Two trips in two days

[Fordy81]

Before I call a sparky out, can anyone offer any advice?

So yesterday I got home and the kitchen circuit breaker had tripped. Partner and kids home but none of them even realised so were no help in identifying what might have caused it (ie any switches being turned on off etc).

This morning, I turned the dishwasher off at the fused switch on the wall, and the mains switch tripped so everything went off.

Reset it, and turned the dishwasher on and off at the wall and was absolutely fine.

Anyone with any ideas?

Thanks

 

[Notch7]

I saw the thread and thought you might be trying out some magic mushrooms

 

[Fordy81]

I saw the thread and thought you might be trying out some magic mushrooms

Sadly not. But we do have some fungi growing in the garden so if it’s an expensive fix that will at least soften the blow!

 

[CBW]

Is it an mcb that’s tripping or an rcd? If you’re unsure of the difference post a photo of consumer unit and indicate which one is tripping off.

 

[Fordy81]

So yesterday it was the kitchen MCB that tripped. Today was the mains one on the right (RCD?)

 

[CBW]

So yesterday it was the kitchen MCB that tripped. Today was the mains one on the right (RCD?)

So given that, I’d be looking for an Earth or neutral fault, possibly on the dishwasher?

 

[ericmark]

With 7 MCB's on one 30 mA RCD suprised the RCD does not this more. The MCB tripping is more of a concern, but depends what was running.

 

[Fordy81]

With 7 MCB's on one 30 mA RCD suprised the RCD does not this more. The MCB tripping is more of a concern, but depends what was running.

Sorry do you mind expanding? Do you mean the consumer unit needs upgrading?

To be honest I don’t think any of the big appliances were running. Certainly not washer, dryer, dishwasher, just fridge/freezer. If anything I imagine it would have been kettle or microwave but as I wasn’t in my daughter and partner are of no help in finding out what was on!

 

[Fordy81]

So given that, I’d be looking for an Earth or neutral fault, possibly on the dishwasher?

Would that just be the wiring on the socket and/or fused switch?

My partner has said that the washing machine has tripped something in the past but not for a long time (maybe a year). She can’t remember whether it was the MCB or RCD. That’s on the same wall as the dishwasher.

 

[terryplumb]

The MCB tripping is more of an issue . That trips due to excessive current ( over and above it's rating) ,such as a short circuit or an overload.

 

[winston1]

This morning, I turned the dishwasher off at the fused switch on the wall, and the mains switch tripped so everything went off.

Doesn’t solve your problem but there is no need to do that. The dishwasher will have its own switch.

 

[securespark]

It is highly unlikely the appliance switch will be double pole, whereas the Fused Connection Unit, if fitted, will completely isolate the appliance and help with fault-finding.

 

[ericmark]

My house putting a clamp on ammeter across both the DNO tails I measure around 18 mA, not enough to trip an RCD but well over the recomended 9 mA if I have any items leaking around 9 mA with a single RCD it would trip.

So I have 14 RCD's which are combined with my MCB's the combined unit is called a RCBO.

When the RCD first came out in domestic installations we used 100 mA models, often with delayed tripping, (S type) but one could still get a nasty shock, so we moved to 30 mA, but to stop nuisance tripping we split the distribution box, some times with only sockets protected, other times using two RCD's and then into 3 with so many items on each of two RCD's and are some items either MCB only or RCBO's.

As the price of RCBO's dropped, we moved in the main to all RCBO's but nothing to stop cheap skates sticking with either one or two RCD's, but of course one has to expect it to trip every so often.

When I came to do this house, I decided if I loose the contents of a freezer it will cost more than the extra to fit an all RCBO consumer unit (type tested distribution unit) cost about £200 more, and no one forced me to buy one, but it made sense.

At the same time I upgrades to 100 amp so if I decided to go for electric heating or electric vehicle I can, and also added a surge protection device.

But all this does not help when a MCB trips, a ring final is normally 30 or 32 amp, and can feed loads of 13 amp sockets, so easy to overload, so the IET recomend any non portable appliances (portable under 14 kg or on wheels) using more than 2 kW should have a dedicated supply.

In real terms we do have a dedicated supply for the immersion heater, but the tumble drier, or washer drier which are likely the next most likely to overload the circuit.

The cooker is normally over 13 amp, so normally a dedicated circuit, but as the eye level oven came in, we started to plug them in, my own house I have two kettles 13 amp each to speed up making coffee, only on for 45 and 60 seconds, but still an overload. And often we do overload a circuit for a very short time and get away with it.

But you need to add up what you have 230 watt = 1 amp.

 

[SUNRAY]

It is highly unlikely the appliance switch will be double pole,

Or even have a proper mains switch... winston has been told this frequently

whereas the Fused Connection Unit, if fitted, will completely isolate the appliance and help with fault-finding.

My hunch is faulty mains filter in a white appliance dishwasher or washing machine, they are notorious for causing this problem.
The fact it happened as the appliance was switched off I'd say it's a good starting place.

 

[flameport]

Sorry do you mind expanding? Do you mean the consumer unit needs upgrading?

Many items of equipment have a small amount of leakage current in normal use.
That RCD is rated 30mA, and the maximum allowed current in normal use is 9mA, which divided across 7 circuits is only just over 1mA per circuit.
Above 9mA random tripping is possible.

Having the entire installation on a single RCD was never valid.
The RCD you have got is obsolete - BS4293 was replaced by BS61008 in 1990, 4293 was eventually withdrawn in 2009.
A replacement consumer unit would have individual RCBOs, so any fault would disconnect a single circuit only.

The dishwasher may have a fault, or there may be one or more faults between N&E elsewhere on that circuit or other circuits which only shows up as a trip when a certain combination of loads is connected and switched on.