Utilise an existing 10mm cable for 3amp towl rail.

[David Catherall]

Hi,

Is there any reason I can't use an existing run of 10mm twin/Earth for an electric towel rail. An electric shower has been removed but I'm thinking, rather than running a spur off the ring, I can just use the existing 10mm run but change the MCB to a 3amp instead.

Is there anything in the regulations to say that this shouldn't be done?

Thanks.

 

[winston1]

If you can get your 10mm cable into your towel rail OK. Doubt you'll find a 3 amp MCB but the existing whatever size one is to protect the 10mm cable only which it will still do. If you like you could use a 6 amp one.

 

[JohnD]

use an FCU with flex outlet. The flex to the heater will fit the terminals easily enough. A major UK make such as Crabtree may have sufficient capacity for 10mm cores, but you had better check the spec or ask the maker before buying. They will usually accept 2 x 4mm. If not, terminate the 10mm cable into a large switch

such as is used for a cooker or shower. 10mm cable is large and stiff and you will need a deep backbox woth plenty of room for the cores to curve gracefully into the terminals and gently bend as you push the switch into place.

An FCU has a fuse, you can put a 3A one in it. You will probably be able to get a 6A MCB for the CU. Are you competent to fit it?

if you want, you can run a 3A towel rail off a lighting circuit. It has very little power and will be pretty ineffective.

 

[AndyPRK]

I would use the 10mm for a socket in the loft, etc.

Maybe better to run the towel rail off another circuit

 

[Taylortwocities]

That towel rail will need RCD protection. Does the old shower circuit have such a thing?

 

[SUNRAY]

Doubt you'll find a 3 amp MCB

Why not?

 

[AndyPRK]

Not exactly common are they.

And expensive when any other value would do!

 

[aptsys]

May as well run the 10mm to a socket in the loft for general purpose use and then drop down to the radiator with an FCU.

 

[EFLImpudence]

I am sure the OP must be thoroughly confused. Let's start again.

Is there any reason I can't use an existing run of 10mm twin/Earth for an electric towel rail.

No. but you could just run it off the lighting circuit.

An electric shower has been removed but I'm thinking, rather than running a spur off the ring, I can just use the existing 10mm run

You can.

but change the MCB to a 3amp instead.

No need for that. Incidentally what rating is the present MCB?

Is there anything in the regulations to say that this shouldn't be done?

No.


Right, as you will need a junction box in the loft. this might as well be a socket, as already said.
Run a smaller cable - 2.5mm² to cover fault protection - from the socket down to the towel rail.
As you will need a junction box to connect the towel rail, this might as well be an FCU with a 3A fuse (even if not actually required).

All good and compliant.

 

[Risteard]

Socket-outlets are not designed to take 10mm^2 conductors, so terminating in one really isn't a satisfactory solution. I suspect BS 1363 also stipulates that they are to be protected with no greater than a 32A protective device (although Irish Standards ones permitted a 35A Diazed/Neozed fuse when they used to be commonplace).

 

[EFLImpudence]

Please tell us the difference in design specifications that would be required for10mm².

 

[JohnD]

Socket-outlets are not designed to take 10mm^2 conductors

https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=24909

 

[JohnW2]

Socket-outlets are not designed to take 10mm^2 conductors, so terminating in one really isn't a satisfactory solution.

Well, MK ones, and probably others, are 'designed to take' 3 x 4mm² or 2 x 6mm² conductors (12mm² total in both cases), so I would not have expected 1 x 10mm² to be either a problem or 'beyond the design'.

Kind Regards, John

 

[ban-all-sheds]

Or even larger.

3 x 4mm² conductors in a trefoil require a (round) terminal equivalent to 1 x 18.7mm²

 

[JohnW2]

Or even larger. 3 x 4mm² conductors in a trefoil require a (round) terminal equivalent to 1 x 18.7mm²

Indeed - although, in practice, they would squash a bit and therefore not as large an effective total CSA as you suggest.

However, no matter how arranged/distorted, 3 x 4mm² conductors are obviously never going to have less total CSA than 1 x 10mm² !