Danfoss TS715SI not working?

I’ll give that a go when I get home, thank you. It does seem too much of a coincidence. I’ll let you know if that works!
The neon in your pic is on when the switch is off , if that goes out when you seperate the wires on the lighting circuit , than that is where the problem is, if your programmer doesnt come back on you have damaged it, that neon light should not be on when the switch is in the off position
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Yes, you mean the red light next to the water heater switch? I thought so, which is what’s confused me a little.
Wires isolated with light down, but the red light remains lit on the hot water heater switch when off and still no display on either the Danfoss or thermostat fitted to the cylinder.


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With the pic of your wires at the ceiling rose you cant get that wrong they can go either way round wont make any difference, some lighting rose have many wires going in but yours is a simple spur , so that hasnt caused the problem you are having, can you post a pic of your consumer unit/fuse box so we can see what your setup is
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Sure, here you go. I’ve checked this, but nothing obviously wrong. You can see the hot water.


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No but I’m going to buy a multimeter and test the wires to the thermostat
You could also test the wires going to the mv between brown and blue or earth and should be 240vac with a hot water demand.

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