RCBO tripping fault

[ktguk]

a lad in work changed a CU today, then called me over to say that rcd protecting the sockets (1 ring for whole house) was tripping thought was a the kettle as it stopped when i plugged it back in but then the fridge caused it to trip, but on the other (side) rcd protecting the cooker with socket unit wasnt tripping when kettle was plugged in. then without the kettle/fridge (just incase they were both faulty) tried the washer, dryer, microwave still good but then the TV tripped in, a brand new 42" sony. whats going on here??

have done :

continuity (low ohms) between the N bars - clear

continuity (low ohms) between the live bars - clear

RCD ramp test fail tripping at 33ms - replaced rcd still 33ms

last thing in the day bypasssed rcd :coffee going back first thing tomorrow headbang

 

[sparkytim]

Probably a N-E fault this gives this result as RCD trips when ANY current flows in the circuit when ANY appliance kicks in.

 

[vandalay]

Have you done a IR test and should them ramp test results be in miliamps not secs. ?

 

[ADS]

a lad in work changed a CU today, then called me over to say that rcd protecting the sockets (1 ring for whole house) was tripping thought was a the kettle as it stopped when i plugged it back in but then the fridge caused it to trip, but on the other (side) rcd protecting the cooker with socket unit wasnt tripping when kettle was plugged in. then without the kettle/fridge (just incase they were both faulty) tried the washer, dryer, microwave still good but then the TV tripped in, a brand new 42" sony. whats going on here??have done :

continuity (low ohms) between the N bars - clear

continuity (low ohms) between the live bars - clear

RCD ramp test fail tripping at 33ms - replaced rcd still 33ms

last thing in the day bypasssed rcd :coffee going back first thing tomorrow headbang

Ramp test measures in mA not mS

IR tests are what you should be doing.

I would agree with Sparkytim - neutral/earth fault as these are load dependant

 

[ktguk]

repaired falut today was a N-E fault but on the lighting circuit which was on same N bar (RCD), screw through a cable holding up DIY light fitting shorting N-E. how does that work?

 

[Apache]

repaired falut today was a N-E fault but on the lighting circuit which was on same N bar (RCD), screw through a cable holding up DIY light fitting shorting N-E. how does that work?

N&E @ same potential as linked at cu?

 

[ianmacd]

Parallel paths back to source therefore imbalance in L&N though RCD so will trip as it should.

 

[sparkytim]

It diverts some current down the Earth instead of coming back up thru the N so the RCD sees this as an imbalance and trips.

Only trips when some current flows in the circuit(s)

So all ok UNTILL something switches on.

 

[ianmacd]

And since all N's for that RCD are linked then it can by anything switched on on any of the circuits on that RCD.

 

[sparkytim]

N&E @ same potential as linked at cu?

Hi Pach

NO N&E Not linked at CU if TNCS they are linked at Service Head or TNS Linked at supply transformer.

Both these are on SUPPLY side of RCD so the RCD does not see it.

ok?