Just returned from the boat.
I took with me a circuit tester and checked the cable. All is ok. So that suggested that the problem is on board.
The circuit breaker on the front of the panel has a test button and shows either ON or OFF when tripped. Do these breakers ever malfunction?
I had the shore power plugged in and then turned on the immersion. The red light on the immersion switch didn't illuminate. However, within 10 mins I had piping hot water at the taps. Does this only work when the shore power is connected?
I had taken down a 240v vacuum cleaner and that worked fine from all 240v sockets including the panel. If shore is not connected will these sockets still operate from the batteries/inverter?
Fenders
Hi Fenders,
So the cable is good, and the fact that your 240v vacuum cleaner worked from the 240v power sockets indicates that shore power is getting onboard.
You mentioned that ten minutes after switching on your immersion heater that you had hot water at the taps, but you didn't mention whether you had been running your engine at all. If the engine had been running, it would have provided heat to your calorifier (hot water tank which contains both your 240 volt immersion heater and a heat exchanger powered by your engine fresh water cooling system).
Assuming your engine had not been run prior to checking for hot water, would suggest that your immersion heater is being powered from the shore supplied 240 volt mains. Although it is possible to get a battery powered electric immersion heater, your leisure batteries onboard would not be connected to the immersion heater within your calorifier or hot water tank because the amount of power that heater would take would flatten your batteries very rapidly indeed. So the water heater will only be operable when your boat is connected to shore power, likewise also for your 240 volt power sockets.
The foregoing would therefore suggest that the green shore power connected light is faulty if it does not light up when you are connected, and likewise for the light in the red immersion heater illuminated switch.
In the appropriate circumstances your mains trip switch could malfunction, but usually when that happens it is a one way event in that it used to work, but now it's dead. Whether it could die in the permanently on position I don't know, though I suppose anything is possible.
Did you notice if your battery charger system was working at the time because if you have no indication there either, then it suggests to me that there has been a situation onboard in which each of the power on indicators has been knocked out. That in my opinion is worthy of getting a qualified and competent electrical engineer to take a very close look at to find out what has gone wrong. Good luck!