Three Phase RCD & MCB Wiring?

Well if you need RCD protection on single phases independently of the two other phases then then yes 3 x RCD (RCCB)  i.e 1 per phase or better still each MCB to be an RCBO (an RCCB & MCB combined in one unit)  instead. If you have any actual 3 phase loads then you need a 3P+N RCD (RCCB) for that circuit only. Not for any single phase circuits.

Note By "Cost effective" the initial cost of One only RCD per phase then to all the MCBs on that phase will be the cheapest initial outlay. But RCBO on each circuit will mean only that one faulty circuit will trip an leave the others capable of running. A 4pole (3P +N) RCCB can not be used on single p[ole circuits as it will trip unless all three phases are drawing exactly the same currents

Dan


Ask a qualified and competent person to design this installation for you to meet the requirements of British Standard 7671 and any applicable standards and statutory requirements. This is not a job for an amateur to do.

No Ebee that is not correct, any load on any phase is satisfactory, if you think about it any drop in N current is reflected in the other phases. It is the sums of all of them together which causes the trip. It may be slightly difficult to see but remember the 3 phase are all 120 degrees apart so sums ar not quite so simple, including the N current which will probably be out of phase with all the live phases. The result is exactly the same as a single phase RCD, the lack of exact summation is what causes the trip.

What you draw is OK for  a system where 3 phase comes in, but all loads are single phase.   In effect you have drawn 3 single phase consumer units - and that is one  legitimate approach, if your loads are like that.

3 phase boards for 3 phase loads have a 3 pattern L1 L2 L3  bus bar so every tooth is only connected to the ones multiples of 3 places along.


. And just to catch you, L and N  (pitch of two) and 3 phase and neutral (pitch of 4 ) busbar is also manufactured but rarer.


an RCD for a 3 phase load must carry all the phases, and neutral if there is one, so that in normal use, it sees no net current.


I suggest you contact the helplines of  one of the makers of commercial consumer units (Hagar, Eaton etc) to advise you about what they make, as there are a lot of options, and it is very easy to specify the wrong thing, the advice is free, so long as you do not string them along..

Are the loads in your drawing correct, or just nice numbers ? Thinking diversity.

M.

Is this a re-hash of previous threads?


On the face of it, you simple use an RCBO for each circuit, but as JP says, this is a job for a skilled person.

John. Unfortunately I don't have the £4,800 that I have been quoted.  I'm looking to do most of the installation myself and get it fully checked and connected by qualified personnel. Cheers.

Dan, how do you propose to satisfy R. 16 of the EAWR 1989?

Dan, do you need to have RCD protection for the whole of each circuit? Or just near the ends? It might be better to get a quote to install three 3-phase RCCBs near the ends of your circuits.