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installation method slotted PVC trunking

Udtwmc

What installation method would you pick for running single core circuits inside slotted PVC trunking (horizontal and vertical) mounted to a steel gear-plate all enclosed within an electrical control panel assembly that has forced air ventilation (ambient temp controlled <40°C). 

I'm unsure if reference method B (specifically method 6 and 7) is correct being that it says 'enclosed trunking' on masonary or wooden surface, for one that my trunking is slotted (offers some ventilation maybe?) and is mounted to steel (maybe thats worse!?).

Is there an installation method i'm overlooking? hopefully something that will give me more juice!  Could one not get away with saying these cables are clipped direct or in free air on unperforated tray (to the steel gearplate) or is that too ambitious!?

I ask because if i apply all my correction factors (Ca, Cg, 0.97 for class 5 strands) my singles CSA come out at 70mm2 (protection is a 100Amp B type MCB and my design current 87Amps) ...  the SSR's (switches) for these circuits can only take max 50mm2! 

As a comparison, the armoured multicore taking these circuits to the load in the field only needs to be 25mm2 !! i feel i've gone horribly wrong somewhere.

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    First question is does this fall under BS 7671? If it part of a machine or control panel then other standards likely take precedence - and they sometimes have differing approaches to cable installation methods.

    Unsheathed singles in slotted trunking wouldn't be an normal BS 7671 installation method - as the trunking typically wouldn't meet the IP4X requirement (although it might technically pass IPXXD, but expect raised eyebrows about the spirit of that). That might not be relevant if its inside an electrical enclosure though - again pointing to BS 7671 not really being the ideal standard.

       - Andy.

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  • 0

    First question is does this fall under BS 7671? If it part of a machine or control panel then other standards likely take precedence - and they sometimes have differing approaches to cable installation methods.

    Unsheathed singles in slotted trunking wouldn't be an normal BS 7671 installation method - as the trunking typically wouldn't meet the IP4X requirement (although it might technically pass IPXXD, but expect raised eyebrows about the spirit of that). That might not be relevant if its inside an electrical enclosure though - again pointing to BS 7671 not really being the ideal standard.

       - Andy.

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