Crossy

Also, is your feed to the pond area underground? Isolate it where it emerges and test (maybe run a temporary above ground feed).

From my earlier post: - I suspect your RCD is right on the brink trip wise, possibly there's a switch-on surge that pushes it over the edge but running on inverter softens that or maybe lack of a N-E bond in the inverter just defeats the RCD for long enough. The above is pure speculation based upon experience, but I really don't know exactly why you are seeing this. So, we just have to use the scatter-gun approach, eliminating the easy stuff first. To actually measure the leakage current requires some specialist equipment (a low reading AC clamp ammeter). You may find that simply swapping the RCD with another will solve the issue. The requirements for an RCD are that they must NOT trip at 50% of the rated current and that the MUST trip at 100% of the rated current. So, a "30mA" RCD could trip anywhere between 15mA and 30mA, a pretty big range. By the way, you really shouldn't be running your inverter with no N-E bond (or at least an earthed neutral - but check the manual) as it defeats downstream RCDs.

Not in this forum but there is an accommodation finding forum. https://aseannow.com/forum/73-thailand-accommodation-finding-forum/

If it's isolated down to the pond the it should be "reasonably" easy. Check everything is dry of course. I've had submersible pumps leak and start tripping the RCD, the only fix then is a new pump I'm afraid.

Oops, sorry about that. I suspect your RCD is right on the brink trip wise, possibly there's a switch-on surge that pushes it over the edge but running on inverter softens that or maybe lack of a N-E bond in the inverter just defeats the RCD for long enough. Is it just one circuit that trips? What's on that circuit?

I really wouldn't be so sure, but let's isolate which circuit has the problem.

RCD problems seem to be en-vogue at present, at least that's one off the list

OK, now it gets harder. Please take great care!! First check with your meter that you have a high resistance between the N bar and the E bar (power off of course) Assuming that's OK. Disconnect about half of the blue wires from the neutral bar and then try the RCD. If it stays on, then connect the blue wires one by one until it doesn't (ideally you should use an insulation tester, but one assumes you don't have one). Otherwise pull the remaining blue wires, hopefully with them all off the RCD stays on. You are trying to isolate which neutral has an issue to earth. So, connect your blues one by one, trying the RCD each time. Hopefully you will end up with one that trips the beast. "All" you have to do then is check that circuit for damp / ants / rat damage etc. .

Unless something is actually fizzing, I doubt there's an issue there (at least not one that would cause your RCD problems). Step by step, no point throwing money at it until we know what's actually wrong.

Well, with that bond the RCD has no chance of remaining on. If you want to implement a MEN system the bond must be between the E bar and the INCOMING neutral (so the blue wire on the main switch). So, for now remove the link so we can see if you still have RCD issues.

Great. I get really worried if I can see bare copper, zooming in I can just make out the covers

Ah, maybe I see it. Is that a green/yellow from the bottom of the N bar round to the E bar? With that link there it's not surprising the RCD won't stay on. Do you have an earth rod?

OK, let me get this right. The large MCCB (the white unit at the top) connects to the incoming supply which is split by those two (lethal, please put the covers on) connector blocks one branch of which feeds your distribution board. Correct? The supply polarity now looks correct, please verify with your neon (should light on the brown wire). With the supply off, please check for a resistance between the N bar (all the blue wires) and the E bar (green/yellow wires), you should see a very high resistance / open circuit there.

The black and grey feeding the bottom of your main breaker are POTENTIALLY the wrong way round going by colour codes (not really a reliable indication but worth investigating). Do you have a multimeter? Or at least a neon-screwdriver? Please tell me you're not swapping the main breaker for the RCD with the supply live.

Better post a photo of your RCD too please. Close enough that we can read the rating text. If it won't stay on even with all the breakers open you very likely have a Neutral-Earth fault, it could still be the damp. Do you have any test gear (multimeter)? Have you verified that there's no damp in the works anywhere? Please also confirm that it has actually been OK in the past. It is looking like you need a sparks with the proper gear (an insulation tester at least) and the knowledge of how to use it. EDIT I'm also looking at your main breaker wiring, if the colour-coding is correct (definitely not a given) you appear to have a reversed L&N.

A Dentist, doing his first extraction on a patient, was understandably nervous. When he got the molar out, his hand shook, he lost his grip on the instrument, and the tooth dropped down into the patient's throat. "Sorry," said the doctor. "You're outside my specialty now. You should see a laryngologist!" By the time the unfortunate victim got to the laryngologist, the tooth had worked its way much further down. The laryngologist examined the man. "Sorry,"said the doctor, "You're outside my specialty now. You should see a gastrologist!" The gastrologist X-rayed the patient. "Sorry," said the doctor, "the tooth has traveled into your lower intestines. You should see an enterologist!'' The enterologist took some X rays. "Sorry, the tooth isn't there. It must have gone down farther. You should see a Proctologist!" The Proctologist examined the patient.... inserted a proctoscope and remarked... "Good heavens, man! You've got a tooth up there! You should see a dentist!"

Rice may attract the ants we also want to avoid.

Hmmm, who installed the RCD? Can you post photos of the board with the lid off please. Are you saying the RCD won't stay on even if all the breakers are off? If that's the case you are probably looking at a neutral to earth fault which can be a nightmare to find. Do check boxes for damp and possible ants.

It definitely sounds like the damp has gotten somewhere it shouldn't. Check that your boxes are completely dry (Madam's hair-dryer) then try to hunt out any other places where the wet could access.

It all the fault of listening to GHR!