RCD Board

Jim_Wilson · 4 Dec 2010

How can I tell if I have an RCD board ?

I have a Crabtree with 6 x MCB (SB6000) and a main switch witch has test button and quotes "100ma trip"

holmslaw · 4 Dec 2010

ericmark · 4 Dec 2010

That is an RCD however RCD's come in many flavours and we have as common sizes 10ma, 30ma, 100ma, 300ma and 500ma. Approx 3 times size of each other. The 300ma is a special as it is the size stipulated for fire protection and 30ma is a special as stipulated as largest that will protect personal.

The 100ma you have was common pre 2008 and was used for TT supplies normally feed from overhead wires where the earth rod was not good enough to ensure an earth leakage would open the overload device. (Fuse or MCB) It does not offer the protection required for use in bathrooms as where an electric shower is used there would be another one for shower. The same applies to sockets that could be used outside.

Since 2008 the requirement for RCD's has changed and today one would fit two 30ma RCD's instead of the 100ma you have. Also the 100ma often has a delay so does not stop you from being damaged by getting a shock.

Do remember even a 30ma at 40ms does not stop you getting a shock. It only prevents in most cases being damaged by the shock received.

So now I must ask why do you want to know? In most cases we would not change to 30ma just to comply with latest regulations but it could cause problems if you want to add on to what you already have. I think the new regs due out next year are going to reduce the requirements where adding onto an existing system. But as it stands any extra sockets would need RCD protection to the lower 30ma limit.

tonyelectric · 4 Dec 2010

Yes you have a 100mA RCD as said by others, this is not up to current spec but as the regs are not retrospective it can stand, however don't be tempted to rush in and change it for a 30mA because:-

A) Thats notifyable, either via an approved spark or yourself to LBC (costs abot £100 if you DIY)

B) It's very common to find that there may be a little niggling N-E fault floating around your system insufficient to be picked up on a 100mA but will trip a 30mA, a professional electrician would run a few rudimentary checks using their test equipment (which a DIYer is unlikely to have as it's very expensive) to make sure this is not going to ba an issue, and if it is locate and correct.

I see you are asking about a shed connection on another post, this will need a 30mA RCD, but that could be a separate entity to your existing board or a 30mA RCBo (a combined RCD/MCB in your existing board if space/design permits)

Your questions suggest you don't have much knowledge with regards to electrics, so I would really reccomend consulting a pro.

securespark · 4 Dec 2010

ericmark said:
RCD's come in many flavours

You've tasted them???

tonyelectric · 4 Dec 2010

I was assuming that the shed was not too far away!!, but if a long run, agreed V drop comes into play - but again another reason to get someone competant in to survey (or tell us the distance for more accurate info)

Another reason not to try and DIY that RCD change

you will either have to do it with live tails (dodgy, especially without the right PPE) or pull the cutout, which would be illegal and can be dangerous if you don't know what you are doing.

Incidently does anyone know what happened to the blue seal scheme here in the SEC area - It used to be the case that NICEIC contractors (only) could pull the cut out and re-seal with blue plastic seals that were numbered and supplied by the SEC depot to contractors, last time I went to get some was about a year back, but as far as I know a kick up by the regulators above SEC has ended that good, if a little unjust on other schemes contractors system.

Wontdothatagain · 4 Dec 2010

tonyelectric said:
Incidently does anyone know what happened to the blue seal scheme here in the SEC area - It used to be the case that NICEIC contractors (only) could pull the cut out and re-seal with blue plastic seals that were numbered and supplied by the SEC depot to contractors, last time I went to get some was about a year back, but as far as I know a kick up by the regulators above SEC has ended that good, if a little unjust on other schemes contractors system.

MOCOPA suceded in getting it stopped, they argued that only suitably trained persons should be pulling the fuse and just because you were a member of a compertent person scheme did not mean you were compertent to pull a fuse. The DNO's were also going to start training schemes for compertent persons to pull fuses and MOCOPA also got that stopped and they will only offer the course to persons working under the MOCOPA umbrella

Jim_Wilson · 4 Dec 2010

The shed is 6m away.

The reason I was asking is if the CU has an RCD, do I also need to fit an RCD socket in the shed ?

Tonyelectric,

I do have a reasonably knowledge, I just did not express myself fully on the other post.

tonyelectric · 4 Dec 2010

Thats a shame, I remember last time I went to the New Forest depot the foreman mentioned the courses, but as you say it all got stopped.

SEC seemed to have got the balance right, with people they knew were competant they let you do a bit more, saving both parties time, until about the same time they would also let you do PME conversion as long as you requested it in advance, they would check the grid plan - you did the work and that was that - I remember really getting moaned at by an SEC engineer who came out to do a PME on a TT for me "you can do that yourself, just ring the bloody office, why did you call me out etc etc.."! good old days c 12 months ago!!

tonyelectric · 4 Dec 2010

Hi Jim

Did'nt mean to offend, just didn't want anyone blowing themselves up.

I would RCD protect at the house end, that way you protect the cable, especially as you will have a non armoured bit, dont fit an RCD at the shed too or you will get both tripping in harmony.

As its going to be a plug and socket affair you are in effect making a fancy extension lead, why not use an RCD plug at the house end?

Wontdothatagain · 4 Dec 2010

I know the fuse pulling sarga will go on and on until it it writen down and published by all the DNO's but the long and short of it that it is not ilegal to pull a fuse. IF IT GOES WRONG, the DNO will have your pants down faster than George Michale in a public toilet and after putting the fuse back you have to have a means of sealing the fuse correctly.

As you say, it was great getting the seals from the S&S but now you can get the seals and wires off Ebay.

It needs the industry as a whole to loby the likes of MOCOPA and the DNO's for it to change.

Adam_151 · 4 Dec 2010

Wontdothatagain said:
MOCOPA suceded in getting it stopped, they argued that only suitably trained persons should be pulling the fuse and just because you were a member of a compertent person scheme did not mean you were compertent to pull a fuse.

... as opposed to a meter fixer who has been one on a one day meter fixing course who gets the polarity right about 50% of the time if he's really luckily

Wontdothatagain · 4 Dec 2010

...as opposed to a meter fixer who has been one on a one day meter fixing course who gets the polarity right about 50% of the time if he's really luckily

A bit of an unfair comment but not sure if you mean it with the wink at the end.

The company that i work for subcontract to a metering firm, installing smart meters and so we have all been on the course (it was more than 1 day) and are allowed to pull the fuse and have been issued sealing pliers to seal the meter and the fuse's.

It is a great way of keeping us all employed when things slow down and another way of getting leads for more work.

Click to expand...

mfarrow · 4 Dec 2010

tonyelectric said:
I would RCD protect at the house end, that way you protect the cable, especially as you will have a non armoured bit

I would say the opposite - there's no need to protect the cable - you're just running it out from a plug socket, out through a wall and then SWA to the shed, right?

If so then there's no need really for RCD on it. The fuse is sufficient to protect the cable, and if the armour is properly earthed then it'll do likewise for you (not that it's easy to put a spade through SWA mind).

RCD at the socket will also prevent you having to tramp back to the house in muddy boots to reset it.

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RCD Board

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