Wiring 4 storey house hopefully using this job for niceic assessment
Looking for some advice on cable runs etc in loft area and down cavities.
Firstly the loft will have 300mm insulation put in ,basically looking for best way to lay cables according to regs as the insulation will be in last,
Secondly , existing external walls are being built out about a 25-50mm with existing walls staying intact (gyproc) so looking to see what kind of protection required for cables
Internal walls are just being finished off plastered etc so fishing down to switch points , everything to be wired from loft , and ring main will be mainly vertically run apart from going back up loft and down to stop cables running through ensuite
Any advice appreciated from my questions and any pointers on niceic
If I was an assessor I might ask "how have you supported the cables in the cavity"
Another might be "how have you avoided damage to the cables in the cavity"
Or "have you taken into account the cavity insulation for cable calcs"
Then there is "how have you over come the possibility of moisture crossing the cavity on your cables"
:wink5:
no one has cocked up
the external walls are being built out so the cabling will be on the existing surface and will be clipped with spacing of 50mm to the surface
internal walls wont be adjusted ,
this is only for the top level of the house , lifting floors is not practical or even possible,
I think I see. your cables will be clip on what is currently the external face of the property, at a later date a new outer wall is going to be built up from ground level forming a new cavity, in essence the place will have 2x cavities.
YES (NOT CLEVER) THAT IS IT , AND ALL WIRING WILL BE FROM LOFT AREA
THE RING MAIN WILL COME UP CABLE VOID TO TOP FLOOR AND RUN VERTICALLY UNTIL WE COME TO THE ENSUITE AND WILL GO BACK UPTO LOFT AND DOWN AGAIN (i think this is best if not let me know)
so in all sockets 90% vertically run from socket to socket and when easier we will go back upto loft.
lights are all from loft and switch drops will be from loft area down existing cavity in internal walls .
im basically looking for some guidance on mechanical protection and runs for the cables in loft
No need to shout fella people are only trying to understand fully before they respond.
In an attic space the thing that you need to take into consideration is insulation and the possibility that the cables may run through it, if you deem that the cables will run in insulation that has a depth of 100mm or greater then you need to either derate the fuse size of the new ring final circuit or alternatively upgrade the the cable size to be used from 2.5mm t+e to 4.0mm t+e and this will then satisfy BS7671 aslong as the circuit size is 100m sq or less. You should also satify BS7671 with regard to securing the cables.
You can run the circuit within mechanical protection but to be honest it will not be as cost effective as upgrading the cable size.
what about having the cable clipped in loft along the beams so that it would be above joist level .
the insulation is due to be 300mm thick.
there is going to be fire rated downlights in the ceiling also what measures would need to be taken with regards to the insulation covering the downlights
Option 1:
SWA submain on tray from ground floor & put a small cu on top floor.
Circuits from cu, up into loft then do as you say drop to each point.
Bin the ring main go for a radial & use JB's in the loft that way you can get away with a single drop to sockets & use 20mm conduit down to a box, out back of box through the wall to socket.
ensuite having a shower ?
Will probably work out the cheapest option.
Option 2:
50x50 galv trunk from ground floor up to loft & take circuits up that (still think you'll have issues with cable support if assessor asks about your method) & then run as you have said but use 25mm conduit for the drops to outlets if you are still wanting to use a ring (remember VD three storeys is a long way)
What ever option you do you'll need to think of cavity insulation when doing your cable calcs.
Me I'd go with 1 (its what I tend to do for loft conversions)
Cables in the loft, nail a 6x1 round the trusses above the insulation & clip to that, clear insulation away from where you take the cable drops.
what about having the cable clipped in loft along the beams so that it would be above joist level .
the insulation is due to be 300mm thick.
there is going to be fire rated downlights in the ceiling also what measures would need to be taken with regards to the insulation covering the downlights
the way the house is the main board is on ground level and straight above that is the top floor, its staged out floors its not 1,2,3,4 straight up its set out left to right each floor and has 1 set stairs to each 5-6steps so the ring will be 80meters max .
i cant see the need for cable tray with sub main in this instance my fault for not explaining correct in essence the top floor is 1 up but has 1 floor inbetween 1 stair up and down
im basically asking for advice on the loft area as there is no insulation but will be 300mm of insulation going in at later date.
i know the cabling on external walls is sufficient as it will be protected my rcd , will be more than 50mm from the surface and cables will be run horizontally/vertically to any accessory or D/B and will be within 150mm from where ceiling meets wall and wall meets wall in corner.
i will be using 2.5mm t&e on ring protected with 32a circuit breaker length of run is 80 meters max
loft cabling can be run above the level of the insulation and where it drops through the itchy poo, a bit of drainpipe around it will suffice. for your downlighters, use LED lamps.
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