Tripping RCD

[jabberwocki]

Would really appreciate any help. Have had a problem with tripping RCD for months now. No electrical work done on the house.
After checking on numerous occasions narrowed it down to Kitchen Sockets. Have today traced it to dishwasher. When dishwasher is on trips RCD when off no problem. couple of questions.

1. As its always RCD tripping and no MCBs trip I asuume there is earth leakage in the DW and not a case of overload. Washer and other heavy appliances are in the utility room on a seperate MCB so would not contribute to the load.

2. RCD has tripped when the dishwasher has not been running but was plugged in and switched on. ( As the machine would be live I would take it this could happen am I right?).
If I am right about the above will probably get a new dishwasher as this one is pretty old. Do you think that would solve it? Anything else I should check before spending the money? THANKS

 

[GaryMo]

Ideally you would have an Insulation Resistance test carried out on your fixed wiring. This would either highlight a problem or eliminate your fixed wiring as being the source of your problem.
Also, an RCD test would be advised - trip times and ramp.

All that aside, you're thinking logically and it probably is your dishwasher.

 

[jabberwocki]

Thanks for that Garymo. I did try running it on an extension into another socket (seperate circuit & mcb) still tripping. Does this mean it's likely not to be the fixed wiring? If there is a chance there is a problem with fixed would rather get it checked. Have checked the backs of all sockets to confirm all wires tight and connected that's about as far as my leccy knowledge takes me. Thanks

 

[GaryMo]

It seems that you're confident that the fault is only occuring with the dishwasher connected and whilst unconnected there's no issues.
If that's the case then I wouldn't worry too much about your fixed wiring.

However, it's recommended that the maximum time between inspection and testing of domestic installations is 10 years or change of occupancy (whichever comes sooner). This is acheived by having a Periodic Inspection Report (PIR) carried out.

 

[jabberwocki]

Thanks garymo.
When I moved in here (18 months ago) the seller had just built an extension(he was a builder) and whilst extending the wiring had it all checked(1980s property). He supplied me with all the paperwork so I would assume ok although I have noted your comments on having the wiring checked. Definitel;y only trips when the dishwasher is plugged in have just spent all afternoon checking in different socket etc. It also trips whilst the DW not working but switched on at the socket. When switched off or uplugged no problem at all. Have changed the plug and checked no cuts in the wiring which is about all I can do. looks like a new one. OH will be happy as this one is looking a bit tatty. Thanks for your help.

 

[ericmark]

If there is a earth neutral fault on any appliance then as the current draw increases the likely hood that it causes a RCD to trip increases. Since a dish washer draws a lot of current it could when switched on highlight a problem with another appliance rather being dish washer it's self.

From your account does seem likely it is the dish washer. However if you swapped it only to find new one doing the same you would not be happy and so it would be better if you could get it tested.