Mcb trip problem

[shed69]

Had an odd one today.... Help and thoughts appreciated....

Done a consumer unit change about 3-4 weeks ago, Hager CU....

Ring circuit does bedrooms, and living room - that's it.... Guy has an office set up in one room and has a lot of stuff up there but only computers etc... Bedrooms nothing more than a tv,phone charger etc, living room tv couple of lamps, nothing major... Not had a problem before but also appreciates it isn't anything from my work.... It was on a B32 on old CU and never tripped... Guy good as gold and not making it up!!

The mcb is a B32, all tested out fine. Changed it to see if faulty but happened again....

Any ideas???

Obviously it's on rcd but it's only the mcb tripping suggesting overload....

 

[lineman]

Any appliances recently bought?

 

[Monkeyboy]

Are you saying the B32 trips BUT not the RCD, suggesting overload and not fault condition. Also the ring circuit has no heavy load connected?

 

[NozSpark]

Adjacent MCBs getting hot and forcing this one into a thermal trip????

Possibly:C

 

[shed69]

Are you saying the B32 trips BUT not the RCD, suggesting overload and not fault condition. Also the ring circuit has no heavy load connected?

Yes, exactly that.....

 

[steptoe]

between shower and cooker maybe?

 

[shed69]

Adjacent MCBs getting hot and forcing this one into a thermal trip????Possibly:C

Like ya thinking...... I'll check that, going back tomorrow...

But wouldn't the hot one go too?????

 

[steptoe]

Adjacent MCBs getting hot and forcing this one into a thermal trip????

^^

 

[Evans Electric]

What can it be I ask myself ?

MCB will trip when :-

An overload occurs.

A short circuit occurs.

There is something with a high start up current.

He does arc welding in bedroom.

Its not connected properly to the fingers and gets hot so the thermal part is not happy.

The breakers either side are working near their thermal limit and heating your breaker up.

Its one of those Electrium breakers thats about to implode.

The cat is batting it with his paw.

 

[shed69]

It is next to shower circuit ,however thinking about it now, it has happened twice while out and once in the night.....

 

[sellers]

Have you tested the RCD?

Try measuring the resistance across L and N 230/32= 7.1875

Any less and it will be tripping.

 

[OnOff]

When does it trip? Off load, when a particular appliance starts up? Any motor / fluorescent loads maybe?

Assuming it all tested out on install is there anything the client has done since and have you redone the tests on that circuit? "I did put a clock/shelf/painting etc up after you left!".

I know it's a pain!

 

[Evans Electric]

Shower is not on long enough to heat up IMHO.

Can there be something you don't know about on the circuit , kicking in ?

Its an oddball this one .

Rodents chewing the cables ??

 

[NozSpark]

Slugs in JB's???

 

[shed69]

No Roland, ah rat fans......

There really doesn't seem to be anything of any real load there ...

They haven't done anything since and remember it was on a B32 on the CU I removed and it never did this...

House about 12 year old

Everything tested out fine on exchange...

It is odd as it hasn't happened when they have been using anything...

There is nothing I don't know about on the circuit.. It really was straight forward...

 

[OnOff]

I would do the tests on the ring again just to make sure. Happens whilst they're out and at night - an expansion / contraction issue maybe as in under load (hot) no trip but as it cools you get the short (iffy bit of T&E?). IR test might pick it up..........

 

[Evans Electric]

What make are the breakers Shedy ?

Don't forget you can get a whole box of faulty stuff , you keep swapping them thinking they can't all be duff!!!

I did a job last month, replace 4 downlight fittings and fit LED lamps instead of the GU10s ....all 4 LEDs duff .

When I was an apprentice , firm sent me to a faulty recessed fluoro in some offices in city centre. Had a look, walked to the wholesaler for 2 tubes ,2 starters . Still not working . Borrow 2 good tubes ,not working , borrow 2 starters and it works !! The donor fitting now doesn't work, fit the new tubes in first fitting and they work. So back to the wholesaler for 2 more starters , walk back, fitting still won't work, try starters in a third fitting and they don't work.

Back to the wholesaler .

Return with two more , still won't work .

Back to the wholesaler to change them, another guy says, " Hey don't serve him those , thats a box of faulty ones "!!!!

Gaffer wouldn't believe me when rollocking me for taking so long!!!

 

[batty]

It could only happen to you Deke I bet Brian was laughing his socks off.

 

[Evans Electric]

I seemed to cop for a load of stuff like that TBH Batts , they never sent the other apprentices on their own , I seemed to to cop for it all the time.

They sent me to refit an electro/ pnumatic valve in a machine , one of our guys had removed it,sent it for repair or whatever then sent me to refit it .

Never seen one before, fitted it , then had to wait for the operator to appear to try it so went round the corner for a cuppa.

Wandered back in , operator says I ran it up but when it got to the bit where the valve operated , it blew a fuse and everything stopped , lights have gone too , you've really ******** it son , the whole machine shop is off.

Well I'm only young and I'm panicking , I test at the dist. bd. and its dead ... I go to this old 100A panel board and thats dead !!

I get the key to the sub , thinking what the hell have I done ....can I fix it before they phone the gaffer .

So I'm in this sub, with the 11,000V incoming stuff on one side and the 415V on the other and I don't know where to look or test ... all I can think is ... I must have connected a dead short in the machine, so I let myself out to the street for a fag ( I smoked then) and a guy comes out from next door and says " I phoned the Electricity Board ... the power will be off for another hour !!!!!!"

FFS ! A string of coincidences, a power cut just as the machine got to the bit controlled by my valve, plus listening to the assumptions of the operator!!

As you say , it could only happen to me .

 

[roys]

Shed do you want a loan of my tong tester, you can set it to min max, leave it for a while and see if it actually does draw a high current.