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Why can you not replace Micrologic trip unit on the RJ and RL breakers with date codes prior to 09011?

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We have a customer asking about why they can not replace the Micrologic trip unit on the RJ and
RL before 09011.

RJ and RL circuit breakers with Serial Numbers before 09011 should not use field installable Micrologic trip units because there is a chance they may trip slightly outside of the published curves.  Protection is still provided; they just may not trip inside the curve with some LSI settings.

If the trip units have already been changed, you can have Field Services test the trip points of the breakers to make sure they meet the trip curve. If they do with the settings as currently set, they are fine and will work. If they are outside of the band, then the only option is to replace the breakers.

Please refer to document 48049-160-01
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