Dishwasher still tripping after leak repair

[MrBrindle]

Hi all,

We had a leak in our kitchen a month or so ago. It was a slow leak from a HW pipe, and had probably been going on for weeks / months. Damage is quite minimal though, with most of the dampness going across the floor, and some in the wall along the bottom. Some of the insulation behind the plasterboard was also a bit wet. It's a timber framed house.

What alerted us to the leak was that the dishwasher kept tripping the RCD. The dishwasher socket is situated underneath where the leaking pipe was horizontally going, so it's possible that the water could have trickled down the pipe and into the socket. The main switch to the dishwasher is by the oven and fridge freezer switches. (I'm not sure what the technical term is for that electrical setup) I've taken the socket off the wall and inspected for any burning marks or damage, but all looks ok.

We left the area to dry using a dehumidifier for a good week, before plugging everything back in.However the dishwasher, when running, is still tripping the RCD intermittently - there's no pattern to it.

We've had a Bosch engineer out, as the dishwasher is still under warranty being only 4 months old, and he said it's working fine.

I did plug a kettle into the dishwasher plug and boiled a few times to see if it would trip, but nothing. My next troubleshooting job will be to pull the dishwasher out and plug into another wall socket and run, to rule out if it's definitely not the dishwasher.

Is it best to just get an electrician out? What could be faulty here? The socket?

I'm getting paranoid there's some major issue with the electrics behind the bloody cabinets now!

Any advice greatly appreciated.

 

[JohnD]

I did plug a kettle into the dishwasher plug and boiled a few times to see if it would trip, but nothing.

you mean socket

water can also get into the appliance plug.

does the trip start during a wash cycle, about 10 minutes in, but not on a rinse-and-hold?

 

[MrBrindle]

water can also get into the plug.

does the trip start during a wash cycle, about 10 minutes in, but not on a rinse-and-hold?

Thanks for the reply.

It's very intermittent. Sometimes it does trip 10 minutes in, but other times it runs fine for 30 minutes, then trips! It doesn't seem to colerate with any function on the machine which makes it strange. If it tripped when the water heats up that would be something, but it just seems completely at random.

 

[sparkwright]

You definitely should check the plug and socket for water ingress and any other possible faults.

However, it is quite possible there was always a (completely unrelated) fault on the dishwasher itself, such as a leak with water getting into it somewhere that doesn't always dry out.

 

[MrBrindle]

You definitely should check the plug and socket for water ingress and any other possible faults.

However, it is quite possible there was always a (completely unrelated) fault on the dishwasher itself, such as a leak with water getting into it somewhere that doesn't always dry out.

No worries. I wasn't home when the Bosch engineer called, however my partner said he put something in the wall socket to test the electric. (?!) No idea what though.

Will probably have to get an electrician out then. Hopefully it's something simple like a socket replacement.

In the meantime, is it reasonably safe to run an extension lead to the dishwasher to use?

 

[JohnD]

give it a try.

a different circuit might be good

 

[SUNRAY]

In my experience, random RCD tripping for washing machines and dishwashers has so far always been the mains filter, just inside the machine by the mains cable.

I do understand the water leak history but of course it may not have been the water causing the tripping, just a fortuitous coincidence.

Just my observation. But it did result in me changing over to all RCBO.

 

[ericmark]

As inferred by others but not spelled out, a earth to neutral leak will likely only show up when there is a heavy load, and dishwasher is heavy load. Could find kettle will also trip the RCD if plugged into same socket.

 

[MrBrindle]

In my experience, random RCD tripping for washing machines and dishwashers has so far always been the mains filter, just inside the machine by the mains cable.

I do understand the water leak history but of course it may not have been the water causing the tripping, just a fortuitous coincidence.

Just my observation. But it did result in me changing over to all RCBO.

How easy is it to diagnose a fault in the mains filter?? Bosch have already been out to check and said the machine is working fine.

 

[MrBrindle]

As inferred by others but not spelled out, a earth to neutral leak will likely only show up when there is a heavy load, and dishwasher is heavy load. Could find kettle will also trip the RCD if plugged into same socket.

Sorry for being uninformed, but what is an 'earth to neutral leak'?

 

[EFLImpudence]

It should be Neutral to Earth leakage - or Line to Earth leakage.

That is: current that should be flowing in the Line and Neutral conductors escapes to Earth - not necessarily the CPC(Earth wire).

 

[SUNRAY]

Sorry for being uninformed, but what is an 'earth to neutral leak'?

There's no need to apologise for asking about something you don't understand, that is why we are here to help.
Normally the current flowing in the RCD is balanced and the earth lead carries no current, basically it is only there for safety... or just in case:

However if there is a fault between neutral and earth after the RCD, the earth wire may carry some of the current:

The current in the RCD is not then balanced and will do it's job of disconecting.

EDIT: Thanks to EFL for correctly pointing out the 'leak' may not be to the earth wire.

 

[SUNRAY]

How easy is it to diagnose a fault in the mains filter?? Bosch have already been out to check and said the machine is working fine.

Actually it's not that easy, a PAT test may show it but in my experience is unlikely to.
What I usually do now will be frowned upon by some members on here: I remove the filter from circuit and run the machine normally for a few days but only long enough to convince me it is, or isn't, the fault.
They usually involve pushfit spade connectors and after taking a picture to show the correct installation it may be easily configured to take it out of circuit.


My very first was my dishwasher and I'd get random trips at anytime, usually at night, but it may be daily or not for a month. I spent months messing about and swapping circuits in my consumer unit to look for the problem, eventually I fitted all RCBO's and once proved to be a problem on the kitchen circuit used plug in RCD's on appliances.

 

[ericmark]

The earth - neutral leakage is normally zero when no items being used as earth back at sub station is bonded to neutral, but as the power uses increases the neutral voltage starts to climb towards line, as this happens any connection between earth and neutral will carry more current, so a bit of damp toast in toaster may not trip the RCD even when toaster switched on, but when kettle which uses more current to toaster is used this means neutral goes further towards line, so now enough current flows, so a fault in the toaster trips the RCD when kettle is used.

The dish washer once the heater is used is using a lot of power, they start off washing cold to wash off egg etc, then part way through wash start to heat water. When the heater cuts in it could be the heater down to earth or could simply be because there is a higher load.

Most appliances switch only the line, the neutral is not switched, so step one is unplug anything not in use, the PAT tester often does not run the device for long enough for the heater to switch on, so insulation tester between earth an neutral is often a better test.

But I am an electrician, so I have an insulation tester which uses 500 volt to high light problems, for the DIY to detect the fault is not so easy. If you have two RCD's or more, then using an extension test only and taking supply from another RCD can show if dishwasher at fault, the extension must be 13 amp rated and be fully unreeled.

Where only one RCD in the house more of a problem.

Again my house has all RCBO's which is a RCD and MCB combined so easy to try on another circuit.

My guess and clearly can only guess, the leak has caused a neutral to earth leak, and the dish washer is big enough to lift neutral voltage enough towards line for it to trip. This is why I said try kettle in same socket, if kettle trips the RCD as well then neutral - earth fault, if it does not then likely a dish washer fault.

 

[SUNRAY]

This is why I said try kettle in same socket, if kettle trips the RCD as well then neutral - earth fault, if it does not then likely a dish washer fault.

He's already tried that one and seems to be all over the suggestions

I did plug a kettle into the dishwasher plug and boiled a few times to see if it would trip, but nothing. My next troubleshooting job will be to pull the dishwasher out and plug into another wall socket and run, to rule out if it's definitely not the dishwasher.

Hopefully the extension will offer some insight.