Dual RCD's

[gerry.slater65@]

At College,haven't covered much yet about dual RCD's
What is the advantage of using two Rcd's over one.
What circuits would be on each section of the CU?
Also I have an old re wirable type CU and am thinking of changing it(with more knowledge).
I have a split load board with one Rcd would this be suitable for my terraced house,would it comply with the Regs?

Sorry,so many questions,so little time.

Any help with some or all of the answers would be greatly appreciated

cheers Gerry

 

[assured elec]

The 17th Edition requires most if not all circuits in domestic premises to be RCD-protected. There have been a number of suggestions as to how the consumer unit may best be configured to comply with the Regulations, the most common being a main switch with

RCBOs​

protecting each individual circuit. However, another suggestion favours a main switch with two

RCDs​

protecting separate DIN rails. If careful consideration is given as to what each bar will control in the way of upstairs and downstairs lighting and power circuits, will this configuration comply?
NDA2
Yes, as long as the division of final circuits between the RCDs is carefully considered so as to minimize the consequences of unwanted tripping. Separate RCD protection is not necessarily required for each circuit of an installation but, in order to minimize the likelihood and consequences of tripping, a single (‘front end’) RCD should not be used to protect all the circuits.

What it means is if you have 1 RCD protecting all circuits and one of the circuits develops a fault , this will trip the RCD and cut power to all circuits , which is what they are trying to avoid .... if you split the circuits over 2 RCDS if you have a fault on one of the rcd the other should not trip , meaning the you still have 50% of your circuits working .... which means you don't have total black out..... Hope this make sense , as it does in my mind

 

[Spudnik]

RCD's are ONE way of protecting cables buried less than 50mm from the surface of a wall/partition.


However, there are now requirements to RCD protect all circuits in a bathroom, all socket outlets etc.

So, Dual RCD boards are a cheaper then loading a CU with RCBO's, some of which can cost up to £30 each.

If you have a look in the OSG or the BRB it lists all the other options to avoid them, circuit permitting, Eg use of earthed steel conduit, surface wired etc.

So, in answer to one of your questions, no, a standard split load board will not meet current regs, unless you load the unprotected side with RCBO's.