Rcd and TT

[johnnyjb]

Hi just wondering bout a senario that i could be up against soon.

Ive to upgrade a fuse board to a new one(needs a rewire but that ll be later)
the system is TT i think after the MSF can i just use an rcd 30ma on the sockets or does the whole installation need to be protected by a certain type or size Rcd due to it being TT

Any help appreciated

 

[ricicle]

Why are you attempting this work if you don't even know the basics?

 

[johnnyjb]

Forget it
Is this a forum to get help and learn or is it a place to be ridiculed i dont want or need help from someone that looks down their nose so quickly

 

[ColJack]

it's nothing like that, don't be offended so quickly..

I know sod all about cars so if a mechanic told me that I have no idea how to do an engine change then I wouldn't mind..

what you are doing is dangerous, can lead to fire or even death if not done properly...

I've never done work in a TT installation and so I wouldn't undertake one on my own.. even though I do have the knowledge to do one..

you're supposed to have a 100mA rcd as the main switch on TT installs..

 

[RF Lighting]

you're supposed to have a 100mA rcd as the main switch on TT installs..

100mA Type S RCD is the norm

 

[johnnyjb]

I understand what your saying but i know nothing bout cars either but i could pretend and talk rubbish to you but that wouldnt make me right in what im sayin
Im an apprentice ,if i was never to inquire or try things i didnt fully understand i still be bearing back T+E for sockets till im 45. im competent to a degree

Anyway thanks for your reply,nice simple answer that i was looking for

 

[DESL]

Johnny

If you'd said you were an apprentice in the first place I think you may have got a more technical answer.

Thing is this a DIY site and sometimes it becomes obvious by the nature of the questions that there is a lack knowledge.

If you're following an apprenticeship never be frightened to ask questions.

I see your location is Ireland if it's Eire I'm not sure whether regs are same I know they're modeled on BS7671 but there may be subtle differences.

 

[johnnyjb]

DESL thanks,i have a small idea of Bs 7671 im doing a city + guilds night course,our regs are similiar but different,some times its handy to know the different ways as this can lead to better workmanship

 

[DESL]

If you haven't got a copy of the Irish equivalent of the on site guide get one.

I don't know whether Eire is updating their regs as UKis going over to 17th Ed 1/7/08

 

[RF Lighting]

I do some work in Ireland (back there in 2 weeks ), and from what I've seen your distribution boards are nothing at all like British ones.

Also I've seen DP RCBOs feeding radial socket circuits, no rings AFAIK.

Wiring styles are pretty similar, but there are some differences.

 

[very_pointy_ears]

you're supposed to have a 100mA rcd as the main switch on TT installs..

100mA Type S RCD is the norm

What does Type S mean, speciflcally? (sorry if this is a hijeck, it's not meant to be).

 

[johnnyjb]

RF was that domestic or what,we are taught on site and in college and ive never put a socket an rcbo,only showers, i didnt quite understand the ring bit if your saying we dont use ring main circuits we do.Im mostly domestic by the way

 

[RF Lighting]

S type means it is a time delayed RCD, which provides discrimination from the 30mA RCD protecting sockets etc.


Jonny, all my work in Ireland is commercial (in theatres).

It was a brand new theatre in Dublin where I saw the DP RCBOs for the sockets

 

[johnnyjb]

RF isnt a rcbo just an rcd and mcb combined but it sounds silly having to buy an rcbo for every circuit

 

[ColJack]

yes, those are the things..

the usefullness of them is that you can RCD protect only a few circuits that need it..

you maybe only need 2 rcd protected circuits in a standard house at the moment, 1 for the shower, 1 for the downstairs sockets..

but a split load 12 way board will be 6 RCD protected and 6 not..

if you have a fault on one of the 6 circuits protected by the RCD, you lose all 6 circuits.. so fridges go off if you put the kitchen ring on the RCD side, shower, alarm clock if you put the upstairs ring on as well...

with RCBO's only the circuit with the fault goes out..