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Compliant?

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Is this arrangement compliant or not?


Consumer unit. R.C.D. protected shower circuit supplied by a B40 M.C.B. which runs to a cord ceiling switch  in the shower room in 6.0mm2 T&E. Old electric shower removed. New power shower installed with water supplied from tanks. 0.63 Amp transformer in loft to feed new integral shower pump motor. Loft transformer fed via 3 Amp fused switched fused connection unit on a 1.0mm2 T&E cable from old shower ceiling cord switch. 1.0 mm2 T&E run 2.5 metres.


P.S. The switched fused connection unit is at the end of the supply cables.


Confirmation or condemnation by regs. please.


Z.
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  • 0

    AJJewsbury:




    Thanks Andy,

                          the 1.0mm2 T&E is running on glass fibre flameproof insulation in a very clean and tidy environment with no rubbish or detritus near it at all. It does not run over any timber joists. I can not see any way that it can be damaged as it is under a tank stand and in an inaccessible area at the end of a loft. 



    A fault can occur in many ways - not just physical damage to the cable. In your situation I'd still be worried about the wiring behind the FCU - a fault there will still expose the full length of the first 1mm² to excessive fault current/duration. I'm sure most of us have come across the results of faults behind sockets or FCUs at some time or other - either from basic insulation having been trapped and squashed, seemingly OK at first but eventually going bang perhaps decades later; or due to loose connection or internal flaw in the accessory causing overheating and melting the insulation. The wiring to the incomer of CUs etc is usually much better than BS 1363 type accessories in that respect as the individual conductors can be run separate from each other and there's no need to squash them all into the backbox after termination, so chances of a fault can be much reduced even if the basic insulation fails. You've certainly satisfied (i) and sounds like you're happy with (iii) as well - but it still sounds to me like you might have a problem with (ii) - and BS 7671 requires all three to be satisfied.


       - Andy.

     




    Thanks Andy,

                              The connections in the fused connection unit in an insulated pattress are perfectly made off. No squeezing or squashing of conductors involved at all in the generously deep pattress. The pattress and accessory are made of flameproof urea formaldehyde. The load is 0.63 Amps maximum and fused at 3 Amp. The transformer is a B.E.A.B. approved type of excellent quality with perhaps an internal over temperature cut out. (I will have to check on that). The supply conductors have "re-enforced" electrical insulation as both are separately electrically insulated. If an earth fault occurs the 30 mA R.C.D. will swiftly disconnect the supply. I think that 434.2.1 (ii) is complied with as a L to N short circuit is almost impossible with this arrangement and very small intermittent load. that will not stress the fused connection unit.


    Also, the 1.0mm2 T&E is only live when the shower is in use, as the users will turn off the ceiling cord switch which supplies it immediately after use, to let the transformer cool down. The transformer has only a 25 per cent duty cycle according to the instructions, 15 minutes use then 45 minutes off to cool they state.


    The shower kit is an Aqualisa kit. The transformer is supplied in the kit and comes from APL Transformers of Westerham, Kent. Type 243501.


    Z.

Reply
  • 0

    AJJewsbury:




    Thanks Andy,

                          the 1.0mm2 T&E is running on glass fibre flameproof insulation in a very clean and tidy environment with no rubbish or detritus near it at all. It does not run over any timber joists. I can not see any way that it can be damaged as it is under a tank stand and in an inaccessible area at the end of a loft. 



    A fault can occur in many ways - not just physical damage to the cable. In your situation I'd still be worried about the wiring behind the FCU - a fault there will still expose the full length of the first 1mm² to excessive fault current/duration. I'm sure most of us have come across the results of faults behind sockets or FCUs at some time or other - either from basic insulation having been trapped and squashed, seemingly OK at first but eventually going bang perhaps decades later; or due to loose connection or internal flaw in the accessory causing overheating and melting the insulation. The wiring to the incomer of CUs etc is usually much better than BS 1363 type accessories in that respect as the individual conductors can be run separate from each other and there's no need to squash them all into the backbox after termination, so chances of a fault can be much reduced even if the basic insulation fails. You've certainly satisfied (i) and sounds like you're happy with (iii) as well - but it still sounds to me like you might have a problem with (ii) - and BS 7671 requires all three to be satisfied.


       - Andy.

     




    Thanks Andy,

                              The connections in the fused connection unit in an insulated pattress are perfectly made off. No squeezing or squashing of conductors involved at all in the generously deep pattress. The pattress and accessory are made of flameproof urea formaldehyde. The load is 0.63 Amps maximum and fused at 3 Amp. The transformer is a B.E.A.B. approved type of excellent quality with perhaps an internal over temperature cut out. (I will have to check on that). The supply conductors have "re-enforced" electrical insulation as both are separately electrically insulated. If an earth fault occurs the 30 mA R.C.D. will swiftly disconnect the supply. I think that 434.2.1 (ii) is complied with as a L to N short circuit is almost impossible with this arrangement and very small intermittent load. that will not stress the fused connection unit.


    Also, the 1.0mm2 T&E is only live when the shower is in use, as the users will turn off the ceiling cord switch which supplies it immediately after use, to let the transformer cool down. The transformer has only a 25 per cent duty cycle according to the instructions, 15 minutes use then 45 minutes off to cool they state.


    The shower kit is an Aqualisa kit. The transformer is supplied in the kit and comes from APL Transformers of Westerham, Kent. Type 243501.


    Z.

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