Worried about my girth! Is 10 mm2 enough for 10.8 kw?

[obmitty]

Hi,

I want to install a 10.8kw shower, covering the cable in plaster, and sharing part of the route (3 meters) with a ring main (both wires), and 3 meters with an extractor fan spur (2.5mm cable). 3 meters under loft insulation. Total length of cable <13 meters.

Will a 10 mm2 cable suffice?

Is it worth moving the cables to run separately?

Also the wall the wire will be incased in is in Zone 3. Is that a problem?

Many Thanks!

 

[C&GStudent]

You have to do your cable calculations. Look in your regs appendix 4!!

Why are you worrying about cable inside a wall in Zone 3? Your shower is in Zone 1.

 

[davy_owen_88]

3 meters under loft insulation.

Pull it clear of the insulation and clip it to the joists and you'll have no problem with 10mm² t&e.

If you have to have it under the insulation you will need to use 16mm² at a minimum.

 

[obmitty]

So, if I pin the cable above the insulation will that save me?

I have already bought the cable, so if not could I just add another 10mm2 cable to the one already run and be safe?


Is there a website that helps you with these calculations?

 

[comms]

http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

 

[Chri5]

10mm sq is fine

You MUST provide a trunking route or surface clip to use this cable on a 13m run. I'd suggest MT4 40mmx 25mm which has loads of air space.

I want to install a 10.8kw shower, covering the cable in plaster, and sharing part of the route (3 meters) with a ring main (both wires), and 3 meters with an extractor fan spur (2.5mm cable). 3 meters under loft insulation. Total length of cable <13 meters.

Deep chase the wall and fit the trunking and bury it.
Keep the 10mm sq as the only cable in the trunking.
Lay the trunking over the insulation rather than under it.

 

[Chri5]

You have to do your cable calculations. Look in your regs appendix 4!!

C&G

Your answer is about as helpful as a chocolate fire barrier .

Funny, since I've seen plenty of your posts and peeps here have been more than helpful to you, could you not attempt a bit of humility and reciprocation?

Failing that, if you won't answer a post, please don't post unhelpful, time wasting post responses of no use to anyone.

 

[obmitty]

Its helpful tips like that that the regs will never help you with. However, will an inspector see this trunking + air space as "in" a wall or outside?

 

[Chri5]

It's irrelevant, it's inside the trunking and by over sizing the trunking:-

40 x 25 = 1000 mm sq, cable is about 120mm sq in sheath.

More than plenty air space, ambient temp 20 deg C, no grouping factor.


Lets see if any of the site guru's such as C&G want to come back with other considerations

 

[Steve]

3 meters under loft insulation

Thats A LOT of loft insulation!

 

[securespark]

No, I think he means it runs along horizontally under 3m of insulation, not 3m depth of insulation.

 

[Steve]

No, I think he means it runs along horizontally under 3m of insulation, not 3m depth of insulation.

I know. where's your SOH today Simon?

 

[ricicle]

10mm sq is fine

You MUST provide a trunking route or surface clip to use this cable on a 13m run. I'd suggest MT4 40mmx 25mm which has loads of air space.

I want to install a 10.8kw shower, covering the cable in plaster, and sharing part of the route (3 meters) with a ring main (both wires), and 3 meters with an extractor fan spur (2.5mm cable). 3 meters under loft insulation. Total length of cable <13 meters.

Deep chase the wall and fit the trunking and bury it.
Keep the 10mm sq as the only cable in the trunking.
Lay the trunking over the insulation rather than under it.

Why put the cable in trunking.It will be fine sheathed in plaster.

 

[obmitty]

Why put the cable in trunking.It will be fine sheathed in plaster.[/quote]

The calculation on the link pasted above says otherwise. 16mm if in plaster for that length. I have a 10 mm cable already.

 

[ricicle]

Why put the cable in trunking.It will be fine sheathed in plaster.

The calculation on the link pasted above says otherwise. 16mm if in plaster for that length. I have a 10 mm cable already.[/quote]

That is for a thermally insulated wall.Enclosed in building materials eg plaster is method 1 same as clipped direct so therefore sheathing under plaster is fine.

Methinks chri5 needs to read his regs book before he goes to bed at night