fault finder

[casamena]

Happy new year to all.

yesterday my elderly next door neighbour said that her fridge freezer wasn't working. i went to have a look and found that an rcd had triped. ( 2 way consumer unit 1 rcd for 3 socket circuits ) i replaced the mcb for the down stairs sockets ciruit that was at fault hoping that it was just a faulty mcb. it triped again, i then left it off and re-engaged the rcd. the circuit at fault 16 amp mcb was labeled downstairs sockets, but they were all working fine so i went around to every socket in the house but these were also fine . any help on this appreciated thanks.

 

[Alarm]

Should you have been doing this?

 

[casamena]

yes

 

[BigJon]

Its highly unlikely the MCB's at fault.
Unplug everything, reset RCD and then plug in things one at a time to see if the RCD trips.
Chances are its an appliance thats at fault.

 

[martinxxxxxx]

Swapping things out at random is hardly going to help the situation.

Fault finding should be done in a logical manner otherwise you'll create another fault in the process and end up with seemingly illogical results. In other words chasing your tail around the place.

You need a insulation resistance meter and a possibly a pat tester (sic) for starters really, but more importantly a better approach than you are currently using, Can you not tell your neighbour to call an electrician tommorow?

 

[Alarm]

Well with no testing equipment the correct way would to do as Big J says . Unplug everything reset and add items one at a time.

Of course you need the other tests but just changing a mcb because you HOPE that might be the problem!!!

Hence the question "Should you have been doing this?".

 

[EFLImpudence]

found that an rcd had triped. ( 2 way consumer unit 1 rcd for 3 socket circuits )
i replaced the mcb for the down stairs sockets ciruit that was at fault hoping that it was just a faulty mcb.
it triped again,
i then left it off and re-engaged the rcd.
the circuit at fault 16 amp mcb was labeled downstairs sockets, but they were all working fine

That doesn't make sense.

 

[westie101]

So it seems that folk are telling the OP to look for a fault that doesn't exist!

He found an MCB tripped along with the RCD, His "replaced the MCB" was switching it back on.

He has left it switched OFF and the RCD has stayed in the ON position.

However the MCB is labelled "Downstairs Sockets" yet all the sockets in the house are ON and OK.

Seems like a case of bad labelling to me. Though there may be something in the house not working

 

[Alarm]

Alright, would you suggest swapping the mcb out as a "first step" anyway?

 

[westie101]

Well it seems that if the MCB is closed the RCD trips, so there must (??) be some wiring attached to it. Surely the first step is to find out what is actually connected and go from there.
All we know is that it is a 16A MCB wrongly labelled as "Downstairs Sockets" and it appears to control a faulty circuit

 

[casamena]

all appliances were un-plugged so i dont believe a pat tester was needed. i dont do domestic work. but the company i work for mainly repair electric motors and work in other electrical sides that are covered from various part p schemes. im off work and don't have the IR tester so this was why i was hoping that it was just the £7 mcb. if the unit was labelled better it would of been more helpful . was confused as to why all of the installation would work when the mcb was off.

 

[casamena]

Well it seems that if the MCB is closed the RCD trips,

no the rcd doesn't trip when the mcb is closed.

 

[PrenticeBoyofDerry]

Does the RCD trip when all equipment is unplugged?
Does it only trip when F/F is on load?
Could be faulty appliance, check flex for damage, plug and for any moisture.

 

[333rocky333]

A 16amp mcb even if faulty is unlikely to trip an rcd so at this stage i would not change it.

You say the rcd tripped off but
Did the actual 16 amp mcb trip at any time

 

[casamena]

You say the rcd tripped off but
Did the actual 16 amp mcb trip at any time[/quote]

yes