RCDs in 17th Edition

[ml1936]

17th Edition requires all circuits to be supplied via 30mA RCD if buried less than 50mm, correct?

What if the main incomer is a 100A 30mA RCD? Is this ok? Will it not cause dangerous situation if power fails due to fault? How is this interperuted in 17th Ed?

The new dual RCD CUs. Upstairs lights on with downstairs sockets and vice versa. But what if only 1 lighting circuit? Like in older/smaller houses? Would power (Sockets, Cooker, Shower, etc) on one side like on split load boards be ok, with lights on other RCD?

Please can someone give me their interperations???

 

[GaryMo]

17th Edition requires all circuits to be supplied via 30mA RCD if buried less than 50mm, correct?

You have to comply with any one of five options from 522.6.6 if cables are going to be concealed in walls or partitions at a depth of less than 50mm

(i) Cable with earthed metallic covering.....
(ii) Enclosed in earthed conduit.....
(iii) Enclosed in earthed trunking.....
(iv) mechanically protected against damage......
(v) Installed in safe zones.....

Now where 522.6.6 (above) applies and the installation is not intended to be under the supervision of a skilled or instructed person, a cable installed in accordance with 522.6.6(v) and not complying with 522.6.6 (i), (ii), (iii) or (iv) shall be provided with additional protection by means of an RCD.

What if the main incomer is a 100A 30mA RCD? Is this ok?

Doesn't comply.

The new dual RCD CUs. Upstairs lights on with downstairs sockets and vice versa. But what if only 1 lighting circuit? Like in older/smaller houses? Would power (Sockets, Cooker, Shower, etc) on one side like on split load boards be ok, with lights on other RCD?

In that situation I would probably use a high integrity board (assuming the client wouldn't pay for a board full of RCBO's) and put the lighting on an RCBO with sockets for up and down on RCD1 and RCD2 along with other circuits.

 

[ml1936]

ml1936 wrote:
What if the main incomer is a 100A 30mA RCD? Is this ok?


Doesn't comply.

Why dosnt it comply?

 

[Mike2007]

ml1936 wrote:
What if the main incomer is a 100A 30mA RCD? Is this ok?


Doesn't comply.

Why dosnt it comply?

I have asked some awkward questions on this site and was told to buy the regs, which I did! Now I read them and will ask if something does not make sense to me.
If you are in and out of CU's go and buy the 17th regs! Saves these guys having to dig deep into theirs all the time.

 

[GaryMo]

Regulation 314.1 - Every installation shall be divided into circuits as necessary to avoid danger and inconvenience in the event of a fault,
take account of danger that may arise from the failure of a single circuit such as a lighting circuit, reduce the possibility of unwanted
tripping of RCDs etc

I agree the installation would already be split into separate circuits but can you see how a single fault would isolate the whole installation?
It's not a good design is it?

 

[ml1936]

What code would this be on a pir then? 1 or 2? And why?

 

[pompeygit]

On my list a code 4