Technically speaking, If the manufacturer says only use our breakers then you are suppose to go by the manufacturers directions. Do you have to write them up if there is a breaker in the panel that has been tested for use in that panel but is not of the same manufacturer. I would not.

You must use what is rated for that panel. If what is in there is UL listed then I personally do not see a problem with it.

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Ted Menelly
"Castle"
Home Inspection Services