Immersion heater fault (edited)

[Jean THT]

i will postulate that your timer is by the meter, and that you have two cables from the meter(s) to your two consumer units, and that the off-peak consumer unit will (should) probably be timed to come on overnight. The upper immersion heater supply will be live 24 hours, subject to your local switch.

That makes sense. There are two switches, and on one of them, the red neon light was off, and the immersion heater did not work. I thought i had done things incorrectly but if the electricity only flows at midnight, then the neon light will turn on later tonight and the bottom heater should start working.

Is your tapwater scalding in the mornings?

No, it isn't scalding but it may be less hot in the evenings now you mention it

 

[winston1]

Right, so I've got two new plugs to replace those ones, which had dead neons:

View attachment 139062

A plug is the "thing" on the end of a lead with pins on it. Neither of those two pictures are plugs or even sockets. The left one is a switched fuse connection unit with a neon, the right one is a switch with a neon.

Frankly you don't need the neons, they just waste electricity.

 

[Jean THT]

good point, let me edit that for clarity.

I actually like neons, especially since one of the switches is only active at night, it's useful to know when it's on.

 

[Jean THT]

And to conclude here, the problem was that the immersion heater tripped and pushing back the button solved it. Thanks so much for the help finding out, I'd have never found this on my own!

I'm going to keep an eye out for further issues, it could be a sign that one or both of the immersion heaters are close to the end (they've been installed in 1998).

 

[stem]

The trip button is there as a safety device, to stop the water getting too hot or even boiling and scalding the user. If there is a fault with the thermostat, you might find it will trip again. Hopefully not.

Older immersion heaters don't have this safety facility and as immersion heaters are usually identical models when installed and yours are different I suspect that one of them, the one with the 'trip' may have been replaced already, or at least its thermostat has. This would make sense as the 'off peak' element normally does get the most use.

As you weren't able to get any hot water at all when the 'off peak' immersion had tripped, that suggests that the other 'daytime boost' immersion (assuming that you tried switching it on of course) isn't working. This heater should be able to heat the water at any time.

 

[Jean THT]

Thanks, stem.

As you weren't able to get any hot water at all when the 'off peak' immersion had tripped, that suggests that the other 'daytime boost' immersion (assuming that you tried switching it on of course) isn't working. This heater should be able to heat the water at any time.

I think that the thermostat with the trip was actually the daytime one, as it started working after I pushed it back, and it was 19:30.
It's possible that the off-peak immersion wasn't working because of a defect in the switch (which I replaced). Now both seem to be working fine though I've turned off the daytime one to test that water indeed gets warmed-up at off-peak time.