Wirlpool Bath wiring, some advice needed

[Jeff]

Hi all,

I am completely renovating our bathroom. I've come to installing our whirpool bath and reading the info sheet that comes with it, it asks that the pump is connected to the mains via a 30ms RCD and a maximum rating of 16A. I am thinking of using this:-

has a 16A MCB which I presume I can use for the bath pump. I also need to supply a lighted mirror in the bathroom and was thinking that the 6A MCB could be used for that. Will the unit I'm thinking of be ok?. It will be located in the laundry area adjacent to the bathrooom, not in the bathroom itself.

Also, the info sheet calls for the bath framework to be earth bonded, no problem, there is a 10mm Earth wire already in place but not used previously as the pipework is all plastic. I will also be installing a towel radiator using the existing pipes from the old radiator which didn't seem to be bonded at all. Once I have earthed the bath framework, should I also connect to the radiator pipework too?

Any help appreciated.

[David Hansen]

On Sun, 12 Nov 2006 18:22:26 +0000 someone who may be Jeff wrote this:-

Sounds like it.

It could be.

Probably. What will you be feeding it from?

Does your existing consumer unit have a spare way which could be used to feed the pump? Could you run a spur from an existing ring main? Both would be fed via an RCD.

Presumably you have installed a new radiator to provide heating of the bathroom? Many towel radiators don't provide much heating.

Have you thought of fitting an electric element to the towel rail for summer use, or feeding the towel rail from the hot water circuits so it can be activated in summer?

Yes. It doesn't cost much in time or money to do, compared to the alternative of checking whether it is necessary to do.

[Jeff]

Sorry for the tardy reply David, I've been too busy with the farm for internetting :-)

A feed from the CU which was installed by our electrician when we installed central heating. It was originally intended to use it to supply a dual source heated towel rail but I was thinking of hijacking it for the bath supply.

Our existing CU has one free way left but I am not sure that the isolator switch has and RCD hence my thinking the box I have bought would provide the protection necessary IF the CU is not protected by RCD. If the CU _is_ protected by RCD, should I buy a new RCD for my remote box of a lower ma value so it acts first?

The CU is an MK 12 way but there is no indication on the outside that it is protectd by RCD, will I need to open it up to check? It's probably 10-12 years old.

Yes, it is quite a large bathroom and I'll be putting another proper radiator on the opposite wall.

Yes, I have bought a 400w element from screwfix which they recommend for the towel rail (also from screwfix).

Ok, will do, I was just not sure whether earthing the rads would cause a problem after reading the DIY FAQ (which I encourage all readers of this group to peruse).

Many thanks for your advice , it is very much appreciated.

[David Hansen]

On Sun, 19 Nov 2006 10:08:02 +0000 someone who may be Jeff wrote this:-

If it has a test button then it undoubtedly has an RCD, which will probably have something like 30mA written on it. The question is whether any RCD covers every protective device, or just some of them.

Entirely logical.

The best way to try and differentiate between RCDs is to make one of them time-delayed, but this has implications for the rest of the building. RCDs with a lower rating are available, but may not reliably discriminate with one of a higher rating, especially if the ratings are relatively close.

As well as the above see if it is a split unit, which will have a main switch and an RCD, usually part of the way along the MCBs.

No need to bond radiators themselves, provided that they are fed by metal pipes that will have a reliable metal to metal contact with the radiator and the pipes themselves are bonded.

A towel rail with an electric element is different, because the towel rail is an item of electrical equipment. The supplementary bonding can either go to the towel rail itself or it can just go to the point where the flex from the towel rail is connected to the fixed wiring. The latter assumes that the protective conductor (earth wire) in the flex is short and can be relied upon.