Insulating under upstairs floor, advice about cables please

Hi all.

Kitchen ceiling has a sheet of plasterboard as it's ceiling, the bedroom upstairs gets both smells noise and cold from the kitchen.

The wiring is all rooted through top (or near top) of joists.

I intend to put 4" insulation on the plasterboard, which will under the wiring. But some of the wiring will be resting on the top of the insulation.

My only concerns are both the cooker (6mm I think, might be 10mm) and the immersion heater (2.5mm,, on a 16amp breaker).

The cables run across the top of the joists, above the insulation but at some point will go through the 4" (100 mm) insulation. In other words 4" of these cables will have installation on them. Haven't taken up the floor where the cooker wire is yet, but I imagine it will be similar to the immersion heater.

Pic of immersion cables attached (megaflow tank with two immersion heaters on it, only one used)

is this safe or should I put the 4" of cables in some conduit?

thanks

The cooker wire has a 40 amp fuse on it.

Looking at http://www.cable-ratings.co.uk/

It seems to say my 2.5mm for the immersion when in insulation is 18.5A or 17.5A (not sure why there's 2 columns?) so that having an 16amp breaker, I presume is fine.

My cooker wire is 6mm and not 10mm, it's only rated at 32A or 29A, hence I presume this going through 4" of insulation might be a problem? Or is this talking about a long run being in insulation (presuming there's a difference)?

Many thanks

Your cooker will never take 40a as the rings cycle on and off independently.

You'll struggle getting an airtight seal with insulation boards, you'll get better performance (especially for sound transmission) with rockwool.

If you were contemplating renewing the kitchen ceiling a vapour control layer (polythene) would help a lot with reducing air passage (& thus smells)

Cables through insulation- there's a handy link here https://www.tlc-direct.co.uk/Book/4.3.6.htm.
Short version- if one side of the cable is clipped direct (to wall or timber) or in free air then you're fine.

Thanks. The insulation I’ve got is https://www.wickes.co.uk/Knauf-100mm-Space-Bottom-Layer-Loft-Roll-Insulation---8-3m2/p/166877#

According to the data sheet it’s suitable for insulating between floors.

cant change it for anything else at the moment due to lockdown, so it will have to do

pjo123 said:

Thanks. The insulation I’ve got is https://www.wickes.co.uk/Knauf-100mm-Space-Bottom-Layer-Loft-Roll-Insulation---8-3m2/p/166877#

According to the data sheet it’s suitable for insulating between floors.

cant change it for anything else at the moment due to lockdown, so it will have to do

Click to expand...

My bad, i assumed you were using rigid board. That Wickes stuff will be fine