I used to use these forums a lot a while ago as I started my Arduino adventure and although this isn’t Arduino related, I haven’t found a forum with more clued up people so though I would try yourselves for help.
I have a hot tub which has started to trip the RCD on the main fuse board.
Cause: I was turning the pump on and off every 10 seconds or so to get rid of an airlock and then all of a sudden it tripped the RCD and hasn't been right since.
diagnostics: after a lot of playing with it I have found the following.
it trips even when no load is connected. ie no pump, no heater, no ozone etc so I have discounted an issue with those parts.
It only seems to happen when the pump turns on. (Or should turn on if connected)
I have removed the pump Live relay to see if that was shorting somehow to earth but it is still doing it even with the relay removed.
When I put my MM from Pump Live to Earth, is shows a quick spike to voltage as the pump is called to turn on (I am assuming this is causing the trip. However even with that relay removed, it's still doing it.
As far as I am aware, there is nothing else that should turn on other than the pump when it is called for so can't imagine it being any other relays.
Is there anything else I can do to diagnose the issue that you can think of?
Can you see anything else on the board that might be able to trip the RCD
You could try https://forum.allaboutcircuits.com/ There are many very experienced and helpful people over there. I’m not suggesting the people on this forum aren’t both experienced and helpful, but that other forum is more oriented to electronics issues.
If the RCD trips it means one of two things. The RCD could be bad. Replace it and see if that is the fix. If not, you need to find where your hot line is touching earth/ground.
I thought it might have been the pump relay but not quite having much knowledge to test it properly I tested all 6 legs and none went to earth. But wasn’t sure if it might when it is energised. Which I can't do with the board out of the unit and unpowered, but if it was powered it would instantly trip and wouldn’t be able to test it.
I removed the relay completely from the board (the one missing in the image) but it still trips the RCD so can’t have been that.
Play with your multimeter, all circuit disconnected, and measure resistances between earth(G) and the rest. If there is Line-to-Ground MOV (the blue guy), that would be first candidate.
I'll check the MOV when I get home. Haven’t checked that one yet. Wish I had before spending ours trying to get that relay off. Took me forever as didn’t gave a decent soldering iron.
I've only ever used continuity to check it, what kind of resistance values should I get if it is shorting to the earth?
Also (not knowing exactly what the MOV is or does) is it possible that it would only ‘go wrong’ upon activation of the pump?
Based on your recent comments and the fact that you are dealing with 240VAC, you should at least seek the assistance of an experienced hobbyist or professional help. Soldering that relay back on with an inadequate soldering iron could either damage it or cause it to malfunction with unknown repercussions. Since you don;t know what a MOV is and it's importance to this product and to your problem then this is a BIG warning for you. Good luck.
I do get what you're saying, I just didn't have an adjustable iron which I have bought now and it wasn’t getting hot enough to desolder the joints. I always try and learn and do everything first and if I don't feel it's safe or can’t fathom it I'll get professional help.
I use liquid flux, it speeds up soldering by at least 100%, temperature is 700F/370C but the real secret is the wedge tip NOT the common conical, much more heat transfer surface with the wedge.
That’s the problem I was having. I’m not sure if different solder has different melting points but I tried all the way up to 500c with the wedge tip and were even marking it. Had to swap to a point tip to get it to start melting. I only have a more denser flux paste but gonna grab a tube of the more fluid stuff.
Managed to get it relatively clean though with the sucker and solder wick. Need to find the actually cause now though but will test the MOV on the morning.
