RCD's (needed or not)

[downnout]

Hi, Just changed a mains board in a factory (3ph, 36 way) Put the power circuits on RCB'Os and the lighting circuits on MCB's. The wiring is either singles in a 3x2" trunking or using SWA tied onto tray. Am i correct in thinking that the lighting circuits do not have to be on RCD's??

 

[Spudnik]

You are indeed, unless any part of those circuits has cables buried in the walls.

 

[downnout]

I thought i was but some D*&k at work reckons everything has to be RCD protected. Does that apply to the SWA's?? I would say no because of the mechanical protection of the armourings.


Cheers for the prompt reply

 

[snowiespark]

I thought i was but some D*&k at work reckons everything has to be RCD protected. Does that apply to the SWA's?? I would say no because of the mechanical protection of the armourings.


Cheers for the prompt reply

i agree SWA even if in a wall wont need RCD protection as regs say , "cables in a wall must be (i think 50mm or more deep) or protected by a earthed metalic sheathing , so i would say that describies SWA......

 

[Cj24]

what determines if u should use an rcd or rcbo, does it depend on how it is wired etc cables buried in walls or conduit etc? because i might sound stupid but an rcd does not protect against short circuit but an mcb does well surely you want to be protected against short circuit dont u and if u overload circuit from wat i been told the rcd wont trip either, basically wat i been told is that rcd protects against just earth leakage so if someone was to touch live conductor

 

[Spudnik]

The MCB will protect against O/L and S/C with the RCD providing earth leakage.

An RCBO is the two combined.

 

[JUD]

Cj24....I think you're getting a bit confused about how CUs are set up.

It's not a case of weather you should use an MCB OR an RCD, you use them both, or alternatively you can use RCBOs in which case the RCD is not required as the RCBOs provide their own earth leakage protection.

The RCD protects multiple circuits. The RCD feeds the MCBs through a busbar (like a main switch does) so the RCD protects against earth leakage and the MCBs protects the cables from damage due to overload and short-circuit fault currents.

Hope that helps

 

[Cj24]

I get it cheers so if it is not an rcd'd board and u but u need to rcd one of the circuits is that wen u apply an rcbo, sorry if soundin thick just not gettin head round it, sure it will just click in a min

 

[caddy]

If its a commercial or industrial installation and under the supervision of a skilled / instructed person the the only things that really need to be on RCD's RCBO's would be socket outlets intended for general use.

Socket outlets intended for use for dedicated equipment IE Computers dont need to be. Circuits buried in walls dont specifically need blanket RCD protection. There is a big difference between what you can and cant do between Domestic and commercial / industrial units usually becuse of the "unless under the supervision of a skilled or instructed person" We do lots of work for commercial / industrial clients who employ maintanance staff. They are counted as skilled / instructed.

 

[JUD]

I get it cheers so if it is not an rcd'd board and u but u need to rcd one of the circuits is that wen u apply an rcbo, sorry if soundin thick just not gettin head round it, sure it will just click in a min

Correct