For a PS3 circuit, does wire insulation inside a fire enclosure have to comply with 6.5.1?
Clause 6.5.1 applies to wiring in all PS2 and PS3 circuits, and the insulation on internal and external wiring is required to pass one of the applicable requirements of that clause. IEC/EN/UL 62368-1 does not provide an exception for wiring inside a fire enclosure.
IEC TC108 is currently working on a revision of the complete clause 6 to clarify requirements of the two existing methods “Reduce the likelihood of ignition” and “Control fire spread” in conjunction with the usage of PIS. There could be some refinement in this area as a result of that work.