Electrical work for new electric shower and jacuzzi

[Migue]

Am looking for a bit of advice on some electrical work I am doing in my bathroom. I am doing it mostly myself and am planning on putting in a new electric shower and jacuzzi bath (1700*700, not hottub!).

I have upgraded the existing electric feed for the shower to 10mm twin and earth because the shower I have bought is 10.8KW, and I will be putting in an rcd in the electric cupboard.

I was also planning on hooking up the jacuzzi to this feed too. Due to the rather large capacity of 10mm cable I was thinking of using an RCD as low as maybe 5 amps?, which I was probably going to put in under the bath itself (The rating of the jacuzzi is 4 amps).

At the electrical cupboard, assuming the voltage is 240 (or 230?) Thats around 45 amps and with the jacuzzi thats around 49 amps , so i am assuming I will have to use an rcd larger than 45 amps. I could make a point of never using the two together but would prob rather it didn't cut out if I did!

What is the next size above 45 amps (rcd rating) and does what I have mentioned above all seem above board?

Any advice greatly appreciated

Miguel

[Andy Wade]

It would be more conventional to feed the Jacuzzi from a nearby ring circuit (socket circuit) via a fused connection unit. Since this is notifiable work which you'll need to have inspected and tested, using unconventional arrangements might lead to difficulty.

Make absolutely sure you get the supplementary bonding done correctly, otherwise your work is likely to be failed.

Under the bath is not a good place for controls and switchgear which are supposed to be readily accessible. Such items need to be in zone 3, or beyond the zones or outside the bathroom.

Your 10.8 kW (at 240 V) shower needs a 45 A Type B _MCB_ (or a suitable fuse). There's no need for RCD protection unless the earth-fault-loop-impedance is too high, e.g. if you're on a TT-earthed installation.

If you're not sure of the difference between an MCB and an RCD, and if you really think that a 45 A MCB would trip when carrying 49 A, then you might want to think about getting an electrician in.

[meow2222]

If you're in a hurry, I'd have to agree. If you want to wire up the shower and jacuzzi yourself, you'll need to take the time to read up on the various requirements first.

As already indicated, one important question is which type of earth system have you got.

NT

[Miguel]

To be honest, im not entirely sure whether it is a TT earth system. I have been 'tinkering' with electronics for years. I have an idea of some of the regulations and if i'm not sure I ask :) Think i was using the term RCD too loosely too.

I'm pretty sure it is not an TT earthed sytem however. There are no RCD's in use anywhere else at the moment and I have mcb's in my electrical cupboard. Is there any easy way to tell for sure?

The only ring mains I could tap power from (without lots of effort) is from a socket on the other side of the wall, although I am pretty sure it is a spur, and was not entirely sure it should be used. Hence, I was wondering about the implications of using the shower feed.

Few thoughts...

1. Am I better off just forgetting about using the idea of the shower feed?

1. If I do use the spur, the manufacturer of the jacuzzzi and many other sources recommend using an RCD. Realistically, the RCD could only go under the bath or behind my fridge freezer (neither that convenient if it does trip). Is there any way I can put it under the bath safely? What about using IP66 sockets which claim to be safe with the cover closed or open? Also, I am assuming I would use a rather small RCD, say around 30mA?

2. On the other side of the room to where the bath is, I have a ring mains feed which used to be used to power an old bathroom heater. My plan is to drop this cable down and use it to power the heated flooring, which also recommends use of an RCD. With a bit of effort i could prob get this cable round the room to the bath and power the jacuzzi. The heated flooring is 300w, so would I have to use a larger RCD?

1. I take it another possiblity is to put an RCD in at the electrical cupboard, although this would obviously have to have a higher rating, increasing the risk?

Thanks again , Miguel

[David Hansen]

On 20 Jun 2006 16:55:31 -0700 someone who may be "Miguel" wrote this:-

You do the same thing in this posting.

Is the socket useful? If it is not, why not replace it?

Probably. The necessary components would be bulky.

Only if it is accessible only with a tool, such as unscrewing a bath panel. However, I would argue that this is in itself dangerous, as the panel will then be left off.

A lower rating would probably be better.

Is this on the ring, or another spur? However, this sounds like a better option to power both. Alternatively a dedicated circuit may be easy to run alongside the shower cable. That would get the RCD in the electrical cupboard.

You are confusing two different sorts of protective device (though they are sometimes combined in one gadget). You need to understand the difference before going any further.

Would it? Until you can work that out for yourself you should leave wiring alone. This is not electronics.

[Andy Wade]

You're contradicting yourself there.

Unlikely to be TT then (I hope). Have a look near the supply intake position and see what the main earthing conductor is connected to.

If you don't particularly need that socket you could replace it with a fused connection unit, or an RCD spur like

you need an RCD there.

To do this you'd need to tee off from the input side of the shower isolator to a fused connection unit in 10 mm^2 cable, or provide a design calculation to show that a smaller cable is adequately protected by the 50 A MCB that you'd need for the circuit.

The RCD could go on a wall as an RCD spur (see above) or could go at the origin of the circuit (ring or shower, whichever you use) near the consumer unit. (Use a 2-module DIN rail RCD in a separate 2-module plastic housing.)

No, because of the mutually exclusive requirements that the bath panel must require a tool to remove it (otherwise your RCD would be in a forbidden zone) and that switchgear must be readily accessible.

No, a 30 mA RCD would be fine. Are you sure that your UFH system is suitable for use under a bathroom (with particular reference to Reg.

601-09-04)?

Yes, as I mentioned above, and a 30 mA RCD is still what's needed. Why do you think "this would obviously have to have a higher rating"?

[Miguel]

OK, here goes, I will try and reply to andy and wade's messages at the same time...

I have an electrician coming in to do some work in my kitchen today, I will ask him if he knows what type of earthing system I have. I live in a flat, making it difficult to trace where the earth comes from. I could get an electrician in to do the bathroom, but being a skint student (electrical & mechanical engineering), and already having spent a load of money on the suite etc, i wanted to see if it was possible to do it myself (got a good deal on jacuzzi before you ask)

Both of you seem to disagree slightly on the size of RCD I would use. According to other sites, 30mA makes it pretty unlikely that I would ever be seriously hurt.

With reference to putting the RCD in the electrical cupboard, this is something that a number of websites claim you can do. I suppose 30mA would maybe be fine here also(?) because the equation L-N=0 still stands irrespective of the load.

My heated flooring is from warmup.co.uk. which I got recommended by a few people (good or bad I have bought it now :) ) . They do claim on their website, after a bit of hunting that it can be used in bathrooms.

"The RCD could go on a wall as an RCD spur (see above) or could go at the origin of the circuit (ring or shower, whichever you use) near the consumer unit".

When you say near the consumer unit, does that mean it can't go inside the CU? What about if I use a rcbo?

The spur does get used at the moment for my fridge. The easiest option sounds like using this. If I cut a new hole to house the RCD spur, is there any reason why the fridge and jacuzzi cannot be connected to this?

Thanks again for your patience

miguel

[Miguel]

One more question. Part of my bathroom, behind the bath, has been partitioned off at some point to house the hot and cold water tanks. There are cupboard doors to gain access. What do the regulations say as far as putting electrics in here?

Miguel

[Owain]

30mA provides reasonable protection from electrocution in most circumstances. However if you are actually immersing yourself in water in a jacuzzi bath you may want to use a higher standard of protection eg 10mA.

Why do you think that the placement or the load makes any difference to the trip rating of the RCD you require?

An unfused spur from a ring can supply *one* socket (either single or double) or one FCU.

Owain

[Miguel]

"irrespective of the load" - I don't think the load does make any difference, but was just wondering what size I would use, not going to go down this route anyway.

Ok, this certainly seems like the easiest way to do it.

Thanks for your help, Miguel

[meow2222]

if youre really determined to do it yoursef, at least put it on an rcd. But dont kid yourself this makes it safe, it doesnt. Death rates from electrocution have not been significantly cut by fitting rcds.

Putting the whole house on one rcd is not a good idea. Putting a fridge freezer on an rcd supplying wet equipment is also not a good idea. You can do as you choose of course, but I dont recommend it.

NT

[David Hansen]

On 21 Jun 2006 13:02:35 -0700 someone who may be [e-mail] wrote this:-

That doesn't surprise me. Do you have a source for this? If you do I can file it away with information about other "safety" initiatives.