clarification of cu upgrade on TT installation

[Stever_777]

Hi guys, after flat bashing for years, I'm now on my own and seem to only be working on TT installations. Can someone just clear this up for me please?When installing a new cu in a TT installation, do I need a 100mA time delayed main switch or can I just put a normal main switch in and have a split 30mA board.Steve

 

[Electro-tech]

Main Switch and RCBO's on every circuit, makes fault finding easy rather than multi circuits on one RCD.

 

[malcolmsanford]

Main Switch and RCBO's on every circuit, makes fault finding easy rather than multi circuits on one RCD.

Would you use double pole or single pole RCBO's for that

 

[IQ Electrical]

Would you use double pole or single pole RCBO's for that

Lol, I know where this is leading...

 

[malcolmsanford]

Lol, I know where this is leading...

Good morning young man or afternoon is it

 

[sparc]

Aargh!

Where is it leading??? You can't leave us hanging like this. I've never heard of double and single pole RCBOs - and now I'm thinking ***t did I install the right one last week!!

It's a just a joke, right?

 

[IQ Electrical]

The reg's call for isolation on all live conductors on a TT system but as pointed out in Guidance Note 5, a double pole main switch is acceptable (4-pole on 3-phase & neutral supplies).

 

[malcolmsanford]

Because of the nature of a TT system and the instability of a reliable earth, N-E fauts can sometimes not be cleared. The use of double pole protection devices should be used and though the regs fall short on this IMO I always would fit a double pole RCD, which was done as an upfront ELCB and then RCD.

This is what was always done pre RCBO days and I think that the IET have not moved with the advent of single pole RCBO's when using them on TT systems .

Which is why I asked if you are fitting a main double pole switch you will conform to Reg 537.1.2, but if only single pole RCBOs are fitted, I would consider that less than safe.

 

[Stever_777]

This particular board in question has only 4 circuits, so was thinking a 60A DP main switch then all 4 circuits on a 60A 30mA RCD????

 

[nickblake]

you wouldnd need both id go for an 80amp RCD main switch which is double pole no need for the main switch then dont forget the 63/80/100 RCD is not an overload device but an isolator/RCD the current rating on them is what they can handle

 

[Stever_777]

you wouldnd need both id go for an 80amp RCD main switch which is double pole no need for the main switch then dont forget the 63/80/100 RCD is not an overload device but an isolator/RCD the current rating on them is what they can handle

I understand that they provide no overload mate, so if I understand, RCD main then the 4 circuits....done and dusted?

 

[malcolmsanford]

As it is just the 4 circuits then division of the installation is not really achievable unless you start rewiring the place, so yes as nick suggested a 80amp 30mA RCD as your main switch so double pole and then 4 MCBs

 

[nickblake]

Thanks for filling in my missed bits malc nodded off lol

 

[malcolmsanford]

Thanks for filling in my missed bits malc nodded off lol

snooze .......you loose

 

[Electro-tech]

Aargh!

Where is it leading??? You can't leave us hanging like this. I've never heard of double and single pole RCBOs - and now I'm thinking ***t did I install the right one last week!!

It's a just a joke, right?[/QUOTE


Techna 30mA Single module 2 pole RCBO types B and C


Cheers Malcolm...for your input !

 

[JamesBrownLive]

Aargh!

Where is it leading??? You can't leave us hanging like this. I've never heard of double and single pole RCBOs - and now I'm thinking ***t did I install the right one last week!!

It's a just a joke, right?

Techna 30mA Single module 2 pole RCBO types B and C


Cheers Malcolm...for your input !

They seem quite cheap, is that brand any good??