Does electric shower require RCD?

[The Jeep]

Hi - I am planning to fit an electric shower in a flat. The fuse board is one of the old rewireable types, but can't be easily updated as the flat is wired in pyro (MIMS) cable, so there's absolutely no slack.

However, there is an unused way that I can wire into with 10mm2 T&E for the shower, which I will then protect with a suitable fuse. My question is: do I need to fit an RCD to the shower circuit (my feeling is that I don't, as it's fixed equipment, though the disconnection time has to be 0.4s). Is this correct?

 

[industryspark]

Dont qoute me on this but i dont think its actually a regulation that you must have RCD protection for a shower but the manufacturers i think strongly recommend it.

in my opinion though and most sparks i know an RCD is a must have for a shower circuit.

think about it, the things draggin 40 odd Amps whilst your stood a foot away from it wet thru.

i believe you can now by RCD shower boxes so you can come off your CU onto this RCD box and then out to your shower ( via the switch obviusly).

well worth the money if you ask me.

 

[JohnD]

BTW if you have an old rewirable fuse box, it is quite likely to be inadequate for an electric shower. Unless it says otherwise on the front, you can expect it to have a 60A main switch, and not to fit MCBs above 32A.

This is especially true if it is a brown Wylex, as the blocks for earth and neutral are undersized by today's standards.

You might do better with new tails, a 100A DP switch, henleys and a new CU with RCD for the shower. Before you know it, you will be thinking it would be better to have a complete new CU with RCBOs

 

[RF Lighting]

I agree with industryspark, it is not a regulation to RCD protect a shower but it is very good practice to do so.

You could fit an RCD in a seperate enclosure (fed from the existing board), henly the tails and fit a seperate shower CU, or get your old CU replaced.
I personally don't see why a board feeding MICCs is any more of a problem to replace that plenty of arkward mains changes I have done in the past.

If your board is old enough for rewireable fuses, is it capable of handling an additional 40A?

 

[RF Lighting]

RCBOs

Think I was a bit slow with my reply there.

 

[Spark123]

The only time an RCD must be fitted is when the manufacturer specifies it. It is advisory to fit one for the reasons Industryspark gives and most sparks go over and above the requirements and fit RCD protection to shower circuits as a matter of course.
The disconnection time for fixed equipment is normally 5s, in a fault condition in your bathroom you are heavily reliant on your supplementary equipotential bonding to keep you alive, if the risk can be removed more quickly then it can only be a good thing.

edit: OOPS, was industryspark not JohnD!!!

 

[JohnD]

I cannot claim the credit, it was industryspark who wisely said

"think about it, the things draggin 40 odd Amps whilst your stood a foot away from it wet thru. "


I just like RCBOs

 

[plugwash]

not that the current rating of the circuit has any significant impact on the shock risk, but i agree anything that your using wet and naked and is liable to be sprayed with water should be RCD protected.

 

[martin43]

Hi all

This issue cropped up in a recent post of mine. I read on a site, which I now cant find, that suggested that the 2001 amendment to the regs called for RCD protection on showers. Now I could well have misunderstood this and be wildly wrong, either way it's still a good idea.

Regards
Martin

 

[martin43]

Hi all

Found this http://www.tlc-direct.co.uk/Book/5.9.3.htm

which quotes thus

Protection by an RCD with a rating of 30 mA is required for fixed electrical equipment installed in a bathroom or in zone C of a swimming pool.

.

Seems pretty unequivocal, I presume a shower is fixed electrical equipment.

Regards
Martin

 

[Adam_151]

It only applies to some fixed electricial equipment, see page 59 of the OSG

I like many others wouldn't want a shower without RCD protection, and I rather hope that the next major revision of the regs changes this, but as it stands no RCD protection for showers is needed unless the shower company specifies it

 

[The Jeep]

Yes, it does seem from the regs that RCD protection is not required, but it's obviously a good idea.

The trouble with MIMS cable installations in the flats I'm working in is that there really is NO slack cable for the purpose of installing a modern CCU. I would have to use some kind of connectors to extend at least some of the cables - not a very desirable practice. In another flat, I ran completely new circuits as the pyro (MIMS) had previously been condemned, so there was no difficulty in installing a new split-load CCU with RCD protection for the shower and ring main circuits. Mind you, that was a LOT of work, as I had to chase most of the circuits into the walls!

Perhaps the solution is to use Henley blocks and take a separate feed off the mains (after the meter!) which can run to a small single-way RCD unit.

I'm also taking note of what has been said about drawing 40-odd amps from the existing old-fashioned fuse board. This may indeed be a no-no. Interestingly, the main protective fuse in these flats is located outside next to the lift shaft (behind a metal door, of course) and appears to be a HBC type rated, surprisingly, at 60A. It is my belief that this value of 60A is a conservative one and that a modern CCU with 100A main switch protection can be safely employed within the flat. I do realise that there is an issue with the correct protection for the MIMS incomer, though. This cable is buried in concrete, by the way, and therefore would appear to have good heat dissipation properties. And there is diversity to consider. Any further comments, guys?

 

[Adam_151]

Can't you put a new fuseboard in exactly the same place so the holes that the pyro pots gland off into don't actually change, and then crimp the cores inside the fuseboard that don't reach their fuseways as per normal with any fuseboard change?

What size is the pyro incommer? with a 60A fuse and pyro I'm guesisng it might be 10mm² ?

 

[The Jeep]

Thanks Adam. The thing is the pyro comes in at the top and there is only a short distance to the fuses. Most CUs that I've fitted have a greater distance from top to MCBs/neutral/earth bars. You suggest crimping on (presumably) extentions to the wires - is this acceptable practice?

When you say 10mm2 (OK, how do you get the little '2' character?), I presume you mean the x-sect area of each conductor. Don't think it's as much as 10, but I'll check tomorrow.

 

[Steve]

a quick note here. we had a BROWN 100A wylex board with a wooden back. how rare is that??? it also had a 40A MCB plugged in, furthest fromt he mainswitch, operating a electric 8.5 shower.