So this is where I’ve got to… Suggestions / alternative thoughts would be much appreciated…
Small kitchen in a Victorian terrace. Along the external wall we have the washing machine and dishwasher. These have sockets below the worktop and a fuse switch above the worktop.

Yesterday the power started tripping in the kitchen. By a process of elimination we worked out that if the fuse switch to the dishwasher was off then the problem was “solved”. So pulled out the washing machine and dishwasher and found the beginnings of some black spot mould on the external wall. Whipped off the socket covers and there’s the start of some corrosion inside the backboxes around the earth connection and sides of the box… This applies to both the sockets above and below the worktop.

My thoughts are that we’ve a lack of ventilation behind the washing machine and dishwasher and that we’re getting condensation on the cold external wall. This is causing the mould. I’m also thinking that we’re getting condensation in the backboxes which is causing the corrosion in there. So, solution 1 would appear to be to increase the ventilation behind the a Planes by adding some vents to the plinth, and worse case maybe even an airbrick to the back wall to allow direct ventilation (although I’d rather not do this just yet). However, does anyone think this would also address condensation in the back boxes or are these a bigger problem with being chased into a cold (and pos damp) crappy Victorian brick wall. In addition, a proper extractor fan rather than relying on the trickle vents and remembering to open the window is starting to seem like one of those daft omissions…

Any other thoughts / electricians who have come across corroded backboxes before and might know of anything else to consider? Plastic backboxes a possibility / sensible idea?

Thanks in advance!

Is it a washer/dryer? maybe moist air escaping from the dryer mechanism causing the condensation?

Yes washer/dryer of the condensing type so quite possibly adding to the issue back there.

Shouldn’t have poked around, now tripping the kitchen ring no matter what’s on/off. Calling a trusted electrician tomorrow. The earth connections to the back boxes below the worktop look like they’ve just been raised from the ocean!

Corrosion in me backboxes

I’ve had plenty of occasions when rusty water has spilt out of my backbox. It invariably resolves itself after a day or so.

But I bet it never led to tripping out….

Led to slipping over, which is almost the same.

Yes washer/dryer of the condensing type so quite possibly adding to the causing the issue back there.

Not had one before – are they renound for heating up / leaking and causing condensation? We barely ever use the dryer, but guess it’s still going to get hot back there when washing…

When was it last rewired?

Only asking as i spent ages pondering over tripping electrics and corrosion and it turned out to be that for a few years in the 60s a poor plasticiser was used which leeches out and runs down the wire bringing green gunk with it. Turned out the damp and tripping electrics were separate problems as well.

Annoyingly it was re-wired this time last year as part of a kitchen refit and not had any problems till this. I’m blaming it on the wife who over breakfast thought it was a good idea to reminisce about how this time last year we didn’t have a kitchen and that it was so nice to now have a working one.

Can’t see any green gunk in there, could see some water droplets when I opened them up. Am wondering if we’ve got some rain soaking through the solid wall in the storms but outside looks fine, and the rust suggests this has been a long-time brewing.

More likely related to a problem with the external wall. Poor damp course, or non. Poor pointing. Lime mortar will definitely be porous if its original. If if the wall is exposed I start looking there.
Condensing washer dryers catch almost all of moisture they produce, so I’d doubt its that.