Running 2.5 ring main cable under a floor & over a ceiling

[jim]

Please, what is the correct method of installing a 2.5mm2 ring main cable under a bedroom floor?

The floor void is 150mm deep with timber joists on 400mm centres. Underneath is a 12mm plasterboard ceiling. The void is mostly filled with fibre glass insulation, hence my concern about thermal insulation in close proximity to the cable.

Possibilities seem to be:

1. Lay it flat on the plasterboard

1. Pin it to the side of a joist with Tower clips - but if so how deeply down the joist? Does a 50mm clearance below the floor (which the clearance specified for cable passing through a joist to avoid nail penetration) have to be allowed?

2. Run it in mini-trunking or some other type of conduit?

1. Some other way? Going round the room above floor level is not a practical proposition.

In any case what would be considered the normal method if the fibre glass were not present?

TIA for help & advice.

[cynic]

For a proper answer not a suggestion from someone you have never met. You really need to take a trip down to your local reference library and consult the On Site Guide to BS7671 - in particular table 7.3 on page 53 and table 7.1 on page 44 This suggests standard installation method 100 or more likely method 101 and the current rating of the cable can be seen in 4D5 of the main regs if you look. Personally I would lay the cable on the plasterboard. Dropping the rating of the circuit breaker might be advisable or you could use 4mm cable depending on the likely loading of the circuit. Are you au fait with the building regs requirements for drilling or notching joists? If not try the same On Site Guide fig 7.1

[ARWadsworth]

We have some of that info in the wiki.

?title=Cables#Installation_MethodsCheers