Kitchen Ring earth fault?

[Ross1]

Hi guys,

Customer woke up this morning with the Main switch/RCD tripped. He narrowed the problem down to the kitcken ring so He unplugged all the counter top appliances and switched all the big under counter appliances off at the switches.

I got there and turned the mcb on then plugged the toaster in first and the RCD tripped. I then punplugged the toaster and reset the RCD. I then plugged everything in the kitchen in One by one and left each appliance plugged in individually for 5 - 10 mins each, the only thing that that tripped the RCD was when I plugged the freezer in.

I checked the wiring behind each socket and all was ok. So I plugged everything in except for the freezer and the RCD didnt trip. I waited for nearly an hour and no trip even with the toaster plugged in and the switch turned on.

I didnt have any test equipment on me but I`m going back tmrw with test equipment, so my question is can anybody advise on possibley the quickest way to iddentify the cause of the fault?

Thanks

 

[steve447]

agree with tel,otherwise the diy sheds could not sell any electrical accessories as the diy bloke couldnt change a socket without having to call someone out to test and inspect/issue a mwc.

Get your point however they still sell Consumer Units to anyone. See a fully loaded G.E one for £50 in there the other week.
Surely a board change is not considered like for like is it?

 

[Spoon242]

Have you tried PAT testing the appliances.

My apologies for swearing!

If your IR tests are acceptable, PAT testing is another option.

There I did it again, swearing!

 

[Deleted member 9648]

Get your point however they still sell Consumer Units to anyone. See a fully loaded G.E one for £50 in there the other week.
Surely a board change is not considered like for like is it?

Could be I suppose, if the configuration and protective devices are all identical to the existing...ie a replacement due to damage to the existing....a CU upgrade would not be like for like though.

 

[Ross1]

Thanks to most of you guys for all your responses apart from the odd 1 or 2 of you. If you got nothing helpful to say, I`d rather you not comment on my threads.


I was back on the job today with my tester, I done ring end to end continuity 0.51 L-L 0.52 N-N 0.84 E-E. IR test, lowest reading i got was 250M Ohm.


Everything in the house stays on, under load aswell untill I plug the freezer in and.....boom RCD trips within 30secs. So my conclusion is the freezer is the problem ( its a smeg under counter job if that helps ) Ive never claimed to be an 20 - 40 year experienced spark, thats why I am on this forum which I find a great source of info from lots of experienced sparks.

Im new to testing and fault finding so am I missing something Guys?

 

[chopper]

most probably be the freezer pal, as said above if all IR test is clear l-e, n-e, then circuit is fine,
just to prove you have found the fault a PAT on the applience would show leakage to earth,

 

[Ross1]

most probably be the freezer pal, as said above if all IR test is clear l-e, n-e, then circuit is fine,
just to prove you have found the fault a PAT on the applience would show leakage to earth,

Thanks chopper, never done PAT and aint got the equipment. Any tests I could do with my multifunction tester on the appliance mate. Its my mates house and dont want him to have to call out a PAT man and part with his cash.

Thanks

 

[chopper]

not too sure , maybe try a continuity test between l-e , and n-e see iff anything shows up, not sure if you could do an IR TEST ON THE APPLIENCE AT 230V

 

[spark 68]

Hi mate,

you could join L-N of the appliance and IR test @ 500v (test @ 250V first) to earth/metalwork of the appliance, it would be better if the appliance was disconnected from the fixed wiring for this, as this is all a PAT test would do with regards to the IR test part. and see what you get.

 

[Ross1]

Hi mate,

you could join L-N of the appliance and IR test @ 500v (test @ 250V first) to earth/metalwork of the appliance, it would be better if the appliance was disconnected from the fixed wiring for this, as this is all a PAT test would do with regards to the IR test part. and see what you get.

cheers mate, do you think that anything under 2M Ohm could be suspect as is usually the case?

 

[spark 68]

under 2M Ohm could be suspect as is usually the case?

I would expect anything less than 1 Meg for class 1 to be suspect, others may wish to correct me if Iam wrong.

This method does not replace a PAT test per se, but will show up faulty equipment.

Ps. if the appliance is faulty, I would expect your IR result to be a lot lower than 1 Meg, as a 30mA RCD will trip with a combined 'leakage resistance to earth' anywhere from about 8K ohms to about 15K ohms, depending on the actual RCD tripping current checked on the Ramp test

 

[Mark_Burgess]

Ahh the freezer, at least you know what it is!!
What you pretty much found but couldn't confirm first time.

 

[richy3333]

the other thing to note is the MWC itself asks for "details of the modified circuit". replacing a fitting /accessory is not modifying the circuit. therefore, IMO, no certificate is required (although i do not dispute the idea that it may be advantageous to complete a test of the circuit and issue a MW

edit:sorry, double post.

Hi Tel.

Just looking at the MWC in the BRB (page 335). Could you clarify where it refers to 'details of modified circuit' in the certificate?

 

[Knobhead]

Thanks to most of you guys for all your responses apart from the odd 1 or 2 of you. If you got nothing helpful to say, I`d rather you not comment on my threads.


I was back on the job today with my tester, I done ring end to end continuity 0.51 L-L 0.52 N-N 0.84 E-E. IR test, lowest reading i got was 250M Ohm.


Everything in the house stays on, under load aswell untill I plug the freezer in and.....boom RCD trips within 30secs. So my conclusion is the freezer is the problem ( its a smeg under counter job if that helps ) Ive never claimed to be an 20 - 40 year experienced spark, thats why I am on this forum which I find a great source of info from lots of experienced sparks.

Im new to testing and fault finding so am I missing something Guys?

I stand vindicated!

As to are you missing something, it’s just experience which will come with time.