"Bill" wrote in message
...
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.


Photos please if you could be so kind

--
Adam