cooker tripping

[aaelectric]

Have been to a job where the hob has a dedicated circuit protected by rcd. each time we flick the cooker switch the rcd trips. If you leave switch in on position and use hob its fine, does not trip. I have checked all connections in fuseboard and cooker swith and outlet and all are tight. I have replaced cooker switch as i thought this may have been faulty but did not solve the issue. the client had an appliance engineer round to check hob and all was ok?

 

[goldie]

I would test the wiring then. Or possibly rcd faulty

 

[telectrix]

what's the current rating of the |RCD? i mean the amps, not mA.

 

[Deleted member 9648]

IR test the circuit.....It's not unknown for a slight surge when switching to bridge a low IR fault and trip an RCD...but left on it doesnt trip. If you dont pick anything up @500v try 1000v..(assuming no sensitive electronics),sometimes this will pick up an intermittent IR issue when 500v shows clear.

 

[MarkieSparkie]

If all your testing reveals no apparent fault, then the tripping could be caused by the double pole switch in the CCU opening the neutral pole before the live pole ...
[FONT=&amp]In the real world, the situation is complicated by the residual capacitances and leakage paths.
N-E residual capacitance exists in all installations, but the leakage through this capacitance is negligible because of the low potential (almost zero) between N-E. When the N pole of a double pole switch opens, the voltage across this capacitance will rise suddenly with a subsequent increase in N-E leakage current through this capacitance. This increase will be at a maximum if the switch N pole opens before the L pole. As the switch contacts open they will arc, causing HF voltage spikes, raising the N-E leakage even higher. If the switch has a slow break characteristic, often found in domestic switch gear, the effect will be even greater.
This phenomenon is most commonly witnessed in distribution boards with a separate front end conventional RCD. Where opening the DB Main Switch causes a high voltage (near full mains potential) to charge the N-E capacitance of the whole installation, easily causing enough leakage current to flow to trip the RCD. [/FONT]

 

[Specialist]

Have been to a job where the hob has a dedicated circuit protected by rcd. each time we flick the cooker switch the rcd trips. If you leave switch in on position and use hob its fine, does not trip. I have checked all connections in fuseboard and cooker swith and outlet and all are tight. I have replaced cooker switch as i thought this may have been faulty but did not solve the issue. the client had an appliance engineer round to check hob and all was ok?

Just a thought, but what did the "Appliance Engineer" use to test the Hob ? the majority of appliance engineers still don't carry a Megger of any sort & just use a Multimeter for testing. Might be an idea to carry out your own IR test on the Hob.

 

[aaelectric]

I have tested circuit at 500v dc will good readings the r c d is 80 amps 30ma
The hob works and does not cause the r c d to trip when in use.

 

[mickytuff]

i would test the rcd, then insulation/resistance test the wiring, if alls ok i would check that rcd protecting the problem circuit isnt covering any other circuits that may actually be the problem, ie with a low n e reading, thus when the switch is pressed (load applied) causes the rcd to trip, i came across this bout 5 years ago and it took a while to find, but hey thats experience, we all dont know everything, if we did we would be liars, so i hope this helps my compardrey.