RCD tripping

[smgeorge]

My RCD trips at irregular intervals (anything from every 30 minutes to 3 hours) and it appears to be caused by the downstairs sockets as sometimes the mcb for the downstairs socket also trips.

It it likely to be a piece of electrical equipment/plug connected to one of the sockets or could it be something else.

Is there a quick way of fault finding it apart from trial and error of connecting and disconnecting each piece of equipmeny connected to a socket. Those devices that do not have a moulded plug I have checked the wiring and they seem fine.

Any help please?

 

[ZenStalinist]

Hmm.. What is on those downstairs sockets:

-Refridgerator?
-Freezer?
-Pump for fish pond
-Washing Machine?
-Dishwasher?
-Anything else involving water?

You need to isolate the appliance, see if there is anything you can unplug or switch off on that circuit and see if the problem goes away. Trial and error coupled with logical deduction is the best method on this one.

 

[smgeorge]

Hmm.. What is on those downstairs sockets:

-Refridgerator?
-Freezer?
-Pump for fish pond
-Washing Machine?
-Dishwasher?
-Anything else involving water?

You need to isolate the appliance, see if there is anything you can unplug or switch off on that circuit and see if the problem goes away. Trial and error coupled with logical deduction is the best method on this one.

Thank you for the reply, I guess what you are saying is that it is most likely to be something related to water? We have a washing machine and fridge freezer, with the washing machine plugged in the cupboard under the sink. I guess these two devices would be agood starting point.

The other point I did not make before is that nothing has changed in the past year in terms of devices connected to sockets and this fault has suddenly starting happening.

Thanks for your help

 

[TexMex]

Since this is an intermittent fault, it could be very difficult to establish that the item you've just plugged in is causing the problem. (it may not play ball when you want it to).

You could try, instead, getting one of those rcd things that plug into a socket and plug an appliance into that. Leave untill the next incident. If it hasn't tripped, move it on to the next appliance. Hopefully, sooner or later, it will trip and therefore unmask the beastly piece of apparatus.

 

[phil_ballard]

... provided it trips before the one in the CU?

 

[ZenStalinist]

Yeah, usually the one in the CU trips first, so unless you find a more sensitive plug in rcd it may not help.

 

[dingbat]

Yeah, usually the one in the CU trips first, so unless you find a more sensitive plug in rcd it may not help.

Yeah, discrimination is important. My favourite example of getting it wrong is the college 2391 test rig - the whole supply is protected by a 30mA RCD, which happens to be more sensitive than the RCD's in the rig which, therefore, can't be properly tested! (And, of course, only certain loop testers can be used; all the college ones trip out the RCD!)

 

[TexMex]

Do the plug in RCDs come in different flavours, (to stop big shocks or little shocks) or are they all pretty standard.

 

[phil_ballard]

Aren't they all 30mA?

 

[plugwash]

most plugins are 30ma trip though some specialist ones may be 10ma trip

however unless the upstream rcd is a type S (time delay) you have a pretty good chance of tripping them both anyway

 

[TexMex]

Both would still be OK though eh? For the sake of the diagnosis.