terminal temp ratings

[Designer69]

You know I used to think when you guys talked about terminal temperature ratings I used to think you meant at the termination equipment not the conductor.

for instance I thought an mcc compartment a motor starter's terminals had different temperature ratings and you had to match the conductor temp ratings to that.

Have I been misinformed this whole time?

 

[480sparky]

Peruse 110.14(C).

 

[Designer69]

thanks sparky, its damn confusing though, it seems like equipment terminations don't have specific temp rating limitations and can handle conductors of various temperature ratings (60, 75, 90deg) as long as the current ratings are in line.

 

[weressl]

thanks sparky, its damn confusing though, it seems like equipment terminations don't have specific temp rating limitations and can handle conductors of various temperature ratings (60, 75, 90deg) as long as the current ratings are in line.

On the contrary, it is the equipment terminals and connectors heat rise temperature rating that limit which column of the 316 tables will you be able to use for a specific type conductor. Additionally a wire may be rated for one temperature rise in dry and to another in wet location. The overall ciruit rating is determined by the lowest rated component, the 'weakest link' in the circuit.

 

[rbalex]

The key is understanding ampacity.

From Art 100 (Definitions):

Ampacity.The current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.

Any wire-type conductor may have multiple ?conditions of use? in a given run; e.g., it may run underground in a duct bank then rise to a cable tray and finally run indoor in a single raceway to the utilization equipment. Of course this is a rather extreme example but the same single conductor may have a different ampacity in each part of the run. Other things, such as the conductor?s insulation, also affect the conductor ampacity. ?Wet? or ?dry? conditions may affect it. And so does the termination.

Terminals are also conductors. Their ampacity/temperature rating is based on the condition of use that they are connected to a wire-type conductor that has its own temperature limitations. Unless otherwise identified, that is a 60C conductor ??for circuits rated 100 amperes or less, or marked for 14 AWG through 1 AWG?? or a 75C conductor ??for circuits rated over 100 amperes, or marked for conductors larger than 1 AWG??

LV Motor terminations are automatically rated to accept 75C conductors, but the other end may still be limited to 60C if it is 100A or less or #14 through #1 AWG.

Medium Voltage terminations have a 90C rating (see Section 110.40) unless otherwise identified.

The entire conductor?s ampacity is then limited to the lowest ampacity created by each relevant condition of use.