Horstmann Electronic 7 - timer always on

[andy118]

Started having an issue after the electric tripped where the timer is always on and the display has frozen. I've read the newer model can be reset with pressing all the buttons but this doesn't seem to work. Turning off the circuit hasn't worked either. Could this model be upgraded and would it fix the issue?
Thanks

 

[Murdochcat]

Turn off the circuit at the fuseboard for a few minutes

 

[andy118]

Left it off for over 20 minutes and no change.

 

[RandomGrinch]

As you say, from the manual, you should be able to reset from the button presses...

Although it doesn't mention it, the diagram does show the slide switch in the manual boost position, may not make any difference, but could be worth a try!

Other than that, the programming is backed up by a battery on the PCB. If you have any competence in electronics, this can be desoldered/disconnected to 'hard reset' the device (take it off the wall, and completely remove it from the supply, before attempting disassembly!).

 

[andy118]

Thanks, I have a manual but it doesn't mention this reset so not sure if it's a slightly different model. I set the switch to the one hour boost on the far right and pressed the buttons but still no change.

I'm ultimately wanting to replace the existing immersion heater with a dual heater as I've got an old copper tank and just want to partially heat this. Not sure if this can be done while this isn't working properly.

 

[RandomGrinch]

I'm ultimately wanting to replace the existing immersion heater with a dual heater as I've got an old copper tank and just want to partially heat this. Not sure if this can be done while this isn't working properly.

The Horstmann is only a glorified switch.
If you have a main switch for the immersion, in addition to the Horstmann, you may be able to bridge it out.
For a short term solution, you could then simply switch the immersion on and off, from the main switch, when required.

If you are happy to, post a picture of the wiring behind the Horstmann, and we may be able to advise.
You never know, with the unit removed from the wall, you may find a reset switch on the back!

Alternatively, just buy a new one...

https://www.amazon.co.uk/Horstmann-Electronic-Water-Heater-Multi/dp/B0031SCQMI

 

[andy118]

I suppose a basic timer could do the trick. It's no longer an economy 7 tariff but would rather it only on part of the day. Would you need to see the entire unit off? Here's it without the face plate.

 

[RandomGrinch]

I suppose a basic timer could do the trick. It's no longer an economy 7 tariff but would rather it only on part of the day

Ok, so excluding the earth connection, it's a simple two wires in and two wires out.
L on terminal 1, N on 2, N out on 3 and L out on 5.
Terminal 4 would be a connection to a boost immersion, or can be linked to terminal 5, to offer the boost function on a single immersion cylinder.

Your options depend on the functionality you desire and what you want to spend.

The most straightforward, but pricier option, is to replace with another Horstmann, as in the previous link - this has the benefit of a straight swap, using the original backplate, and the option to use a boost (dual) immersion (as you mentioned earlier).

Otherwise, the cheaper choice would be a standard immersion timer (as no need for economy 7) i.e.

24hr / 7 Day Immersion Heater Timers

Smart immersion timers are available from the likes of Amazon, but then it may be pot luck whether you get a decent one, with their off-brands.

Or the cheapest option, persist with investigations into your original Horstmann, take off the back cover and see what the battery looks like...

 

[andy118]

Thanks, that's really useful. Ideally after the cheapest to run, it's hot water for 2 sinks and a bath which is rarely used. I suggested under sink heaters to a plumber but told this would be much more complicated and expensive. I'll probably go with a newer horstmann timer for simplicity.

 

[Murdochcat]

I would be careful about spending too much to “save” money.

With 1 person in our house and the boiler off, it take about 2 kWh of PV per day to reheat the tank - so that’s washing up, washing hands and a long hot shower covered