Faulty MCBs??

[mullin]

Just wondering if there is a finite live time for an MCB. Reason I'm asking is that since Tueday I've had two which appear to have failed, both on different ring circuits, both 20 Amp.
I had to turn both breakers off on Tuesday as I had to remove some sockets from the wall in order to put the wifes loverly new wallpaper behind them. So off they went, papering done, went to switch them back on again one of them (which powers the sockets in the utility room and hallway) came back on no problem at all, the other (which powers the kitchen sockets) wouldn't latch.
Unplugged everything in the kitchen - still wouldn't latch. Powered down everything and removed the MCB and tried it again still wouldn't latch (think I'm correct in assuming they don't need power to latch on, it's just a plain and simple 20 MCB). So off to the nearest electrical emporium and got a new one, fitted it, turned on no problems since.
Just got a phone call from the wife (I'm stuck on the nightshift this week) to say that now the other MCB (hall and utility room) has tripped and won't reset or latch. Got her to unplug everything in these rooms which I have been assured was done and the breaker still won't latch back on.

So is it just a case of the MCBs needing replacing, maybe something internal to them has given up the ghost since I touched them on Tuesday - specially since the one I replaced on Tuesday wouldn't stay on even after being removed from the CU or could it be something else?? Had no problems with the MCB's before this, the sockets I removed were in the hall which are on the MCB which gave up tonight so I'm assuming the sockets themselves are ok as they have been on for the last two days, I guess there is the possibility that something has come loose in them, maybe I didn't tighten them up properly on Tuesday but that'll have to wait till the morning before I check it.

Not too sure as to the age of them, we've been in the house for about 2 years, I'd say the place is maybe 10 years old so somewhere around that sort of age.

 

[mullin]

No takers for this one then eh!!

Okay, so changed out the MCB and everything is hunky dory again now, this one had gone the same as the other - the breaker was not latching on.

Maybe I'll reword the question...............is there a period of time after which it is recommended that MCB's are changed/replaced?? In a similar vein how about the house wiring itself?? Is it recommended to get a rewire done after a period of time (say 20 years+) or is it just a case of leave it alone until there is a problem.........

 

[uselessFCUK]

The mcb ratings are lower than the typical 30/32amp per ringmain.

Check the current loading of the ringmains under normal load.

It may be that the ringmains are pulling in excess of 20amps, the mcb doesn't neccessarily trip in a partial overload condition but the heat generation likely weakens the internal gubbins (mechanism).

If the ringmain cables are >=2.5sq.mm then B32amp mcb upgrade may be the solution. Obviously check with a qualified electrician or competent person.

 

[securespark]

****

This poster lives in Ireland (yes?) so wiring codes differ from UK regs. Circuit ratings are different.

 

[uselessFCUK]

Paddy and Murphy have always been different.

What's there ringmain setup?

I'm sure a 2.5sq.mm ringmain in Eire is not a completely different science, is it?

Please enlighten me.

 

[mullin]

Oops, my bad!! should have posted this in the non uk electrics one......

The ring main cable is indeed 2.5mm, but the breakers are 20amps, as securespark said i guess the regs are different over here. As I did my apprenticeship in the UK I too was expecting 32amp breakers for the ring main.

There's 3 rings mains, one for the kitchen sockets, one for the living room and one bedroom and the other does the hall, utility room and 2 remaining bedrooms (it's a bungalow) and all are run off 20 amp breakers.

Off the top of my head the CU contains the main fuse/switch feeding into a 63amp RCD (or is that RCCD).....3x20amp breakers for the ring, one 32amp for the cooker/hob/extractor, one 40amp for the shower, one 40amp which supplies another CU in the garage, 3 either 15 or 5amp for the lighting - I'll take a look when i get home in the morning and confirm this but i think that is whats there.

The wiring was checked by the ESB (company the supplies the leccy over here) when we were buying the place and all is in order, well it was 2 years ago.

Another thing I found a bit odd was that there is no twin and earth cable used over here, well not in any of the houses I've lived in anyways - all the wiring is done in single core cabling........easier to work with i suppose but must be a real pain to be routing that many single cores.

 

[mullin]

just incase anyone does answer............i won't be reading the forums till wednesday so if i don't reply for a few days doesn't mean i've disappeared or anything!!

Only have broadband access in work............one of the "joys" of living out in the middle of nowhere!! They've actually just installed broadband in the nearest town to me but as that is almost 10 miles away it'll probably be a few more years before it gets out to me!!

 

[plugwash]

from the fact that two of the same rating in the same CU failed so close together i would imagine it was a poor batch when they were made.