Hot water tank not keeping heat

Section62

Bendy_House said:

ForestBluebells said:

I’ll leave it a bit longer and see if it still heats more otherwise I’ll try the “on” switch on the side

Cool. That'll be interesting.

Lovely and hot, hopefully.

ForestBluebells

Ok this isn’t going well. On Saturday I had a shower in the afternoon as I’d been for a run, hot tap only and it was warm but not hot, Sunday I got up an hour earlier than usual and the water was hot! Needed cold tap too! Both have had water heating for full recommended 90 minutes. 

I upped it to 2 hours and this morning the water was so cold I couldn’t shower 🤷‍♀️

Bendy_House

ForestBluebells said:

Ok this isn’t going well. On Saturday I had a shower in the afternoon as I’d been for a run, hot tap only and it was warm but not hot, Sunday I got up an hour earlier than usual and the water was hot! Needed cold tap too! Both have had water heating for full recommended 90 minutes. 

I upped it to 2 hours and this morning the water was so cold I couldn’t shower 🤷‍♀️

Blimey.

Could you please try - turn off the timer overnight so it just doesn't heat up the hot water at all. Then, as soon as you get up, turn it on (using the override switch) for 45 minutes. After 45 minutes, check the water temp, and then check it again several hours later.

Ie - cut out the 'overnight' malarkey, and just test whether the actual immersion heater is doing its job.

ForestBluebells

I just accidentally had the override on for over 2 hours and it’s only slightly warm 

Bendy_House

In that case, there must either be an issue with the 'timing' beyond/before the analogue timer - ie the 'smart' setup is preventing the immersion from being supplied (which would seem crazy) - or there's a presumably-intermittent fault with the immersion element, or in the supply to it.

This could include the override switch, as this is (almost certainly) the same switch that's operated by the actual revolving clock - and that still doesn't look quite right to me. If that override switch - effectively a microswitch - has scorched contacts, then that can lead to intermittent behaviour.

I think we may be at 'sparky' stage?

ForestBluebells

I think So too, if it’s not hot after 2 hours heating in day time using the override something has gone wrong somehow. I’ll contact an electrician 

Section62

ForestBluebells said:

I think So too, if it’s not hot after 2 hours heating in day time using the override something has gone wrong somehow. I’ll contact an electrician 

Yes, having ruled out the timer not switching the element on for long enough, I would stick with my suggestion of the thermostat being iffy.

Replacing the thermostat is potentially a DIY job, but it would be sensible to get an electrician to do it and then give the water heater electrics a check over to make sure there is nothing else wrong. (I'd change the thermostat regardless as it eliminates one of the possible 'intermittent' causes of fault)

coffeehound

@ForestBluebells  Did you check whether any water was being discharged through the tundish when the immersion was heating?

ForestBluebells

I forgot, I’ve turned it back on to check. Interestingly it’s making a knocking noise

ForestBluebells

No obvious leak but water is slightly hotter although not “hot” I used to not be able to stick my hand under the hot tap without using cold too so that was just a nice warm but not hot