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How can the amp rating of a P frame, R frame, or Masterpact NT or NW circuit breaker be changed?

Issue:
Can I make a breaker trip at a different amp rating?

Product Line:
Circuit Breakers

Resolution:
For the above breakers and trip units, the long time amp rating can be adjusted by these methods (also reference the below picture):
(1) ADJUST THE RATING PLUG IR DIAL - The trip unit has a rating plug Ir dial with various settings, typically from 0.4 to 1.0, which, when multiplied by the sensor plug In value, gives the breaker its long time rating. Simply adjusting the rating plug Ir dial to another value sets the breaker to a different long time rating.
(2) CHANGE THE SENSOR PLUG - The breaker has a sensor plug, which shows an In sensor rating value on it. The In value is the absolute maximum long time rating of that breaker. Changing the sensor plug to a different one of lower In value (50% of the original sensor plug at minimum) changes the long time rating of the breaker.
(3) BOTH OF THE ABOVE - At the same time, adjusting the rating plug and changing the sensor plug will give you a large variety of long time ratings.

Example #1
What are the minimum and maximum long time ratings of a Powerpact 800 A breaker with 5.0 trip unit and rating plug A?
  • For the minimum, adjust the rating plug Ir dial to 0.4 and multiply that by the sensor plug value (In = 800 A) to get the minimum rating of 320 A (0.4 x 800 A).
  • For the maximum, adjust the rating plug Ir dial to 1.0, and multiply that by the sensor plug value (In = 800 A) to get the maximum rating of 800 A (1.0 x 800 A).
Example #2
What are the minimum and maximum long time ratings of a Powerpact 800 A breaker with 5.0 trip unit with rating plug A, after the sensor plug has been changed to 400 A?
  • For the minimum, adjust the rating plug Ir dial to 0.4 and multiply that by the new sensor plug value (In = 400 A) to get the minimum rating of 160 A (0.4 x 400 A).
  • For the maximum, adjust the rating plug Ir dial to 1.0 and multiply that by the new sensor plug value (In = 400A) to get the maximum rating of 400 A (1.0 x 400 A).

Note: To meet NEC 240-6(C), after adjusting the rating plug Ir dial, install the MICROTUSEAL Wire Seal Kit for Micrologic Trip Units. This seals the cover over the rating plug Ir dial.

Picture of dials

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