That must be it, right? Fingers crossed. But leak, or condensation?

[happysteve]

A few weeks ago I posted this in another thread...:

My job this morning was looking at a similar circumstance, for one of my regulars, unfortunately the power tripped while they were away and they lost everything in their fridge and freezer - one out of 2 RCDs tripped. They have a fancy alarm and it sent them a text message when the power failed, just after 1am last Wednesday morning (not that they did anything with this information!). Checking historical weather, not partifularly wet either at that time or just before. 2x exterior lights bone dry (though one quite old). Global IR (L+N) to E @ 250V = 5.39MΩ. Ramp test 27mA (slightly higher than usual, but fine). Trip times all good, no trip on 0.5I∆n. Measured leakage by clamping L+N tails together: total on the non-tripping RCD was 2.8mA, total on the RCD that had tripped = 6.7mA.... this did jump a bit by 3-4mA as circuits were energised. I don't have a high degree of confidence in the leakage reading, I suspect it's scaling with current consumed, rather than being a true measure of leakage.

They are going to get a board change in the new year, pricing up a Fusebox SPD RCBO board (usually fit Wylex but 12 circuits so £££). In the meantime I told them to give me a ring if it happens again (though preferably not at 1am!)

The tripping kept occurring, so I went back and moved a likely candidate circuit to the other RCD to see if the problem would stick or twist (I also repeated all the dead tests and leakage, all still good at time of testing). The problem moved! So we narrowed it down to 1 circuit, "house sockets", a RFC serving most of (but not all) the house. Crucially, on that circuit, no outside lights/sockets, no boiler.

More tripping, almost always in the early hours of the morning. Nothing extra on in the night (e.g. dishwasher, washing machine etc). Trips when they're in bed, so not likely a loose board pinching a cable when they get up to use the bathroom.

Asked them to plug the fridge-freezer into another circuit (on the other RCD) via extension lead. Same RCD tripped, so fridge-freezer is in the clear.

With 3 generations of the family incoming for the Christmas period, they're getting a bit desperate so I agreed to bring forward the board change. Doing my pre-board change checks this morning, paying particular attention to the problem circuit. Went round every single socket....

... and when I unscrewed the 2G USB socket next to the fridge-freezer, water started dripping out. Metal back box wet at the top, water definitely inside the plastic casing that houses the USB gubbins.

That must be it, right?!? Please, please let that be it!

Question is... leak or condensation?

Now, there is a bath above, and also, it's a fancy fridge so there's a pipe coming down to feed the ice-maker. However, both bone dry (under the bath and the feed pipe for the fridge).

Wall is exterior, and feels very cold to the touch. Fridge-freezer mounted very close to the wall. Socket right next to where the fridge-freezer sits. Evidence of moisture in the wall (bubbling plaster/paint, plus wet back box).

So I'm thinking condensation? Wall gets colder at night, heat from the back of the fridge-freezer causing it... maybe? If so... how would they fix it? We pulled the fridge-freezer a bit away from the wall

Fingers crossed that's nailed it - temporarily terminated the cables that fed the USB socket in a JB and moved it away from the wall, so shouldn't get wet. Bit reluctant to put a socket on until the water problem is fixed.

Place bets now! I'll let you know tomorrow.

Sorry for the ramble, it's been doing me 'ead in!

 

[brianmoooore]

If it's condensation, then a surface box is the answer, although this could be a problem if it's directly behind the fridge.
Last tripping RCD fault I had below a bathroom was caused by small leak from a shower. There was no evidence f the leak on the ceiling, and dry under the floor by the shower as well. The drips were falling into a 20mm round conduit, which went down to an IP55 light switch in a storage room, which was part of the house, but accessed from the garden. Removed the face of the switch, and it was half full of water.
The conduit projected up into the ceiling void by a couple of inches, so it wasn't water running across the top of the ceiling into it.

 

[happysteve]

Result!

Steve does a happy dance