Breaker Operation

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captainwireman

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USA, mostly.
If the breaker panel (residential, MCCB, inverse time or for that matter GFCI or AFCI) is located in a -40 degree F ambient temperature environment but the circuit conductors are in a heated 72 degree F residence, would they still provide the same protection as if they are at the same ambient temperature?
 
-40 is the low end of the range for many specs and below the range of many specs. First thing I would do is research the specs on the equipment to see if they're even rated for that environment. They probably are, but as stated, that's right at the bottom; best to make sure.

A thermal trip obviously won't react as quickly in the colder environment, but what saeth the pros on here about magnetic trip? Same as if in same environment? I can see adding a few ms but the trip threshold should not change, right?
 
Right. Except for possible effects on the characteristics of the springs, etc. there should be no effect on the magnetic trip characteristics.
The thermal trip curve will definitely move toward higher current at each time line.

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