T&E under the floor

[Duncan Bennett]

Cab anyone help me with a reference method for T&E running under the floor in a domestic situation?

Also, I assume that the reference method applies to the method that describes/applies to the longest section of the run. I have a 1mm cable running on the surface (1 metre) from the CU, then through a ceiling into the floor above, running beneath the boards for about 2M, then up a service void, then over the ceiling (under insulation) to a joint box distributing to the lights.

I've boiled it down to B, D & C thus far using tables 4A2 & 4D5. But there are so many other general options :sick:

 

[frank3323]

normally for cable calcs i would use the reference method of the longest part of the run but if it is running in insualtion i would use table 4D5 as this will account for the extra ambient temp and the fact it is a T&E.

 

[Silly Sausage]

I would say 100 or 101, see the end of 4A2.

 

[malcolmsanford]

Have a read of Reg 523.9 and it will reveal all

 

[Duncan Bennett]

Thanks, all :teeth_smile:

I had intended to use 101 as it accounts for the longest section of the run, but I just wondered - as I can't find a specific reference method for running under floorboards (other than in soil or cement troughs), what would be the closest method. In the case of a ring circuit, practically the entire run can be under a floor, and that might include running through holes/slots in the joists and being buried in deafening.

 

[Silly Sausage]

I think I'd say that's clipped direct...assuming the space is empty.
What do you mean "and being buried in deafening"?

 

[kellogs64]

i thought it was yhe worst case not the longest run i.e if it runs through insulation longer than 500mm then your correction factor is .5

 

[Richard Burns]

Thanks, all :teeth_smile:

I had intended to use 101 as it accounts for the longest section of the run, but I just wondered - as I can't find a specific reference method for running under floorboards (other than in soil or cement troughs), what would be the closest method. In the case of a ring circuit, practically the entire run can be under a floor, and that might include running through holes/slots in the joists and being buried in deafening.

Under a floor I would say would be the same as installation method number 47 in 4A2 "in a ceiling void or suspended floor", reference method B.

 

[Duncan Bennett]

i thought it was yhe worst case not the longest run i.e if it runs through insulation longer than 500mm then your correction factor is .5

I've been asked that one before, Kellogs. Much of Edinburgh (where I did of my time) has the roof/ceiling voids of the tenement flats filled with cinders which came from the Portobello coal-fired power station (long since gone now). This is called 'deafening' as it was supposed to muffle the sounds from the flat upstairs in the days when bare boards and linoleum were popular. Working down the way: you had the floor boards, then a layer of deafening, then the deafening boards, then the lathe and plaster ceiling of the house below.

It was murderous stuff to work with; it wasn't uncommon for the deafening to come to top of the joist so, in order to bore the joists and run the cable, you had to dig the stuff out and it could rip your hands to bits if you weren't careful.