9.5Kw Shower on-site guisde? 16mm Twin & cpc?

[ian65]

Hi every one,
I should know better but can’t get my head round this one and lost my notes from College.
On site guide is saying up to a 9.7Kw shower the cable CSA should be 16mm this seems rather high to me and impossible to work with.
I am fitting a 9.5Kw shower and looking at smaller CSA than 16 probe’s 10 but this will be for an assessment for a company and has to be correct can some one give me the formula for CSA, the fuse to be used are 40Amp and the total run is 11Meters from consumer unit to the shower.

Thanks Ian.

 

[PC Electrics]

What page number in the OSG says that, please?

 

[Octopus]

10mm will be fine as long as its not run under loft insulation etc.

 

[Electricalserv]

Cable calcs are wonderful things!

 

[pushrod]

Not that your 9.7kW shower is likely to trip it but your shower is theoretically pulling 42A so having it on a 40A breaker doesn't look too good for an assessment. Haven't got any books with me but 6mm clipped direct has a surprisingly high CCC.

 

[ian65]

Thanks for your feedback any more please feel free Thanks Ian.
Electricians guide page 52 under : Upto 9.7Kw Shower and thanks i will find my paper work some where prob's in a cupboard

 

[ian65]

Hi thanks for your reply i was thinking 10 MM minimun but have not had the time to work it out at work, Ian.

 

[SimpleSimon]

What's the run like?

 

[ian65]

Hi and thanks for replying the run is up about 50mm on plastick trunking behind fitted kitchen unit and then to the loft space, this has from what i am told heavey duty lagging but will run over top and then down into a cupboard for switch D/Pole.

I was looking closer at the On site guide and found like a nut i was looking at all the wrong tables untill i got the correct one and i have used Clipped direct method. 2.5 has a 27Amp CCC i am calculating 10 mm should be ample for a 11M run

Thanks Ian.

 

[ian65]

Loft insulation there is and lots of it so i will run it over the top, This is a bungalow i am working in.


Thanks for reply

 

[RWJ]

I was looking closer at the On site guide and found like a nut i was looking at all the wrong tables untill i got the correct one and i have used Clipped direct method. 2.5 has a 27Amp CCC i am calculating 10 mm should be ample for a 11M run

I did say I thought you had the wrong table!!! Still wanted to see you terminate 16mm in to a pull cord... that would have been worth watching!!!

Are you "In" currently Ian.... I'll pop round as I'm headed "up the road"!!

 

[ian65]

As per Instructions with the shower a 40A fuse is to be used.

Thanks Ian.

 

[ian65]

In at min but off to Edmonsons in a bit mate.

 

[Octopus]

On the basis you're going to use 10mm cable and that you will be using a pullcord isolator switch, I'd highly recommend the Crabtree 50A isolator.

 

[rory9214]

10mm sould be fine 11meters is a short run, just avoid going under insulation

 

[JamesBrownLive]

As per Instructions with the shower a 40A fuse is to be used.

Thanks Ian.

As Pushrod has already stated, wouldn't you be better sticking to the regs and using a 45A fuse, rather than following what seems to be the wrong advice in the instructions included with the shower ?

Although the shower manufacturers are probably selling the product as a 9.7Kw unit when in actual fact it is much less
That is probably why they are advocating a 40A protective device. Either that or they are numpties.

 

[JUD]

As Pushrod has already stated, wouldn't you be better sticking to the regs and using a 45A fuse, rather than following what seems to be the wrong advice in the instructions included with the shower ?

Although the shower manufacturers are probably selling the product as a 9.7Kw unit when in actual fact it is much less
That is probably why they are advocating a 40A protective device. Either that or they are numpties.

Some manufacturers still use 240V instead of 230. The shower is probably rated at 9.5Kw at 240V. 9500 ÷ 240 = 39.6A.

 

[UKMeterman]

So what happens when the volts creep up to 253 or 255V?
42A, how will the fuse like that long term with many loading cycles?

 

[malcolmsanford]

To be honest the amount of time the shower will be under load I would imagine that it would cope quite happily with 2 extra amps. Also as the shower runs the load will also go down.

 

[JamesBrownLive]

So what happens when the volts creep up to 253 or 255V?
42A, how will the fuse like that long term with many loading cycles?

Well then the current drawn will actually go down, not up... 9.7Kw / 255v = 38.04A.