Heatwise - Hot water only on boost

[DoomSprout]

Hi,

We are on Eon's Heatwise plan, where we have a gas boiler for central heating, but our water is heated solely by an immersion heater.

Lately, we keep finding we have no hot water. If I press the boost button on the electricity meter, the water heater kicks in and the water heats up. I replaced the cylinder thermostat a couple of days ago in case that was playing up, but today we have no hot water again.

I'm not sure what to look at next. Is it possible the Heatwise meter is playing up and not turning the supply to the heater on overnight (so I need to call Eon), or could it be something else (so I need to call a plumber)?

I'm planning on staying up late enough tonight that I can check whether or not the heater starts by itself without me pressing the boost, but is there anything else I should be checking?

Thanks for any advice,

Alan

 

[DoomSprout]

Bit of extra info - the isolation switch seems to be dodgy. The switch is difficult to press, and doesn't fully click into the 'Off' position. I'm going to replace this tomorrow as I'm not happy with it. I'm hoping the whole problem might turn out to be as simple as a faulty switch.