C ampacity. This
includes distribution equipment, wiring devices, transformers, motor control
devices, and even utilization equipment such as HVAC, motors, and light
fixtures."
For more information go to:
http://www.squared.com/us/products/gendoc.nsf/07a0210021262d45862564b5006e4f84/7e3f70f8decb27da85256b8a00700e48/$FILE/0110DB9901R2-02.pdf