MV-105 Cable Ampacity Temperature Limitations

[rockman7892]

Are there applications where it is permissible for use MV-105 cable at the listed 105C temperature rating? My understanding has always been that the 105 deg C rating could be used for de-rating purposes however cable was limited to 90deg C rating due to MV terminations being listed for 90C?

If 90C is temperature limitation is this due to cable terminations themselves or the bus or equipment where cable is terminating (ie switcher). I’ve seen some cable termination kits that appear to be listed for 105C

 

[waross]

Mostly device terminations.
Some breaker terminations were temperature rated for 75 degrees.
As I recall, the Canadian Electrical Code gives a minimum length for pigtails attached to cables operated at higher temperatures.
For example, an 250 kcmil cable rated and used at 400 Amps at 110 degrees may be connected to a 75 degree rated breaker by a 400 kcmil cable rated for 425 Amps at 75 degrees,
In the real world, the AHJ will generally pass a 350 kcmil cable rated at 395 Amps at 75 degrees.

Another instance where the higher temperature rating is used is where the current is below the 75 degree rating but the cable must pass through an area of high ambient temperatures.

If the cable is used at a current rating higher than the 75 degree rating to connect to a thermal or thermal/magnetic breaker rated for 75 degree cables, the breaker calibration may be compromised.
Other devices may similar temperature issues.

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Ohm's law
Not just a good idea;
It's the LAW!