MCB for 4mm Radial

Discussion in 'Electricians' Talk' started by seavigil, Dec 19, 2003.

  1. seavigil

    seavigil New Member

    Looking at the tables for current carrying capacity of 4 mil T&E, what category is buried under plaster.

    Looking at the worst case this is only 23A which seems a bit low compared to 2.5 mil.

    The planned run will go throught 1.5m floor space throught joists then 4 m clipped onto surface of garage wall then 4 m buried in plaster. Am I correct in thinking that the 4m under plaster is the limiting factor here, in which case a 20A mcb.

    For sockets in a domestic garage is clipped direct ok for cable drop form ceiling to socket.

  2. screwfox

    screwfox New Member

    Clipped direct is fine.

    Where does the cable get buried in plaster?

    Does the cable exit the consumer unit bunched with other cables? If so then a correction factor will have to be applied which will bring the rating down even further
  3. seavigil

    seavigil New Member

    Cable comes out of the consumer unit buried in plaster for about 0.5 m laid side by side then up into the floor/roof space. All other exixting cables also follow this route for the first 0.5 m (6A lights, 30A Ring, 30A cooker, 15A Imm Htr)

    There will be 2 new 4 mm radials going in one, on rcd the other for Fridge/Freezer CH boiler on non rcd, The current load on the non rcd is not an issue but the RCD side will feed washing machine and 1kw Greenhouse heater. Ideally 2 washing machines, but it is looking like a ring is needed for this with a 32A breaker.

    2 washing M/C + 1kw heater could peak at 30A if they were all on at once.

    Alternativley could I feed the 1 kw greenhouse heater off the other radial through its own RCD/FCU, this would share out the load more evenly and would mean that i wouldn't loose the Greenhouse Heater if the washing machine threw the trip.

    The last 4 m will be buried under plaster in the utility room after it leaves the garage.


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