Installing a 10.8kw Shower

[Killeavy]

Hi
I am going to install a 10.8kw shower. I have been getting contradictory advice as to size of cable and fuse rating. Can anyone help? I was going to install using 10mm T&E and also fit an RCD. I was also going to use a 45A fuse at the consumer unit. I have found on certain sites that i should be using 16mm T&E and it should be governed by a 50A fuse. There's no way i will get 16mm into the shower unit. The consumer unit is rated at maximum of 63A. The length of the cabe le run is approx 15 metres from CU to pull cord switch. Any help greatly appreciated.

 

[PartPapproved]

10.8KW = 47 amps @230 vlts so mcb should be 50 amps , you say run is 15 m to pull cord so lets say total run is 17m voltage drop is 3.52 amps = 0.02% so thats all okay now for the fun bit 10mm t/e has a max clipped direct rating of 64amps however it must be remembered that clipped direct means what it says and this is very often difficult to achieve in domestic situations unless you can clip direct all along the complete run then i would rate the cable at 52amps but be careful that the cable is not grouped with others and is kept separate along its run. All in all you should be ok with the 10mm cable.

 

[Adam_151]

10.8KW = 47 amps @230 vlts.

I challenge you to find such a shower, a fiver says its 10.8kw @ 240v and 9.9kw @ 230v

 

[PartPapproved]

Yeah right i was working off of his figures! ie no make or model number

 

[securespark]

No 63A CU should host a circuit greater than 32A.

Also, I personally would rate the installation method as 15 where the cable is in contact with thermal insulation - most shower cables are in contact with it for at least 500mm.

This puts 10mm2 down to 47A.

 

[jondiy]

But surely, if its a flat (or even a small house) , that does'nt have other major circuits (eg cooker circuit), then surely, it could be possible to add it , i mean if the householder knew that the shower used most of the capacity of the circuit, then he/she could just make sure they shower whilst not using other major loads simulataneously, eg electric fire/kettles/etc.

If you are worried about the loading, I'd reccomend a seperate shower consumer unit, running alongside your cu. Obviously, its now part p, so technically you won't be able to do it yourself as it involves using henley blocks from the meter tails, and unless you have a DP isolator, you'd have to pull the service fuse (which is also illegal), so you'd have to get a part p electrician to install it all for you. You would have no load problems with this method - in fact, it could be possible to blow the service fuse if you were running a max load on your consumer (63 amps) , and showering at 47 amps, so again, you'd still have to be careful, although not as careful as you'd have to be if you opted for the original method.

So how big is your house (eg how many circuits are you running on the consumer? , anything major/minor??) , that should decide which option to go down.

 

[securespark]

Consumer Units with a sub-100A main switch were never designed for any circuit greater than 32A.

Look at the old Wylex Standard range. Now look at the fuse carrier for a 40A breaker. On the back is a little tab which makes fitting it correctly to an older board impossible.

Yes, a sep cu is an option, but if you don't have an RCD already, it may be prudent to replace with a S/L board.

 

[plugwash]

the low rated wylex standards weren't i'll grant you that. but afaict in modern modular CUs the bussbars are a standard size regardless of what incomer happens to be fitted.

 

[Steve]

you'd have to pull the service fuse (which is also illegal), so you'd have to get a part p electrician to install it all for you. You would have no load problems with this method - in fact, it could be possible to blow the service fuse if you were running a max load on your consumer (63 amps) , and showering at 47 amps, so again, you'd still have to be careful, although not as careful as you'd have to be if you opted for the original method.

part p is not a qualification for someone to pull a service fuse - only the DNO can legally pull it. This is why only they carry seals for fuses and meters.

And do you know that his service fuse isn't 40A? Unlikely, i know, but it could be any one of 40, 60, 80 and 100A.

 

[jondiy]

I did'nt say that a partp qulified would be able to remove the fuse!! I just said that you would need a part p qualified to install the seperate shower consumer unit for him!!

Yes agreed, the service fuse could be 40A, but then you can always request the DNO to upgrade it, I mean what use would be a brand new split c/u with a full load of circuits including shower and cooker, and a 100 amp main switch , if you only had a 40 amp service fuse!

Was only giving my general views and advice. About 18 months ago I installed a seperate shower cu for a friend & a 10kW shower , who was (and still is) running an old Wylex board with a 60 amp switch. They've had no problems with this setup and have never blown the service fuse.

The reason the original poster would llike to use one is because it will solve his problem (and has rcd protection) , and only costs about £20 + tails,henleys etc , whereas a new cu with rcd and a nice load of mcb's would cost £60 minimum and take longer to install.

Crafty 1289, are you part p registered, just for the record??

 

[Steve]

No i'm a DIYer. Hoping to become a spark myself soon though!