bathroom rcds

[Sam]

Hello,

I'm waiting for my on-site guide to arrive from Amazon. In the meantime, please could you tell me the rules regarding RCDs and bathrooms?

Does the bathroom have to have its own RCD'ed CU or can it come off the RCD in the main CU?

How is a bathroom normally wired? I appreciate electric showers have their own, thick, radial, but I am thinking of a 400W towel heater. Would you run a dedicated radial to this or could it be run as an RCD'ed spur off the upstair's ring main?

TIA Sam

[Tim S]

Sam coughed up some electrons that declared:

I don't have my books to hand, so I'm going to check this later, for the

17th - but, tentatively:

From memory, *all* circuits in a bathroom need RCD protection. This includes the mains supply to any SELV transformers that supply anything in the bathroom (even if the transformer is somewhere else, lighting, hard wired appliances like washing machines and boilers (though there may be a caveat if say the boiler is in a locked cupboard).

Also, no sockets within 3m of zone 1.

No real restriction on where the RCDs (or RCBOs) are.

Towel rail off a fused spur is OK, provided there is an RCD protecting the circuit.

Cheers

Tim

[Ian_m]

In my last house had an electric towel rail spured off ring via an RCD located on the landing. Did modify adding a time clock to reduce electric bill as without a timer didn't dry the towels too well as the thermostat tended to turn it off when the central heating was on (leaving damp towels), so you turned in up and it never turned off.

[David Hansen]

On Fri, 07 Nov 2008 12:07:58 GMT someone who may be Sam wrote this:-

One of the objectives of a ring final circuit is to allow a variety of devices to be connected to it, thus achieving economy of materials without disconnection of the circuit due to overloading. Heavy and steady loads should not be connected directly to one, such as large heaters, but a 400W towel rail is the sort of small load which is ideal to connect to the ring.

[John Rumm]

The same RCD protection as elsewhere is fine, so long as it is by a How is a bathroom normally wired? I appreciate electric showers have

There was a point where it appeared that bathrooms were going to pose a special requirement wrt to RCD protection, in that they needed it for

*all* circuits entering the room including lighting etc. However another amendment to what finally became the 17th edition introduced a requirement for additional protection of buried cables. That to all intents and purposes makes it simpler to provide RCD protection (suitably partitioned to maintain discrimination) for all circuits in the house anyway - so the bathroom gets a free ride.

A 400W load is fine on a ring circuit.

[The Natural Philosopher]

No, I am fairly sure that none of that is needed. 13A sockets are (almost)not allowed, and the rest is either well out of reach, or double insulated.

Yup. Which n most bathrooms means 'no sockets'

Ah, in that case you may be right. Everything else normally runs of a lighting circuit,

[Sam]

I'm puzzled by the remarks about the thermostat. Did you have a thermostat in the bathroom or was there a thermostat in the element? Mine is just a plain element; the thermostatic ones seem to be £80 plus, but I thought they would switch off at scalding temperatures, rather than room temperatures?

Did you have an external thermostat; if so are they allowed in zone 3? I suppose a wireless one would be allowed but does it agree with the humidity?

I did wonder about using a CH controller to act as a time switch; it would also give a one hour boost option that you would not get with a plain time switch. A one hour boost would be useful because like you say, you don't have to remember to turn them off. However I wasn't sure that a CH controller would be sufficiently rated? I know 400W is barely a couple of amps, but is there a spike when it switches on or off?

[Sam]

I wouldn't have asked had it been anywhere else, but I wasn't sure whether being the bathroom it required its own circuit.

Thanks for all the replies.

[Sam]

That's interesting. I was going to ask what if the socket falls within zone 3 but also within 3m metres of zone 1 but I went online to search for a diagram of the zones to check whether this would be possible and I have learned that there is no zone three anymore. Why has this been lost? Is it only sockets that are forbidden because I will obviously need a FCU to connect the towel rail to. I wasn't sure how waterproof the fuse was.

Thanks for all the replies. It is reassuring to know it can be connected to the RCD in the consumer unit. This has the disadvantage of taking the other circuits out of there is a problem, but hopefully false alarms on the bathroom will be non-existent.

Thanks again.

[Sam]

I forgot to ask: presumably there was no RCD at the CU if you had an RCD'ed spur? I once used one of those plug-in RCD things, not realising that it was plugged into an RCD'd ring. When I pressed the test button on the unit it caused both the RCD in the plug-in part to trip but also that in the CU, so I presume there is no advantage to chaining RCDs; it's not as thought the first one trips before the second in the chain.

Thanks again.

[Tim S]

The Natural Philosopher coughed up some electrons that declared:

I'm afraid that it *is* the case that *all* circuits in a location containing a bath or or shower. Double insulated and out of reach aren't relevant under the 17th

Now I've got me books to hand:

Regulation 701.411.3.3:

"Additional protection shall be provided for all circuits of the location, by use of one or more RCDs having the characteristics specified in Regulation 415.1.1"

415.1.1: 30mA sensitivity,

[Tim S]

Sam coughed up some electrons that declared:

That's correct.

The only common (domestic) case where you do chain RCDs is on a TT (earth rod) installation.

There, the usual solution is a 100mA (or 300mA) Type S (time delayed) RCD protecting everything, and the usual 30mA RCDs everywhere else.

The time delay engineered into the Type S is specifically set so that a normal RCD will open the circuit first.

Cheers

Tim

[Tim S]

Sam coughed up some electrons that declared:

That's right.

Don;t know - probably something to do with harmonising the regs with european conterparts (though the german VDE100 regs *do* allow a shuko socket with suitable RCD protection in a bathroom).

FCU is fine. The theory is more to do with some daft sod pluging their hair dryer in and being able to sit in the bath using it (3m is based on the longest length of flex likely to be fitted to an appliance).

As far as siting, use common sense and certainly avoid areas likely to e hit by direct spray.

One solution sometimes used is to put only a flex connector plate in the bathroom, then put the fused-switch behind it on the other side of the wall.

Cheers

Tim

[John Rumm]

I think it is because zone 3 as a concept (ordinary appliances allowed, but must be protected by a > Is it only sockets that are forbidden because I will obviously

Lets hope they were not planning to sit in the bath and clean the grout with their Fein multimaster then (4m ish lead) ;-)

The general requirement that accessories should be chosen so as to be appropriate for the situation still applies. So as you said, use common sense and you will be fine.

[The Natural Philosopher]

When di thise regs come in? fairly sure not mentioned in 2000 regs..

[David Hansen]

On Sat, 08 Nov 2008 07:42:54 +0000 someone who may be The Natural Philosopher wrote this:-

1/7/08, from when all installations must comply with the 17th Edition.

There was an amendment to the 16th Edition in April 2000 to do with bathrooms, but the 16th Edition dates back to 1991 (though with various amendments after that date).

[David Hansen]

On Fri, 07 Nov 2008 22:11:04 GMT someone who may be Sam wrote this:-

It depends on the voltage and distance from bath/shower. Hopefully your book has arrived now and you can read the details.

People using the bathroom are unlikely to try and do something with the fuse, which is tucked away in the connection unit. Fused connection units pose no greater risk than a cord outlet. What is more likely to cause danger is operating a switch, which is why there are regulations about where they can be placed.

Obviously a fused connection unit should not be placed in or directly above a bath/shower (other than at high level, but many bathrooms don't have the height), but other places are generally fine.

There are several ways to wire a towel rail in a bathroom. A non- exhaustive list is:

1) switched fused connection unit. The switch needs to be far enough from the bath/shower. 2) switch outside and fused connection unit inside. 3) switched fused connection unit outside and cord outlet inside. 4) pull cord switch inside and fused connection unit by rail.

Neon indicators are useful on some/all equipment.

[Tim S]

The Natural Philosopher coughed up some electrons that declared:

Early this year, mandatory for new circuits 1/7/2008 - officially the crossover period of using either 16th or 17th has passed.

Ironically, it took the IET until September to get the updated On Site guide out.

Cheers

Tim

[Owain]

insert *new*

Owain

[David Hansen]

On Sat, 08 Nov 2008 10:52:17 +0000 someone who may be Owain wrote this:-

Indeed. My mistake.