reference methods

cagedanimal2010 · Jul 16, 2010

hi guys,
whats the reference method, of t&e clipped direct to wooden joists above ceiling with insulation??
cheers guys!!

dichroic · Jul 16, 2010

Is the cable totally surrounded by thermal insulation ?

Regards

Dichroic

dichroic · Jul 16, 2010

For a cable likely to be totally surrounded by thermal insulation over a length of more than 0.5 m, the current-carrying capacity is to be taken as the current-carrying capacity for that cable clipped direct to a surface and open (Reference Method C) multiplied by a derating factor (

) for thermal insulation. In the absence of more precise information,

is to be given a value of 0.5.

Tabulated current-carrying capacities for various types of cable installed in a thermally insulating wall or above a thermally insulating ceiling - the cable being in contact with a thermally conductive surface on one side are given in Appendix 4 of BS 7671.

Regards

Dichroic

Guest123 · Jul 16, 2010

It'll either be method 100 or 101 depending on the thickness of the insulation, i.e less than 100mm = method 100, more than 100mm thick = 101.

cagedanimal2010 · Jul 19, 2010

thats what i thought lenny, but keep getting told i'm wrong its "C" .
cheers buddy

JUD · Jul 19, 2010

cagedanimal2010 said:
thats what i thought lenny, but keep getting told i'm wrong its "C" .
cheers buddy

Whoever it is telling you it's wrong, direct their attention to page 265 (Table 4A2) of BS 7671.

Ref. Methods 100 - 103 are specifically for T&E cables in insulation.