wiring rcbo in dual rcd cu

[IRB]

I'm fitting a rcbo in a dual rcd cu for the smokes alarms, just wondering do you wire the neutral wire into the main switch? Wouldn't it keep tripping the rcd if I wired into the neutral bar?

 

[topquark]

Yes, it would trip if you used one of the neutral bars. If you want dual RCD and RCBOs then you're better off using a three neutral bar CU.

 

[IRB]

Is there no way of doing it in a cu with 2 neutral bars then as the customer has bought and fitted the cu?

 

[brucelee]

why dont you just connect the smokes to a existing lighting circuit instead
otherwise you are going to have to make the ccu a 3 way split

 

[Deleted member 9648]

It's pointless putting an RCBO onto a busbar already fed through an RCD,as a fault will trip both........if there are no ways not fed through an RCD just wire the smokes to a frequently used lighting circuit mcb.The smokes will also require a separate means of isolation,this can be a labelled key switch along side the DB.

 

[Guest123]

you're better off using a three neutral bar CU.

Thats called a high integrity CU.

 

[IRB]

I'm thought I read somewhere that the smoke alarms need their own circuit if the lighting circuits are on a rcd? is this right?

 

[topquark]

Is there no way of doing it in a cu with 2 neutral bars then as the customer has bought and fitted the cu?

If you did away with one of the RCD's then you could do it but you'd be left to replace the previously protected ways with RCBO's ... a bit pricey.

How many RCBO's are being fitted and what's the total loading?

 

[IRB]

Only 1 rcbo to feed 4 smokes

 

[Deleted member 19807]

putting the smokes on a frequently used lighting circuit means that if the mcb or rcd trip it will be noticed straight away and reset. I don't see any problem with this setup

 

[topquark]

Yep, page 66 in the OSG suggests that hifly ... sure I remembered reading that separate circuits were prefered if rcd protected but damned if I can find it now :-(

 

[IRB]

I can't remember where I read it either.

 

[topquark]

If you did away with one of the RCD's then you could do it but you'd be left to replace the previously protected ways with RCBO's ... a bit pricey.

How many RCBO's are being fitted and what's the total loading?

If it's only the one RCBO then you *could* wire the neutral to the output side of the main switch but how will you ensure it's securely held? (assuming that you use the busbar for the live (you'll now have 3 bits of busbar, not two)).

 

[Guest123]

Yep, page 66 in the OSG suggests that hifly ... sure I remembered reading that separate circuits were prefered if rcd protected but damned if I can find it now :-(

Electricians guide to the building regs mentions this. It's also in Approved Document B1.

 

[Des 56]

Yep, page 66 in the OSG suggests that hifly ... sure I remembered reading that separate circuits were prefered if rcd protected but damned if I can find it now :-(

i think you have that the wrong way round

Look at page 66 of the on site guide
note where rcd there is advantage using local lighting circuit


I discussed this issue with accordfire in another thread

http://www.electriciansforums.net/i...s-con-unit-question-17th-ed-2.html#post191298