Horstmann Economy 7 quartz not heating on timer

[John Kinsley]

I have a Horstmann Economy 7 quartz controller fitted to a Kingspan Range Tribune HW tank. Both are relatively new (4 years old). For no apparent reason the hot water has stopped heating up overnight.
The boost setting still works, and the 'timed' light comes on on the controller when it should be heating the water overnight, but the water isn't getting heated on the timed setting.
Any ideas what the issue might be?

 

[JohnD]

if the "timed" light comes on, the supply circuit and the timer appear to be working, so it may be your immersion element or thermostat at fault. A wiring or connection fault is less likely unless they have been tinkered with or damaged.

Have you got a multimeter?

 

[oldbuffer]

1. Modern immersion heaters have an overheat thermostat fitted. This cuts the electricity off to the heater if the temperature goes over a specified value, usually around 85 degrees. These thermostats do not reset themselves. You have to push in a small button, sometimes a concealed one which needs a paperclip or similar to operate.
2. If the overheat thermostat has gone on the overnight immersion heater, you may be able to reset it as above. However, be aware that you may have to remove the cover of the heater, which exposes terminals at mains voltage. Make sure the power is off, including any economy tariff power.
3. If you have two immersion heaters fitted, the lower one is normally on an economy tariff, and will heat the whole tank at night. The upper one will be the one operated by the boost control.
4. A photograph of the cylinder, immersion heater(s) and controls would help if you need further advice.

 

[John Kinsley]

Thanks for replies.
John D - I'm afraid I don't have a multimeter.
Oldbuffer - I've attached some photos - there don't appear to be any obvious reset buttons...

 

[oldbuffer]

1. You have to remove the black circular covers from the heaters to see the reset button, hence the warning about exposed terminals and mains voltage.
2. Isolate power, both standard and economy tariff.
3. Undo small nut, remove cover.
4. Reset as appropriate, replace cover, do up nut reasonably tight so children can't undo it, power back on.
5. The economy tariff (if any) will almost certainly power the lower immersion, heating up the whole tank overnight on cheap rate. There will only be power on this circuit at preset hours, normally around midnight to 5 am. However, there are different tariffs with different hours, so the time of day must not be used to assume no power.
6. The top immersion will be on the standard tariff and will boost the top third of the tank if you run out of hot water.

 

[John Kinsley]

That’s all working now. Thanks for your help!