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

Migue wrote:

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).

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.

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!

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.

Any advice greatly appreciated

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.

--
Andy

Andy Wade wrote:

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.

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

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?

2. 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?

3. 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?

4. 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

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

Think i was using the term RCD too loosely too.

You do the same thing in this posting.

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.

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

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

Probably. The necessary components would be bulky.

Is there any way I can put it under the bath safely?

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.

Also, I am assuming I would use a rather small RCD, say around 30mA?

A lower rating would probably be better.

3. 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.

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.

The heated flooring is 300w, so would I have to use a larger RCD?

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.

4. 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,

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



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Miguel wrote:

To be honest, im not entirely sure whether it is a TT earth system.
[...]
I'm pretty sure it is not an TT earthed sytem however.

You're contradicting yourself there.

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?

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.

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.

If you don't particularly need that socket you could replace it with a
fused connection unit, or an RCD spur like
http://www.tlc-direct.co.uk/Products/BRH92.html
if you need an RCD there.

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?

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.

2. 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).

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.)

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?

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.

Also, I am assuming I would use a rather small RCD, say around 30mA?

Yes.

3. 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?

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)?

4. 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?

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"?

--
Andy

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

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

Miguel wrote:
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

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

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

Death rates from
electrocution have not been significantly cut by fitting rcds.

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.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54