Splitting supply to a shower!!!

carhartt kid · Post by **carhartt kid** » Tue Dec 26, 2006 1:44 pm

If you all are a bit bored then I'll chime in with a question...

I've got a 10mm cable coming from my consumer unit to my bathroom. Its was fitted to an old shower i've just taken out! The previous installer had this cable running to a pull cord on the ceiling and then another length of 10mm going to the shower unit itself. So the pullcord interrupts both Live and Neutral!

The pullcord is above what is now the bath and so i've had to move it to the other side of the room. Rather than running a new lenght of cable from the consumer unit up to the new position of the pullcord and then back to th shower. Can I run the Neutral straight up to the shower and under the floor boards, use a spare waterproof 30amp Heavy-Duty junction box to split off the live across the room, up to the pullcord and back to the shower?????

Hope this makes sense?????

Thanks boys... Oh and guess what i've got for tea...Turkey and Ham pie!!!!! With Reheated veg!!! God help us all!!!!

Jaeger_S2k · Post by **Jaeger_S2k** » Tue Dec 26, 2006 9:37 pm

Amen!

Think for showers/power in the bathroom both should be switched, but a sparkie (probably some dude) will be along soon.

I'm not sure I follow your plan?

Is this bathroom in a flat, so no loft space above?

carhartt kid · Post by **carhartt kid** » Tue Dec 26, 2006 10:25 pm

This is the idea????

sparkydude · Post by **sparkydude** » Tue Dec 26, 2006 10:47 pm

Sorry carhart, but the isolation switch should break live and neutral, just live alone is not enough. Besides you would have single cores running around without double insulation or an earth with them in your way of wiring. There is another way, to make it easier, It involves using a contactor to operate the shower, but if you have not got one then iots about £20-30 To buy . Let me know if you want o run with this idea, as it would mean you can use just a 1.5mm t+e to isolate the shower and you can use a normal pulllcord suitable for lighting to do it.

Nick

carhartt kid · Post by **carhartt kid** » Tue Dec 26, 2006 11:04 pm

Ahhh I thought that was the case.... Both Live and Neutral having to be switched. That was why I was checking...

So I've gotta run 10mm from where it enters the room...across under the floor, up the wall... to a pullcord...then back down, across the floor and up to my shower.

I was just tryin to save a few quid on cable as I'm totally skint and 12 metres of 10mm's not something I have to use when working!!!

One last quickie..Do I have to use 10mm?????

Hinton Heating · Post by **Hinton Heating** » Wed Dec 27, 2006 12:02 am

what Kw size is your new shower?

carhartt kid · Post by **carhartt kid** » Wed Dec 27, 2006 1:43 am

Not sure yet hinton. Just finished the plumbing and plastering, and have buried a cold water supply and a piece of cable to a double patress, with aflush late on it. Might even tile over it till i can afford a shower unit. So just coverin my ass really!

Also, I'm skint because a most of the work I did in Dec, either paid late or haven't paid yet..So am a bit skint!!! Feckers!!!!!!!!!

Anyways, got my free tickets to Deal or No Deal t-other day, so I'm a happy chippy!!!

Hinton Heating · Post by **Hinton Heating** » Wed Dec 27, 2006 1:56 am

The Kw size of the shower will determine the size of the cable.

I'm sure a sparky will let us know what amperage each size able will give.

To find the amps, divide the watts by 240.

eg 11.5 kw shower = 11500w divide 240v = 47.92 Amp

Hinton Heating · Post by **Hinton Heating** » Wed Dec 27, 2006 1:58 am

I found this... (will try find more complete table)

Conductor Size : Current Maximum : power (Watts)

0.5 mm2 : 3 amps : Up to 720 Watts
0.75 mm2 : 6 amps : Up to 1440 Watts
1.0 mm2 : 10 amps : Up to 2400 Watts
1.25 mm2 : 13 amps : Up to 3120 Watts
1.5 mm2 : 15 amps : Up to 3600 Watts
2.5 mm2 : 20 amps : Up to 4800 Watts
4.0 mm2 : 25 amps : Up to 6000 Watts

sparkydude · Post by **sparkydude** » Wed Dec 27, 2006 6:41 am

If your circuit you are extending onto is 10mm then you will need to carry it on with 10mm, if its 6mm, then continue with 6mm. Otherwise when you come to have it tested by your sparks he will most likeley fail it due to it changing sizes along the line and might think you have done a dodgy joint in it somewhere. Also dont forget cross bonding in your bathroom,linking, hot,cold,towel rail/radiator if present,metallic light fitting,shaver point and shower together with a loop of 4mm green/yellow insulated cable. You will not be able to do it as in your drawing as you will not get a 6 terminal junction box in that size to extend your 10mms so your best bet is a plastic adaptable box, with stuffing glands fitted and then getting a sparky to through crimp the cables in there as you are not really meant to have connections that are not available for inspection buried under floorboards.

Nick

Hinton Heating · Post by **Hinton Heating** » Wed Dec 27, 2006 10:22 am

NIck, can you extend the table to give 6mm & 10mm cable ratings?

carhartt kid · Post by **carhartt kid** » Wed Dec 27, 2006 2:53 pm

Just measured the cable and its 6mm (thats 5 x 1mm strands in a harmonised sheath, then a 1mm outer grey sheath)...

I've got two IP67 rated 90mm junction boxes, with waterproof glands and internal earth stud and ring, that I'll connectiong the new cable to the old.

http://www.screwfix.com/app/sfd/cat/lrg ... l&ts=31581

Or I may use the old BS6220 30amp 3 terminal heavy duty box?

http://www.screwfix.com/app/sfd/cat/lrg ... l&ts=31668

Also the bonding for the bath, basin and the towel radiator is all on a 6mm green and yellow that goes back to the consumer unit all by itself... It was supposed to be for the bonding of the old bathroom buth the previous owner didn't use it and just left it rolled up under the floor boards..

tim'll fix it · Post by **tim'll fix it** » Wed Dec 27, 2006 3:12 pm

250V x 30A = 7.5KW

so really a 30 A JB is too small

as for the bonding my spark tells me to bond, basin, bath and rad using 4mm earth back to the light fitting

Post by **ultimatehandyman** » Wed Dec 27, 2006 3:26 pm

You can get higher ampage junction boxes-

http://www.tlc-direct.co.uk/Products/AAJB60.html

As for the bonding, you need to connect the light and shower earths to the earth on the existing metal pipes and anything else that is electrical, such as a shaver socket etc. 4mm green and yellow earth wire is normally used to do this.

sparkydude · Post by **sparkydude** » Wed Dec 27, 2006 5:50 pm

Tim, you are now meant to use 230V as your calculation voltage, not 240 or 250, as i suppose the way they look at it is if you work it out with 230V thats the worst case scenario, cant get worse than that really.

As for the table mr hinton, that table relates to flexible cables only , as you cannot obtain 1.25mm twin and earth LoL, any cable which has fine stranded cores, has a slightly higher current carrying capacity than a normal stranded core cable.
Will try and find a table somwhere which shows the sizes and ratings.
You cannot use those first joints in your picture, they are only suitable for flexes on pond pumops etc, No way will you get 10mm Twin into them, You will also struggle with 30A Junction boxes, so if i was you either buy an adaptable box and then some 60A connector block to put inside it, or some 60A junction boxes as UHM showed in his link

Nick