Use Of 1.5 And 1.0 Tw&e Together

Is it acceptable practise to run a lighting radial circuit feed in 1.5 mm TWE and the lighting load and switch cable in  1.0 mm TWE whilst protected by 6A MCB. If not why not as cannot find anything in regs that would prohibit such an arrangement.

Thanks.

no problems unless you have really long cable runs and cant meet Zs etc

its fine, but if I do that then I base everything on 1.0mm cable,

sometimes its a way of being able to use existing conduit switch drops but still use 1.5 for derating purposes in loft insulation

Don't know if it'sagainst the regs but I'm not keen. It would be a good idea to leave a note in the CU to prevent future uprating of the MCB by the 1.5mm cable size that will be seen.

I never see the point in using 1.5 for a domestic lighting circuit.   There would have to be a very good reason for me to consider using 1.5 particularly where downlighters are involved where it's hard enough getting two 1mm's into the terminals.

ProDave said:

I never see the point in using 1.5 for a domestic lighting circuit.   There would have to be a very good reason for me to consider using 1.5 particularly where downlighters are involved where it's hard enough getting two 1mm's into the terminals.

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i almost always use 3c 1mm flex for downlights. much easier to work with than T&E

Andy™ said:

i almost always use 3c 1mm flex for downlights. much easier to work with than T&E

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What about 2 core 1mm flex? then you don't have to bother parking the unwanted / unused CPC?

ProDave said:

What about 2 core 1mm flex? then you don't have to bother parking the unwanted / unused CPC?

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dont you have to take a cpc to the point of utilisation whether its needed or not?  [mains downlights of course]

that, Im not sure about, so I could be corrected.

ProDave said:

What about 2 core 1mm flex? then you don't have to bother parking the unwanted / unused CPC?

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depends on situation & wiring method. if they are from a central point, then sometimes use 2 core, if its looped form 1 to another then use 3 core. or for bathroom downlights, sometimes use 2c .75 from a central point to each downlight

Andy™ said:

depends on situation & wiring method. if they are from a central point, then sometimes use 2 core, if its looped form 1 to another then use 3 core. or for bathroom downlights, sometimes use 2c .75 from a central point to each downlight

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why .75 for bathrooms?

If you are talking 12V, then you need bigger cable, not smaller?

steptoe said:

dont you have to take a cpc to the point of utilisation whether its needed or not?  [mains downlights of course]

that, Im not sure about, so I could be corrected.

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Maybe if it's ELV then 2-wire  but with LV I'd run the CPC to the fitting even if it wasn't utilised, at least if will provide some degree of fault protection for the cable itself. 

because i do loads of them, and its usually the same thing each time (and a roll of 2c .75 is cheaper than 1mm 2 or 3 core, especially for the amount i use), just with varying numbers of lights. so i can wire them in bulk away from the job, get there, connect to existing wiring, either push connections into loft or move to a next to a light for future access, place wires ready for new ceiling and done. there also 230v so no problems with higher current

for other rooms, each job is usually different, so normally wired in 3c looping from one light to the next

Thanks for the replies much appreciated glad to read that the consensus with some caveats its o,k.