Immersion heater problem? Or could be shore power problem?

[Cardo]

We've been plugged into shore power for the last 24+ hours and have just discovered we have no hot water. The immersion heater, powered from shore power was working fine last time we used it, as far as I'm aware. However, now all we get from the hot water tap is water that's a tad warmer than the stuff out of the regular water tank.

Upon checking the shore power breakers I've discovered that our polarity checker (we have a box with green and red lights, a buzzer and a switch. If the shore power supply is connected up the wrong way round the red light and buzzer come on and we just flip the switch to fix it) has the green light on, however there is a dim flicker on the red light and there's a very faint buzzing. I noticed this a few days back at a different location when the shore power lead hadn't been plugged in properly. Removing it and replacing it sorted the problem. However, I have tried that this time, and I have also plugged the shore power lead into four different outlets (in the same box, mind) with the same result.

All other shore power appliances seem to be working fine.

So, two (or four) questions:

1) Could this odd polarity thing be causing a problem with our immersion heater? Or is it buggered?

2) What could be causing the polarity checker to get upset? And should I remove the shore power before something (else) breaks?

 

[nigelmercier]

Difficult to say without knowing what the tester is indicating, but try boiling an electric kettle; if it boils, the power is OK for the immersion heater.

If the immersion heater is not working, it could just be the thermostat. Before you leave the boat, get your hot water tank model and dimensions, and the details of the old heater element and thermostat. Take pictures, and measure the thread on the tank. I had to do this by remote control!

 

[Cardo]

Well, it wasn't anything to do with the shore power.

I managed to pull out the calorifier from its unaccessible spot (who on Earth put it there?!) so I could get to the immersion heater on the top. Turns out the overheat trip had gone. I think it may have happened after a long day of motoring in hot weather where the engine had heated up a tad after the water inlet blocked (yet again!). We likely plugged in before the water in the calorifer had a chance to cool so it tripped straight away (at 80ºC).
Reset and working fine now.

 

[Mrnotming]

This happens to our Nautic Boiler as well, but only if the ship's water tanks are allowed to run dry.Then the dreaded click occurs and it's time to go poking with a cocktail stick at the reset button , which of course is sandwiched between the hull side and the calorifier!
Glad you sussed it yourself!