Current carrying capacities and vold drop for copper conductors

[Cider]

Hi

Help please with the above.
Using on site guide Im stuck on Cc as I cant find rating factor for 42A type B breaker or is it 1?

Many thanks

Cider

 

[topquark]

What is it you are trying to determine? There is no rating factor for the breaker per se. Rather there is a rating factor that should be applied to the cable the breaker is protecting. The tables start at 274 in the BRB (sorry I don't have my OSG to hand) and will depend on the type of cable used and method of installation.

 

[pushrod]

Hi

Help please with the above.
Using on site guide Im stuck on Cc as I cant find rating factor for 42A type B breaker or is it 1?

Many thanks

Cider

Yes Cc for all protective devices is 1, except for rewireable BS 3036s where it is 0.725

 

[topquark]

Yes Cc for all protective devices is 1, except for rewireable BS 3036s where it is 0.725

Back to school for me again, I'd forgotten that

 

[Cider]

Thanks guys, im trying to work out a cable for an electric shower.
15 mtr run, 9kw shower, 2.5m of trunking, through an insulated cavity wall and then across top of 200mm insulation.
Im getting 53amps

Existing cable is 6mm

 

[pushrod]

As Topquark said earlier, going to depend on installation method. Is it 102 or 103?(see table 4D5 P282 brb) Looks like you're looking at 10mm² T&E at least

 

[Cider]

As Topquark said earlier, going to depend on installation method. Is it 102 or 103?(see table 4D5 P282 brb) Looks like you're looking at 10mm² T&E at least

Its ref meth C but not even cliped as laying over existing loft insulation.
I guess this isnt great as more insulation could be added and a new route should be made with 10mm.

 

[pushrod]

Thanks guys, im trying to work out a cable for an electric shower.
15 mtr run, 9kw shower, 2.5m of trunking, through an insulated cavity wall and then across top of 200mm insulation.

It's not ref method C from what you said above! You take the worst conditions

One way of dealing with the loft insulation problem is making a wooden rail above the insulation fastened to rafters etc and then clipping your cable to that.

 

[Cider]

I was really trying to see if existing 6mm would do the 9kw that a plumber had installed recently. He had clearly not even looked at the manufactures instructions as im quite sure mira instructions are quite comprehensive.
Im quite supprised in the difference between the loads on cable are for a 7-8 and 9 kw shower are when even just passing through an insualated cavity wall.
As the existing is too small then it is easier to just run a new 10mm cable around the edge of the roof and avoid lagging etc.

Thanks for everyones input

Cider

 

[pushrod]

Power ratings of showers are often quoted at 240V so in reality at 230V it can be a smaller current. As someone earlier pointed out 6mm² could be suitable for a 9kW shower, but not in the circumstances you described