Out of interest, how would you desolder a multiple pin component? I’ve seen a couple of methods but just wondering what you'd do.
Looks like there is a coating on the board..
That’s probably what caused you some grief..
I was checking the other day, de-soldering stations have come way down in price..
On the board, find the coil connections for the relay and trace them back..
One will go to ground, the other maybe a transistor driving it..
but does sound like it’s what ever circuit is driving the relay is what is shorted..
I would also contact the eom and see how much a replacement board is..
good luck.. ~q
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Liquid flux, hot air gun, medium tip, HOT but med low air flow. Before starting use something like forceps to grasp whatever it is you are desoldering and apply just enough 'pull' so when the solder melts it comes out quickly. Use solder wick to clean up the area afterward.
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Thank you I'll try all of that.
I have already enquired and they only sell the complete unit at a price of £440!!! That includes everything including a heater… which I don’t even need. Is why I have decided to try and fix the problem myself.
There was indeed some sort of coating on the soldered areas as it wasn't conducting with the pins. A bit of heat and it scrapped away on the areas I needed to unsolder but is there another way of removing this coating?
also what would you suggest using as I'll obviously wanted to re-protect it after I've finished. Is there anything specific to use? I do have liquid electrical insulation paste?
Hi, @Stevelondon
You need to find someone with an appliance tester.
To measure earth circuit, insulation and leakage current.
That will show you where the tripping could be.
You need some high voltage insulation test equipment and someone who knows how to use it.
Tom.... 
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Ok so damn. Just got in and measured across the MOV and it’s OL so it looks like it’s not that. Was hoping that would be an easy fix.
- is there any way of testing the relays for shorts to earth if they’re not energised? (Bare in mind it only trips when they’re energised and turn the pump on)
- Can anyone see any other potential culprit that might trigger this trip ONLY when the pump circuit goes active?
Just ordered myself a hot air gun and liquid flux. Getting into this now. Probably won’t ever use it after this. 
So did you test it with pump completely disconnected from the board?
Also, you didn't post anything about the RCD, some of them have also circuit breaker built in.
Yes completely disconnected. Absolutely every wire disconnected apart from the mains in and the control panel (3 wires, 12v+, 12v- and signal) so no loads what so ever.
my initial suspicions was the pump because I know they can burn out if there is an airlock, however now I am thinking it is either something that is burnt out because the pump was drawing excess current from being run semi dry, or something has gone because of the turning off and turning on again a few times.
there is no built in RCD as far as I'm aware. It is literally plug→cable→PCB
I mean, the RCD that trips. Some have CB as well, so they can trip from over current (short) as well.
Ahhh I get you. Normally when I go over current (hot tub running and fire up my table saw) it just trips that breaker. However this is doing it even with no loads so I am assuming it has to be a live or neutral to earth short somewhere.
Ok.
You are assuming correctly, if that tripping RCD is for your whole house. I didn't have enough info to exclude possibility that the RCD was installed only for hot tub.
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Yes it is for the whole house.
I have just checked the MOV again with the following results all on 2Megohm setting
MOV1P - 1-1→OL
Thermistor 10.5 ohms
The two lower Y capacitors are straight to OL which my material says is an open circuit and not good. 
The ceramic capacitor shows 0.5→OL
The usual way of checking an RCD in a domestic situation is to isolate everything on the circuit and see if the trip resets.
Most consumer unit RCDs will have a main switch and test button. In a no fault condition, the main switch will latch in the ON position and release with the test button.
If that's OK, you keep adding items on the circuit until something trips it. Water or damp accounts for many of the trips, kettles etc.
I don't know if you can do the same with your setup. I have tested RCDs in the past with a suitable resistor, but now use an installation tester which tests for the correct trip current (e.g. 30-mA) and time (e.g. 300-mS) at 240-V.
I don't know offhand how hot tubs are classed safety wise, but probably Zone 0.
Be aware that Circuit Breakers (CB) are different devices. CBs can be chosen for specific tasks. In the UK, type B is commonly used. Type C is designed to deal with surges, a bit like fast acting (F) fuses or surge tolerant (T) types.
Thank you for this but I know what device is causing the RCD to trip, it's now finding the faulty component(s) on the board.
Even if you know that this device is "causing" the trip, the whole picture can be different.
In many cases what causes the trip is just a cherry of the cake. Your RCD can trip anywhere between 20mA and 30mA.
Let's say you have laundry machine that has significant leak of 20mA.. Now any insignificant leak could make RCD to trip.
not exactly sure what was used..
but do a quick search on conformal coating and pick up a can..
good luck.. ~q
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The process on the board is the same as finding the damp kettle, but more difficult.
You could start at the mains section of the board and isolate that, maybe snip the transformer LV side leads. Check the earth/live/neutral tracks for defects.
If it goes beyond the HV side, then that's going to be a challenge.
The RCD primarily looks for imbalances in the live and neutral paths, but can trip on overload.
If you have a bench power supply, you could try powering the board separately from the transformer.
You'll have to be careful not to zap the board.
I understand. I do actually have a fish tank with an earth rod (going to a plug) for stray voltage from the equipment in there so that might be what helps cause the main RCD to trip as you say. But to test around that I bought a plug in RCD and plugged the hot tub directly into that and that tripped also so the leak from the hot tub itself must be >30mA (rating of the plug RCD)
I’ve looked everywhere I can think of on the board and can only see earth tracks shown in red below and not to any other components so I can't see where a live/neutral to earth short could even take place.
Wondering on your thoughts if it could be a live/neutral imbalance that’s causing the trip instead of a short to earth? 
