80A 100mA RCD in Domestic TT installation?

L

leascliffe

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Hi,

I am starting out as a domestic installer and would really like some of your advice please??

I went to preview a job today to replace some pendant light fittings. The customer said the CU was replaced in 2010 together with a new earth rod being a TT supply. The overhead lines come into the distributor's fuse, tails out to the meter and just one pair of tails from the meter into an MK insulated C/U. The C/U consists of a 80A 100mA Time delayed RCD as main switch and 10 MCB's. There does not appear to be any other C/U at the property so I was wondering why the original installer went for a time delayed 100mA RCD?

I'm concerned there is no 30mA protection and believe the 100mA time delayed RCD should be swapped for a standard 30mA. Wondered if any of you have experienced the same and agree or disagree? Thanks!
 
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GLENNSPARK said:
get the 100mA s type upfront....30mA RCDS for your finals....
is there a garage here by any chance?
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Thank you all for your replies so far, much appreciated! Glennspark, yes there is a garage but the customer said there's nothing in there, but definitely worth a look me thinks! :)

My house is a TT supply and I replaced the C/U here for my first Elecsa Assessment, the board is an insulated dual rcd board, just a 100A main switch upfront (no time delayed RCD) and the assessor did not pick up about any missing 100mA time delayed RCD, do the regs say we have to put the 100mA upfront as well as the 30mA to the finals? Will have a read this evening....
 
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individual rcbos IMO is the way to do it with a 100 MA s type as the incommer, but it isn't the only way, Glenn and Trev are right though and the dual rcd boards with 30 ma rcds is a cheap way but still acceptable, you don't need the 100ma s type, but do need 30 ma
 
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leascliffe said:
Thank you all for your replies so far, much appreciated! Glennspark, yes there is a garage but the customer said there's nothing in there, but definitely worth a look me thinks! :)

My house is a TT supply and I replaced the C/U here for my first Elecsa Assessment, the board is an insulated dual rcd board, just a 100A main switch upfront (no time delayed RCD) and the assessor did not pick up about any missing 100mA time delayed RCD, do the regs say we have to put the 100mA upfront as well as the 30mA to the finals? Will have a read this evening....
Click to expand...
if its a plastic C/U then keep the 100mA s type ....they may need this in future for the garage feed should they wish to go down the route of a supply in there....
this is what i was thinking ahead about at #4
 
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leascliffe said:
Hi,

I am starting out as a domestic installer and would really like some of your advice please??

I went to preview a job today to replace some pendant light fittings. The customer said the CU was replaced in 2010 together with a new earth rod being a TT supply. The overhead lines come into the distributor's fuse, tails out to the meter and just one pair of tails from the meter into an MK insulated C/U. The C/U consists of a 80A 100mA Time delayed RCD as main switch and 10 MCB's. There does not appear to be any other C/U at the property so I was wondering why the original installer went for a time delayed 100mA RCD?

I'm concerned there is no 30mA protection and believe the 100mA time delayed RCD should be swapped for a standard 30mA. Wondered if any of you have experienced the same and agree or disagree? Thanks!
Click to expand...

Are you sure they are simply MCB's and not RCBO's.?....(apologies if this is insulting your intelligence but you have stated you are just starting out)
 
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wirepuller said:
Are you sure they are simply MCB's and not RCBO's.?....(apologies if this is insulting your intelligence but you have stated you are just starting out)
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Don't worry, I'm used to being insulted :wink_smile: Sure, they are all MCB's. I think the customer will only be prepared to swap the 100mA for a 30mA at the moment, there's no room to have the 100mA upfront in another small enclosure. I like the idea of keeping the 100mA as it is but replacing the MCB's for RCBO's, just not sure the customer will like the price tag...assuming the MK Sentry boards are big enough to take RCBO's (all 12 of them)

Thanks for all your advice, I'll let you know the outcome
 
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Murdoch said:
Not essential on a plastic CU.
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I'm not quite following your logic here. Why do you think a metal CU requires an ''essential'' up front S type RCD, but a plastic CU doesn't??
The S type RCD is as far as i'm concerned, there to provide the much needed extra protection on a TT installation, rather than relying on a single RCD devices that are frankly not known for their operational reliability!!

As far as the OP situation is concerned, he should have both, either in the form of a dual 30mA RCD, or via RCBO's!! As it stands at the moment, the single S type 100mA RCD CU, doesn't comply with either the present regulations, or the regulations in force at the time of installation (2010)!!
 
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Engineer54 said:
I'm not quite following your logic here. Why do you think a metal CU requires an ''essential'' up front S type RCD, but a plastic CU doesn't??
The S type RCD is as far as i'm concerned, there to provide the much needed extra protection on a TT installation, rather than relying on a single RCD devices that are frankly not known for their operational reliability!!

As far as the OP situation is concerned, he should have both, either in the form of a dual 30mA RCD, or via RCBO's!! As it stands at the moment, the single S type 100mA RCD CU, doesn't comply with either the present regulations, or the regulations in force at the time of installation (2010)!!
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Thanks Engineer54, my thoughts about the original installation are the same as yours, their company name is on a BIG sticker on the front of the C/U, the customer is trying to let the house and has been chasing the company for a copy of the original EIC, but the bloke hasn't replied...
 
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leascliffe said:
The customer has a Building Regs Compliance Cert but not an EIC and has been chasing one ever since. NAPIT told her they don't keep a copy of it, so will try the LABC, cheers
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The LABC wont have a copy of the EIC either.....when you notify a job, you dont send them a copy of the EIC, you just give them the Number you assign to the EIC. Well at least thats what you do with Elecsa.
 
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Jay Sparks said:
The LABC wont have a copy of the EIC either.....when you notify a job, you dont send them a copy of the EIC, you just give them the Number you assign to the EIC. Well at least thats what you do with Elecsa.
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So the only complete official copy of the certificate, is the one issued to the customer?? That sounds totally crazy to me!!

So what happens when and if say an electrician emigrated, as it sounds to me the only actual copy of any cert, is held by the electrician/company that conducted the work and completed a certificate. So where's the checks and balances?? How does anyone check anything, when something goes belly up, as far as i can see it would be an easy task to falsify a copy of any cert issued....
 
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Engineer54 said:
So the only complete official copy of the certificate, is the one issued to the customer?? That sounds totally crazy to me!!

So what happens when and if say an electrician emigrated, as it sounds to me the only actual copy of any cert, is held by the electrician/company that conducted the work and completed a certificate. So where's the checks and balances?? How does anyone check anything, when something goes belly up, as far as i can see it would be an easy task to falsify a copy of any cert issued....
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I Completely agree!!! When I enter the details of the install on the Elecsa website, they only ask for the EIC number!! So your right, the only copy(s) are held by the Electrician and customer (if one is even supplied)lol. The only time SOME certs are checked is when you have your annual assessment.....and the assessor just asks to see cert No. xxxxx!! There is no policing at all but we all ready know this whole idea is a big pile of poo!!!lol

I must state that this is the way Elecsa do it...not sure if the others do it the same way??
 
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I too am registered with Elecsa, I've just phoned them for advice and also NAPIT who the original installer is registered with. They both have the same complaints procedure laid down by the Government. The customer has to give the original installer opportunity to put it right (A.N. Other contractor cannot correct the original work at this stage). If the contractor does not reply, then a complaint must be sent in writing to the certification body, who will investigate and decide the outcome, in this case it seems the contractor 'could' be struck off, meaning they would struggle to re-register with any other certification body.

The customer is emigrating at the end of this month and intending to let their house, don't think this will be possible while the complaint is ongoing and only 100mA protection in place, oh dear!...
 
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leascliffe said:
I too am registered with Elecsa, I've just phoned them for advice and also NAPIT who the original installer is registered with. They both have the same complaints procedure laid down by the Government. The customer has to give the original installer opportunity to put it right (A.N. Other contractor cannot correct the original work at this stage). If the contractor does not reply, then a complaint must be sent in writing to the certification body, who will investigate and decide the outcome, in this case it seems the contractor 'could' be struck off, meaning they would struggle to re-register with any other certification body.

The customer is emigrating at the end of this month and intending to let their house, don't think this will be possible while the complaint is ongoing and only 100mA protection in place, oh dear!...
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The problem there is, the guy prob won't even care if he can register again coz he will just get a third party to do it, or just not bother notifying!!!! Its a bloody crock of poo!!!




Registration my ---!!!lol
 
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So how long to you have to allow, for the original installer to put things right?? And how long to completion, after the official written complaint has been registered. It makes you wonder, just how much the safety of an installation or to it's occupants, matters to these scam providers? They beat the safety drum hard enough when it suits them, but when it comes to safety costing THEM money, it then becomes another story altogether!!

As for the original electrician/contractor being struck off, i doubt that very much, and even if he did, would have no trouble signing up with one of the others. I doubt very much that they have any common dialogue between them...
 
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Engineer54 said:
So how long to you have to allow, for the original installer to put things right?? And how long to completion, after the official written complaint has been registered. It makes you wonder, just how much the safety of an installation or to it's occupants, matters to these scam providers? They beat the safety drum hard enough when it suits them, but when it comes to safety costing THEM money, it then becomes another story altogether!!

As for the original electrician/contractor being struck off, i doubt that very much, and even if he did, would have no trouble signing up with one of the others. I doubt very much that they have any common dialogue between them...
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That's what the chap from NAPIT told me....

He said to allow the contractor 15 days to reply to your complaint in writing, if you do not receive a reply, then the customer issues a written complaint to the certification body and they will investigate, anyone's guess how long it could then take to get it resolved. It's probably less stressful for the customer to forget the complaints procedure and just pay another contractor to put it right, the trouble is they'll be out of pocket for 12 RCBO's (being the least disruptive replacement), what are your thoughts on cost for this? I think cheapest MK Sentry RCBO's are about £24each plus certification etc...
 
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leascliffe said:
That's what the chap from NAPIT told me....

He said to allow the contractor 15 days to reply to your complaint in writing, if you do not receive a reply, then the customer issues a written complaint to the certification body and they will investigate, anyone's guess how long it could then take to get it resolved. It's probably less stressful for the customer to forget the complaints procedure and just pay another contractor to put it right, the trouble is they'll be out of pocket for 12 RCBO's (being the least disruptive replacement), what are your thoughts on cost for this? I think cheapest MK Sentry RCBO's are about £24each plus certification etc...
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No idea on the cost side of things, not being UK resident for a number of years now. I'm sure others here will know and give advice on that side of things...

What was the the rods Ra value on this installation?? Is the earth rod a standard 5/8'' extendable, or one of those short thin twigs they have the cheek to call an earth rod?? A photo or two would be interesting to see!! lol!!
 
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Thanks :). I did check the Ra and surprise, surprise it's 130ohm and I don't think the 'new' rod is extendable either, probably not even 5/8" - I'll be going back to break the news so will try to post a pic or two
 
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In the past on TT installations.......light circuits with no cpc......100ma time delayed RCD's were used as a main switch / isolator.
But then usually 30ma RCD for skts etc giving discrimination.
 
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driverman said:
In the past on TT installations.......light circuits with no cpc......100ma time delayed RCD's were used as a main switch / isolator.
But then usually 30ma RCD for skts etc giving discrimination.
Click to expand...

Not in 2010, TT installations have required overall 30mA protection for some years now, sockets on TT systems, have required 30mA protection even longer.
 
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JASON said:
I always thought that the CU had to be all insulated to avoid the 100ma rcd, as its only there to protect the tails.
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Seems the 100mA is normally used either upfront followed by 30mA RCD's in a C/U, or if it's in a distribution board powering another C/U with RCBO's elsewhere so that there is discrimination between them. All insulated on TT to avoid the live tails unlikely touching a metal case (before any protection from RCD's)
 
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leascliffe said:
Seems the 100mA is normally used either upfront followed by 30mA RCD's in a C/U, or if it's in a distribution board powering another C/U with RCBO's elsewhere so that there is discrimination between them. All insulated on TT to avoid the live tails unlikely touching a metal case (before any protection from RCD's)
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Yes metal enclosure, not for a plastic one.
 
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JASON said:
I always thought that the CU had to be all insulated to avoid the 100ma rcd, as its only there to protect the tails.
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I know what your saying, and agree in principle with your above comment. But how many follow the complete recommendations on TT based CU's, like all MCB's/RCBO's being of the DP variety, very few i'd wager...lol!!
Tails into metal-clad CU's used on a TT system, can be more than adequately protected entering the CU by use of a suitable gland or even a suitable grommet/blind grommet. Hell, the tails are insulated and sheathed to start with...

What an upfront 100/300mA S type will achieve on a TT system, is provide an extra/added level of protection to single RCD's covering multiple circuits. The alternative is totally relying on those single RCD's for your earth fault protection. And we all know that RCD's are not the most reliable of protective devices, be they from the high end manufactures, or from budget manufactures...
 
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80A 100mA RCD in Domestic TT installation?
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