Rcd protecting new ring main

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davek

Hi all,
I have been to look at a job, in a unit who require extra socket in a office. It is one of those building that has been split into small units,
The supply is 3ph. Each unit is supplied from mains with separate meters and a 3pole isolation switch with bs88 fuse 63a.
the board is a merlin gerin isobar 4c. the breaker are c60hb. my thought where rcbo but I can only get a c rated 32a which using table b6 gives me 0.58 ohms the zs at supply to board is 0.18.any thought or suggestions.
thanks
Dave
 
Re: Rcd prottecting new ring main

Can you not spur off an existing socket, and install a rcd socket outlet?
 
Re: Rcd prottecting new ring main

I did not want to use existing as some of it looks quite old and shabby, don't think customer would go with the expense of 7 rcd sockets fitted the other thought I had was fit a small rcd c/u nect to the board and put in a 40a b type.
 
Re: Rcd prottecting new ring main

Your post never mentioned 7 new sockets mate,I'll think it over
 
Re: Rcd prottecting new ring main

first question is what's the design current of the new circuit. if it's office, then a lot of the load may be IT... low current but high integrity earthing.
 
Re: Rcd prottecting new ring main

Ok thanks sorry sometime you forget add these thing as was mainly thinking on the breaker there is about a 5 meter run to the office partion so cable length is a concern on r1+r2
 
Re: Rcd prottecting new ring main

as far as a I have been told just heater fan or some oil rad pc and printer just sort of wanted socket add all round for general use as far as I know
 
Re: Rcd prottecting new ring main

davek said:
Ok thanks sorry sometime you forget add these thing as was mainly thinking on the breaker there is about a 5 meter run to the office partion so cable length is a concern on r1+r2
Click to expand...

I'm pedantic Dave you mean R1+R2 surely, try ebay for a MG b type rcbo Ive just had a quick butchers and there seems plenty to chose from
 
so, say yout rfc circuit is 50m end-end. that will give you a R1+R2 of approx 0.25Ω. addthat to your 0.18Ω, gives a Zs for the circuit of 0.43Ω. well within the 0.58Ω you quoted for the RCBO.
 
Last edited:
hi pete
yes may have et one off net just ha a quick ring round must locals only ha c in some just sounds like it was something odd
 
Can you get 20amp type c or b? If it's a small office you could wire a couple of radials in 4mm which will give you plenty to play with
 
telectrix said:
so, say yout rfc circuit is 50m end-end. that will give you a R1+R2 of approx 0.25Ω. addthat to your 0.18Ω, gives a Zs for the circuit of 0.0.43Ω. well within the 0.58Ω you quoted for the RCBO.
Click to expand...

yes hope full, just didn't want be to near the limits, but may order a b type just found one on tlc cheaper than the c breaker I have so that may be the answer
 
The Schneider KQ range come in type B, simply buy one of these and remove the clip on attatchment and there you have a type B MCB that will fit this board.
 
just spotted an extra zero in my post. didn't realise my fingers stutter. must be the cold.edited now.
 
Schneider bought over merlin gerin so is essentially the same make. It's not a good idea to try to get another make to fit the db as its not to manufacturers instructions therefore any issues with it in the future it'll be your name on the sheet saying that's ok.
 
bigdavs83 said:
It's not a good idea to try to get another make to fit the db as its not to manufacturers instructions therefore any issues with it in the future it'll be your name on the sheet saying that's ok.
Click to expand...
Strewth not that old chestnut again, as long as the OCPD fits correctly there is no problem with this.

That rumour needs putting in the same place as cuttting off a plug top i validates the warranty.
 
it's still a get-out for the manufacturers in case of trouble. they can afford high powered lawyers. we can't.
 
Dillb said:
Strewth not that old chestnut again, as long as the OCPD fits correctly there is no problem with this.

That rumour needs putting in the same place as cuttting off a plug top i validates the warranty.
Click to expand...

i'd fail it straight away. It's not to manufacturers recommendations. If the manufacturer recommended that you don't do it a certain way and you do it that certain way then you are setting up for a big fall should it go wrong. Looks guff as well
 
bigdavs83 said:
i'd fail it straight away. It's not to manufacturers recommendations. If the manufacturer recommended that you don't do it a certain way and you do it that certain way then you are setting up for a big fall should it go wrong. Looks guff as well
Click to expand...

And if the MCB's/RCBO's are essentially manufactured in the same factory on the same production lines, on the same machines, only the manufacturers logo and part/model numbers etc, differ??

You'd be surprised just how many so-called manufacturers use 2nd party manufacturing company's to supply their own products and licence product production for 3rd party manufacturers.
 
I'm with Dillb on this...is it fit-for-purpose ? If yes fit it.

I don't invite all my friends (yes both of them) to look at my DB, so I don't care what it looks like as long as it is safe for my family and the wife can reach a tripped circuit with a stick :cheesy:

Its a recommendation ("this may invaladate the warrenty") not mandatory, its just another reason for them to try and weasel there way out with their shoddy product.... and don't get me started on fans and 3A fuses.
 
At the last NIC visit I was told that installing a different 'make' of breaker was a no no, even if it was the same breaker labelled differently...................I laughed.....then went outside and had a whistle.
Schneider IS Merlin.
 
bigdavs83 said:
i'd fail it straight away. It's not to manufacturers recommendations. If the manufacturer recommended that you don't do it a certain way and you do it that certain way then you are setting up for a big fall should it go wrong. Looks guff as well
Click to expand...

Care to explain what you would "fail" it on?
 
bigdavs83 said:
i'd fail it straight away. It's not to manufacturers recommendations. If the manufacturer recommended that you don't do it a certain way and you do it that certain way then you are setting up for a big fall should it go wrong. Looks guff as well
Click to expand...
LMAO, really, what a lot of tosh.
 
Dillb said:
Care to explain what you would "fail" it on?
Click to expand...
It is a different colour lol, absolutely identical otherwise and made in the factory on the same machine and inspected by the same person but slightly different in colour so it is now dangerous, oh and it is your name on the test sheet :smilielol5:
 
nissan recommend shell oil in their engines. i put castrol in mine. does that invalidate the warranty?
 
Re: Rcd prottecting new ring main

davek said:
was just sort of adding up 5 meters plus 7 drops averaging 4.5 mts per drop plus the 10 meter for run to room possibly 50 meters total cable for ring
Click to expand...
buy a copy of the "onsite guide"

they recommend max of 100m for 2.5 ring mate or 50m for a radial. more load or longer distance go for 4mm etc,
why is it a concern?


and why not use a b type rcbo?
 
I would it fail it because of the manufacturers recommendations! Not rocket science that. Now we all know that a hager breaker is not gonna blow up as soon as as it is fitted in any different type of db to which it can be fitted. Should it go pear shaped tho it's your door they are chapping. Anytime I see it any of the commercial dbs I come across I report as a fail. You've got a nice 76 way board and one breaker is completely different from the rest! Looks guff and has in the past failed insurance audits. During PIR tests our testing guys will always pick it up as non compliant.
 
But you cant fail a PIR anymore as they no longer exisist. Can you show me a copy of any MI thats shoes only OCPDs of a certain type can be fitted to a certain board and what the consequences will be if you dont?
 

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