RCD trip help

[sirocco]

Just been called out investigate RCD tripping on downstairs ring at my parents it just went in the early hours with no history. Have unplugged all appliances from the 10 sockets on this ring and switched all sockets off. There are no other appliances fed from this ring other than those plugged in via sockets. There are 3 other circuits protected by the same RCD in the CU ie Shower, Cooker and upstairs ring, these are all functioning normally and don't trip the RCD. I have substituted the downstairs ring MCB but the circuit still trips the RCD immediately when the MCB is switched on with nothing plugged into the sockets. My next step is to disconnect the ring, split the dead ring at the midpoint and test each half, but before doing this I removed the 2 CPCs for the ring at the CU from the earth bar and the circuit now stays on and doesn't trip. Before I plough on , disconnect the phase and neutrals and do dead circuit testing is there anyway that I can identify why the disconnection of the CPCs allows the ring to operate? Graham

 

[GLENNSPARK]

Whats a Z1 test ?


Something from Top Gear?

yes....its called `see how fast you can get round the circuit`....

 

[electric will]

Whats a Z1 test ?


Something from Top Gear?

maybe something to do with the new BMW.

 

[power ranger]

If the OP is using a fluke mft and doing dead tests then he would be setting his tester to "Rlo" for a low ohm continuity test and not Z1 as this is for loop tests.

Im thinking that it could have been a "pinched" Line conductor on one of his steel k/o boxes, and he has just been lucky that when screwing the socket outlets back after testing the orientation of the conductor has been altered and now not causing a L-E fault.

Just as a note to the OP. If you do go back and carry out IR tests, then leave the CPCs in the earth bar when testing!

 

[GLENNSPARK]

If the OP is using a fluke mft and doing dead tests then he would be setting his tester to "Rlo" for a low ohm continuity test and not Z1 as this is for loop tests.

Im thinking that it could have been a "pinched" Line conductor on one of his steel k/o boxes, and he has just been lucky that when screwing the socket outlets back after testing the orientation of the conductor has been altered and now not causing a L-E fault.

Just as a note to the OP. If you do go back and carry out IR tests, then leave the CPCs in the earth bar when testing!

aye and if it goes to fault while he `tests` this circuit with CPCs disconnected he could end up pinching one off n all (involunatry)

 

[Deleted member 9648]

Cant believe some of the ceerap posted on here....the OP has a tripping RCD and he STILL hasnt IR tested???.....thats the first effin' thing to do for $%*&'s sake!

 

[sirocco]

If the OP is using a fluke mft and doing dead tests then he would be setting his tester to "Rlo" for a low ohm continuity test and not Z1 as this is for loop tests.

Im thinking that it could have been a "pinched" Line conductor on one of his steel k/o boxes, and he has just been lucky that when screwing the socket outlets back after testing the orientation of the conductor has been altered and now not causing a L-E fault.

Just as a note to the OP. If you do go back and carry out IR tests, then leave the CPCs in the earth bar when testing!

Obviously used the low resistance setting for the resistance tests and did the loop impedance at a socket using Zl no trip setting once circuit was all reconnected and live. Is leaving the CPCs in the earth bar best practice? I thought that to test the insulation resistance of a particular circuit that each element to be tested LE and NE needed the 2 conductors and CPC to be fully isolated to be sure that readings related to that length of cable only. ?

 

[power ranger]

Sorry got to be quick, but if you removed cpc,s from met, tested IR, then how would you know if there was a fault from a live conductor to any extraneous metal in that installation?
Therefore by keeping the cpc's in the met and putting your test lead on that and your other lead on the circuits L or N, then you will be verifying that all earth parallel paths are isolated from live conductors.

 

[bertt]

Hi,

The RCD-30mA if it is for a few circuits in your Consumer Unit , actually will make a vect.sum(a result) of all your possible leakings about circuits on L&N(3,4...circuits).
I don't know the history of your problem linked with particular event or not during the day,night. Please ask your parents when they observed the missing of power.. what they did then? Could be helpful.
About your (new, with RCDs) Consumer unit:
please double check inside the CU wrong tightening of wires It could make overheating and or false connections.

So,
I.
- One by one the modules MCBs and next RCDs 'OFF' about Consumer Unit.
- Then Main Switch OFF
- open the CU box
- Visual proper inspection of all modules as integrity(colour, shape) and IN/OUTs contacts and tightening. Use the electrician light torch(head one) ,screwdrivers....
- search any clues of overheating area IN, OUTs, MCBs, RCD.
if ok all above follow next steps...

- remove the circuit as wires(phase & neutral)you suspect as cause of RCD tripping. From OUT MCB circuit.

II.
- reconnect the Main Switch(ON)
-Then in order the RCD where is comming your circuit through MCB.
and after the MCB itself .Your circuit still away from OUT MCB who belongs.

A- Now, if the RCD is tripping after MCB circuit swiched 'ON' it is something inside the Consumer unit the problem not the circuit.
if not ..
B- add all the others circuits(switch 'ON')from same RCD group.If same, RCD it is not tripping the cause it is somewhere on circuit but I bet on Consumer unit connections problem.
(Don't forget after to reconnect the circuites.
Main switch 'off ' reconnect the wires proprely L,N to MCB,.
Switch ON Main switch and one by one RCDs and after MCBs. Double check and Test IN OUTs and TEST RCD .Close the Consumer Unit BOX.
Thank you.

All the best.

bertt.imp:

 

[KAS1]

can someone translate the above please lol

 

[Engineer54]

can someone translate the above please lol

You and me Both!! ..lol!!

 

[KAS1]

He's lost me, it looks like a step by step guide to nowhere IMO lol

 

[dave1064]

Sounds like a line to earth fault. Insulation resistance test should find this out.

 

[babylonsBurning]

Hey Dave
Im guessing u are new to this thread, most of us said exactly this.
Then something weird happened, if you want a laugh read all the previous posts and you will be as confused as the rest of us!!!!!!!

 

[Outspoken]

Just been called out investigate RCD tripping on downstairs ring at my parents it just went in the early hours with no history. Have unplugged all appliances from the 10 sockets on this ring and switched all sockets off. There are no other appliances fed from this ring other than those plugged in via sockets. There are 3 other circuits protected by the same RCD in the CU ie Shower, Cooker and upstairs ring, these are all functioning normally and don't trip the RCD. I have substituted the downstairs ring MCB but the circuit still trips the RCD immediately when the MCB is switched on with nothing plugged into the sockets. My next step is to disconnect the ring, split the dead ring at the midpoint and test each half, but before doing this I removed the 2 CPCs for the ring at the CU from the earth bar and the circuit now stays on and doesn't trip. Before I plough on , disconnect the phase and neutrals and do dead circuit testing is there anyway that I can identify why the disconnection of the CPCs allows the ring to operate? Graham

Could call out an experienced Electrician I suppose...this should be a doddle to locate the fault. As others have said it is clearly an L-E fault so finding it should be straight forward, if a pain in the rear, so I do not get the coming here asking help to solve something that should be solvable by a decently trained 3rd year apprentice...

 

[sirocco]

Sorry got to be quick, but if you removed cpc,s from met, tested IR, then how would you know if there was a fault from a live conductor to any extraneous metal in that installation?
Therefore by keeping the cpc's in the met and putting your test lead on that and your other lead on the circuits L or N, then you will be verifying that all earth parallel paths are isolated from live conductors.

Very Good point esp if carrying out an Ir on a full installation. If you've narrowed the problem down to one ring and need to check Ir on wiring between sockets , would it still be best to leave the cpcs connected I the sockets and just remove the conductors between the suspect sockets to Ir check LE and LN leakages?