17th Edition Board on a TT system

[Zeespark]

Main switch then RCBO's all the way bud, reduces nuisance tripping but is more expensive.

AndyGuiness Drink

 

[Andy™]

yet doesnt comply... and there is new thread with the same question

 

[batty]

I have just extended my house and my old memera 2000 box has insufficient ways for the new circuits. Not only that its a TT system with a 30ma RCD as main switch and protection on a solid board. (Fitted by the local authority before I bought the house). Consequently the whole system goes down if I get a nuisance trip. I intend to replace the CSU with an MK sentry 19 way box. It has a 100amp main switch and a I intend to fit an 80amp double pole RCD. I wish to protect a couple of circuits with RCBO's, if I get a nuisance trip on an RCBO is it also likely to trip the RCD, or can I put the RCBO's on the unprotected side of the RCD on a TT system.

If consumer unit is wired corrrectly only one Rcd or Rcbo should trip if you have a fault.

Batty

 

[msb2003]

There is a reg that says that any fault protective devices should be double pole, so single pole RCBO's are a no no

I'm struggling with this bit! Where does it say this? Fault protection is against indirect contact and ADS can be provided by MCB's, fuses or RCD's.

What about this, Reg. 314.2 states- Separate circuits shall be provided for parts of the installation which need to be separately controlled, in such a way that those circuits are not affected by the failure of other circuits, and due account shall be taken of the consequences of the operation of any single protective device.

Any board with only 2 RCD's will have numerous MCB's/circuits connected to each and a fault on one circuit will have an effect on the rest on the same RCD. Stricktly speaking then, every circuit requiring RCD protection should be on an RCBO!

 

[Adrian]

I'm struggling with this bit! Where does it say this? Fault protection is against indirect contact and ADS can be provided by MCB's, fuses or RCD's.What about this, Reg. 314.2 states- Separate circuits shall be provided for parts of the installation which need to be separately controlled, in such a way that those circuits are not affected by the failure of other circuits, and due account shall be taken of the consequences of the operation of any single protective device.

Any board with only 2 RCD's will have numerous MCB's/circuits connected to each and a fault on one circuit will have an effect on the rest on the same RCD. Strictly speaking then, every circuit requiring RCD protection should be on an RCBO!

Correct

but because of the cost to do rcbo 's the regs allowed us to use 2 rcd's

Its when it suits with them

I can see this all changing in the next ammendments

they make use bond water and gas, they are no longer metallic services that are providing an external potential so why bond them

 

[batty]

Correct

but because of the cost to do rcbo 's the regs allowed us to use 2 rcd's

Its when it suits with them

I can see this all changing in the next ammendments

they make use bond water and gas, they are no longer metallic services that are providing an external potential so why bond them

Adrian

Try connecting a live cable to a metal sink a house with a tiled floor thats a bit wet and touch the sink and see what sort of shock you get from that.

Batty