In message , Bill
writes
Hi all, especially the knowledgeable electricians on here.

What are your thoughts on me replacing all of the MCBs in my CU with
RCBOs? At present I have 14 MCBs all protected by one 30mA RCD main
switch. Over the last few years I've had tripping problems from a
trapped L to E fault in a metal clad light unit, it too 10 years before
this became a problem! Water blowing into an extractor fan, water in
an outside light and the big issue of too many switch mode PSUs in the
house. While some of the genuine faults were a pain and time
consuming to locate the SMPSUs are something I have to live with and
they are taking my overall leakage too near the 30mA limit on the CU.

This has been brought to a head by a few trips this evening, no one
circuit being the culprit, leave any 2 or 3 MCBs off and it is happy,
just not happy with all on, I'm assuming something is leaking a bit
more than normal and has taken the main RCD to it's limit. I've left
one circuit off that has a number of SMPSUs on it and so far all is
stable again.

Yes I will turn everything off and check the trip current of the1 RCD
in case it has become overly sensitive, but NOT tonight!

So my thought was to replace the main switch/RCD with a simple switch
and then all of the MCBs with RCBOs, everything will be protected and
in the event of a real problem I don't lose the whole darn house, just
the one errant circuit.

So is it a practical idea? I think so, but would welcome any thoughts,
good or bad about doing it. I know the 17th edition suggests a split
load CU, but that would still leave me with a 50/50% split and a gamble
as to what worked and what didn't.

Yes I am competent to do it, just nervous that I may have missed a
fundamental flaw in the idea.

If it matters the CU is a Crabtree Starbreaker with a single 80A
switch/30mA RCD and 14 MCBs and a DIN mount bell transformer.



Apart from the cost, am I crazy?


I think that I can now answer that. I am crazy.

OK I'm not the best electrician in the world and I certainly don't do it
for a living, but from start to finish, well almost finished, took nigh
on 12 hours today.
Fitting 2 boxes with DIN mount terminals above and below the CU to
accommodate cables coming from above and below. Identifying each cable,
disconnecting each from the CU and then removing the CU from the wall
and striping it and rebuilding. Then connecting each circuit to the DIN
mount terminals and then jumpering these into the CU.

I even tested out the rings for continuity and all was OK, something I
had been meaning to do for a while.

A plus point is having a separately fed annexe, some where to run a lead
light from and more importantly, somewhere to boil the kettle!

I did look at just fitting the RCBOs into the CU and not bothering with
the terminals, HA!! not a chance, it is cramped even with just one
single L&N from each RCBO Never again!

Any way, thanks to all for their advice a while back, it was much
appreciated.


--
Bill