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Posted By Topic: RCD 2.6.2.4 (b) ii

texynz
Dec 12 2017 22:16

Ok. So whilst looking at stuff on a FB page, I have been alluded to the fact that should you have more than ONE final circuits you shall have two RCDS.

This for the main reason that shall the RCD trip it that lighting is not killed to the entire installing, or how it is put in the standards "minimise the impact of the operation of a single RCD"

Honestly I have seen many which have only followed the 3 breakers per RCD, and have installed some myself which have been inspected and never had it flagged.

So the logic is that for a "portable building/portacom" for example, you can have 1 40A-RCBO as you main switch/fault protection, then one breaker for GPO, and then another RCBO for lights. Just for the a small <10 square meter room...Just adds more $$$ to the bill and more wiring mess in the board.

Can they not just flag that rule and just say, RCBOS for everything, would make life alot easier to understand. I can say I have learnt something new, and noone in the past has flagged it as an issue which is the surprising part...
   

pluto
Dec 13 2017 07:12

texynz Dec 12 2017 22:16

Your comment 1 (Parts only)
Ok. So whilst looking at stuff on a FB page, I have been alluded to the fact that should you have more than ONE final circuits you shall have two RCDS.

My comment 2
You need to read the whole of 2.6 of 3000 to get the correct answer.

Your first paragraph should read

"If you have more than TWO LIGHTING final circuits you shall have two RCCB".

Your comment 2
This for the main reason that shall the RCD trip it that lighting is not killed to the entire installing, or how it is put in the standards "minimise the impact of the operation of a single RCD"

My comment 2
That is correct reasoning.

Your comment 3
So the logic is that for a "portable building/portacom" for example, you can have 1 40A-RCBO as you main switch/fault protection, then one breaker for GPO, and then another RCBO for lights. Just for the a small <10 square meter room...Just adds more $$$ to the bill and more wiring mess in the board.

My comment 3
Two possible arrangements are permitted
1. A 40 amp RCCB to supply up to 3 MCBs,(using the above example) one for lighting and one for GPOs.

2. Two RCBOs as the final sub circuit over current and earth leakage protection for each final sub circuit.

Your comment 4
Can they not just flag that rule and just say, RCBOS for everything, would make life alot easier to understand. I can say I have learnt something new, and noone in the past has flagged it as an issue which is the surprising part...

My comment 4
The wiring rules as currently written allow the use of RCBOs only if you choose that method of providing over current and earth leakage protection by a common protective device.

   

texynz
Dec 13 2017 08:30

Thanks Pluto I will relook at it again and find the Section which refers to lighting but those ozzie were adamant it was for more than one for any type of circuit
   

pluto
Dec 13 2017 08:34

The $$$ for the extra RCDs they could charge is clouding their thinking!
   

AlecK
Dec 13 2017 09:34

Pluto is correct that clause 2.6 should be read as a whole, however this aspect relates only to 2.6.2.4. It's in two parts.

Firstly, part (a) says if ther'e more than one RCD, and there's more than one lighting circuit, then must split the lighting circuits across the RCDs. Applies to all installations, and does NOT mean any extra RCDs.
For the portacabin, unlikely to be more than one lighting circuit. In fact unlikely to be more than one RCD either. So very unlikely to apply.
   

AlecK
Dec 13 2017 09:35

Secondly part (b) sets two additional requirements for residential installations:
(i) the 3-subcircuit rule; and
(ii) minimum 2 RCDs unless only one final subcircuit.
So unless your portacabin is residential, these won't apply either.

For a residential submain to small outbuilding, there's unlikely to be more than 3 subcircuits, so one RCD satisfies that bit.
At the bottom end, could be only 1 subcircuit, in which case still only one RCD req'd.
If two subcircuits arguably (b)(ii) calls for 2 RCDs. But i don't believe that argument holds up. The installation requires more minimum 2 RCDs, but the outbuilding on its submain is only part of the installation; and the clause only has to be complied with across the entire installations, not across sections of it.
   

Sarmajor
Dec 26 2017 19:18

"Honestly I have seen many which have only followed the 3 breakers per RCD, and have installed some myself which have been inspected and never had it flagged."

It is not the Inspectors responsibility to check this aspect of the job when "Inspecting" the High Risk aspectes of the installation.
It is the responsibility of the Electrician and the Certifier to ensure that the rules regarding things like this are followed.