On 24/10/2013 18:17, ARW wrote:
Bill wrote:
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?

Bill.

Whip off the front cover and take a photo of the inside of the CU. That
looks like the SB6000 and you cannot get single module RCBOs for that model.
And it would be cheaper to replace the CU considering Crabtrees prices.


And Denmans do good value Bundle deals.... you can get a 10 or 14 way
Curve CU with your choice of 10 RCBOs for around 100 quid plus vat.