Weird Rcd Tripping,help

[chris76]

Hi all

Got a problem with a kitchen i fitted a couple of years ago.
the customer got their own electrician to fit a new ring in the kitchen on its 2 way rcd protected box along with the lighting.

i went back on friday to change the sink unit and fit a new belfast sink.
Now they had a double socket fitted to the sink unit which had a washer and dishwasher connected,which i disconnected so i could change the unit.

Got everything back together again plugged them both in and it knocked the rcd out,so i checked polarity and to make sure i hadnt knicked a cable which were all fine and i changed the socket.

Everything else in the kitchen works fine and if i plug either the dishwasher or washing machine in by themselves they work fine but the minute i plug the other appliance in it trips out.

i can even run all appliances in the kitchen. And then go under the sink plug ONE of the problem appliances along with a drill and they work fine,but when i swap my drill for the other appliance it trips out.

And iv tried running an extension to 1 appliance and leaving the other plugged in under the sink

Now the cables will have got wet but i dired it all out as best as i could and even had a hair dryer under there too

I hope that makes sense and someone can help

 

[mattg4321]

Have you IR tested the circuit?

 

[UKMeterman]

Pat test the appliances and IR the circuit, I have known of fried mice in domestic appliances. Also check for any N-E shorts in the fixed wiring, lastly ramp test the RCD.

 

[chris76]

TBH no,i didnt have any testing gear on me,all i was doing was replacing a sink and unit so just unscrewed the socket and refitted it.

but the circuit must me fine everything else in kitchen runs away merrily until i plug them both in at same time (even if they are just in standby)

 

[Pete999]

Have you IR tested the circuit?

Chris is a kitchen fitter Matt what do you think?

 

[chris76]

do you think both appliances casing and cables may have been wet so with them both combined it was enough to knock the rcd out?

 

[tony mc]

It could be a number of things but without the correct test equipment I am affraid you could be wasting your time.

Its time to get someone in with the right equipment and knowledge to find out what the problem is!

 

[chris76]

yeah but surely the kitchen wiring is fine otherwise it would trip out.

all i did was unscrew a socket and refit it.

i dont have any pat testing equipment or any experience of pat testing

 

[mattg4321]

Chris is a kitchen fitter Matt what do you think?

I can see where you're coming from but it was a more polite way of saying stop messing around with things you don't really understand!

 

[davesparks]

Well if you got it wet then it's not too surprising that it's tripping now is it?

As said earlier test the appliances to find which one it is and the take appropriate action, which might well be replacing the appliance.


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[Darkwood]

I just approved several posts by the OP so anyone posting in the thread may just want to browse over it to catch up with his replies.

 

[chris76]

I can see where you're coming from but it was a more polite way of saying stop messing around with things you don't really understand!

Ok can you just read through my posts again and tell me your gut feeling of the problem

 

[Midwest]

It could be something you've done screwing back the socket, it could be an accumulative effect of faulty appliances (which your customer could of 'failed' to tell you about prior to you fitting the new sink), it could be a fault on the RFC, it could be a faulty RCD, it could even be a fault on the lighting circuit (something I learnt on this forum).

But you fitted the kitchen and didn't install the electrical work. As others have advised, your customer needs to get their electrician back to properly test with the appropriate test equipment.

It is not admitting defeat, just accepting ones limitations, and I don't mean that in derogatory way. The electrician will steal all the glory, if their find the fault (which might be something you have done, which is troubling you, understandably). But turning it around, I suspect you would have to have refitted the sink, if they had employed the electrician to install said sink.

 

[chris76]

It could be something you've done screwing back the socket, it could be an accumulative effect of faulty appliances (which your customer could of 'failed' to tell you about prior to you fitting the new sink), it could be a fault on the RFC, it could be a faulty RCD, it could even be a fault on the lighting circuit (something I learnt on this forum).

But you fitted the kitchen and didn't install the electrical work. As others have advised, your customer needs to get their electrician back to properly test with the appropriate test equipment.

It is not admitting defeat, just accepting ones limitations, and I don't mean that in derogatory way. The electrician will steal all the glory, if their find the fault (which might be something you have done, which is troubling you, understandably). But turning it around, I suspect you would have to have refitted the sink, if they had employed the electrician to install said sink.

Thanks for the reply midwest.

It trips with the socket front forward still.
ITs Just frustrating because im getting the "it was ok before you touched it" treatment. and id like to sort it out for them.

they are away on holiday atm and their daughter is just swapping the plugs over when she wants to use either appliance.

can i ask what order of tests others would do to finfd the problem?

thanks for your help

 

[telectrix]

1. with everything unplugged, IR test the circuit.

2. Test the RCD, both for times and tripping threshold.

3. PAT test the 2 appliances.

 

[Richard Burns]

Effectively here the work you did should not have affected the electrical circuit.
However the RCD is now tripping.
An RCD will trip because of a low fault current to earth (actually a difference of current in line /neutral)
Because the socket will work with anything but those two appliances it tends to indicate that there is a problem with the appliances not the circuit.
Since you say that the appliances and the supply cords would have got wet and since water ingress is a primary cause of an RCD tripping it would seem likely that there is water either in the plug or in the appliance itself, depending on how the appliances got wet. If they are only damp then this may be limiting the fault current to below 30mA for each appliance but over 30mA for both, a bit unlikely but possible.
Another possible alternative is that the supply cords have been damaged by being run over or such.

Without testing the appliances for earth leakage it is not really possible to tell the fault cause.

 

[rolyberkin]

Without test equipment you may as well consult a crystal ball, I had a similar situation where there had been some work done in a kitchen and just by chance there was a neutral to earth fault on a cable in between two plugs which reared its head at the same time Unconnected to the work which had been completed) . It was pure coincidence that it happened at the same time but it did, some quick tests isolated the offending cable run. They had even had an appliance repair man in as they were sure it was the washing machine at fault as it was intermittent.

 

[Midwest]

Sound advice.

OP, you mention 'Now the cables will have got wet but i dired it all out as best as i could and even had a hair dryer under there too'; what was that caused by?

Were the said appliances both plugged in and turned on before you started? I think we've all had the "it was ok before you touched it", and the customer knowingly waits for some soul to come along and inherit the established fault!

If you done as little as reconnecting a socket (as long as your sure you've reconnected it correctly), and the fault only occurs when plugging in the two appliances together, than as suggested it would appear to be with cumulative earth leakage. However, you will need the appropriate test equipment and skills to locate the fault.

Call the electrician, and learn by you mistakes, however well meaning were your actions.

 

[EastAnglian]

Replace the socket under the sink as a first guess given all the clues above. Sounds like a mechanical failure in the socket causing an earth fault when 2 plug tops inserted. You can eliminate the appliances from the guessing game by pluggingthem into other sockets in the kitchen.

 

[Wilko]

If I didn't have test kit, I'd confirm if the RCD trips when one or both appliances are supplied from another outlet on the kitchen ring (via short extension lead?) . If it can be proven way that it's the appliances you may go down a different path for fault fix. Just a thought. Cheers, David.