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Anonymous Poster #1

LV Switchgear - IEC 61439 - Temperature Rise

08/14/2026 11:58 AM

The specification says, " LV Switchgear Bus bar temperature rise shall not exceed 45°C under rated current".

The ambient temperature is around 45°C.

It means the maximum permitted operational temperature under normal service conditions is 90°C (permitted temperature rise + Ambient temperature).

As I understand IEC allows the maximum copper busbar operational temperature under normal service conditions is 105°C.( 35°C ambient + 70°C temperature rise).

Is there anywhere mention the derating factor for the stringent temperature rise than the IEC allowed 7070°C temperature rise?
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#1

Re: LV Switchgear - IEC 61439 - Temperature rise

08/14/2026 12:43 PM

“The specification says…”

Proper and professional business practice dictates that if a referenced model code (in this case, presumed to be IEC) is MORE restrictive than customer specifications, the model code should be used as a minimum.

Proper and professional business practice dictates that if a referenced model code (in this case, presumed to be IEC) is LESS restrictive than customer specifications, the customer specification should be used as a minimum.

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