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How to interpret the 512.1.5 of BS 7671

eizo

Maybe I’m confused･･･.

I regret to say that I cannot understand the meaning of Regulation 512.1.5. 

Is it possble to interpret the second pargraph and note 3 of Rgulation 512.1.5 as follows? In principle equipment such as circuit breakers must be connected to thermoplastic insulated cables because their maximum operating temprature is 70° C. But the equipment is also allowed to connect to 90° C thermosetting insulated cables provided that when deciding conductor sizes of the cables, a table from Tables 4D1 to 4D4 of Appendix 4 is refered instead of a table from 4H1 to 4H4. 

Any guidance or suggestion will help me.

Thank you.

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  • 0

    Yer wires must not get hot and make yer switchgear hot as well, as that could damage the switchgear etc. A temperature limit of 70 degrees C is set.  The tables referred to are for copper conductors or aluminium conductors. All of those tables referred to are for 70 degree C rated cables.

    The 70 degree C limit is met if 70 deg C tables are used for a 90 degree C cable of similar construction. (Last sentence of the second paragraph).

  • 0 in reply to Zoomup

    Thank you for your reply.

    I will read the last sentence of the second paragraph and condider your whole reply.

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  • 0 in reply to Zoomup

    Thank you for your reply.

    I will read the last sentence of the second paragraph and condider your whole reply.

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