Yes - the sparky has used 4 core (3 plus earth) when he should have used
5 core (4 + earth). Sparky has sleeved the earth to use as a switched neutral to swap over the sink and bath heating elements. Not a good bit of wiring. Snot
Good question. We have never used it in the 11 years we have lived here. Until that is, last week when a motorised valve failed meaning the gas boiler didn't heat the hot water! I then flicked on both switches and nothing happened. No fizzy noise and no hot water! I replaced the motor and gearbox in the valve next day and only yesterday got around to exploring the failed immersion.
It now seems the immersion does work going by fizzy noise and speeding up of electric meter when "bath" switch is on.
I assumed some dick head had messed with the wiring whilst the house was owned by the local health service, from, whom we bought it. Unless someone here came up with some very good reason for the weird wiring I intend replacing the switch (which by the way is hidden under a shelf in the hot water cylinder cupboard so has never been cleaned) with a nice new single one.
The tank does have provision for a second immersion heater below the one fitted.
Mike
From what can be seen in the pictures, it would seem that it once had a twin element immersion heater fitted to the tank which has now been replaced with the current single element one.
The only reason the fuse / cb in the CU doesn't blow to the full earth on the changeover switch[1] seems to be because it is fed from the neutral coming from the double pole on/off switch.
The original 2 element wiring seems to have been a bodge (using the earth wire as a second switched live in the connecting flex). Assuming the use of high temperature silicone insulated flexible cable that's mandatory for immersion heater connection, the wiring is now correct at the immersion end of the circuit but a complete and utter bodge at the switch box end.
You need to move the red sleeved yel/grn onto the earth terminal (and remove the red sleeving). disconnect the blue switch strap and transfer the immersion cable blue to the terminal on the 2 pole on/off switch marked N from which the strap had been removed. This should leave you with the changeover switch completely disconnected from _anything_ at all.
If the flexible cable going to the immersion element is ordinary PVC insulated cable, this needs to be replaced with a suitable length of high temperature insulation cable (typically a high temperature rated silicone plastic compound) to comply with the regulations.
Incidently, it would have been better if you'd zoomed out to a wider angle when taking those photos so as to show which wires belonged to which cable. Luckily, close examination of the in focus pictures, along with your description makes it possible to work out what would have been instantly obvious from a wider shot.
[1] I'm assuming the copper pipework is cross bonded to earth elsewhere in the plumbing circuit.
I was just wondering is it was the combination of switches that was causing the problem. And after 11 tears of non use that could be possible:-)
Double check the wiring and post back (as others have suggested) especially the earth with the red sleeving.
The fact that there is only one immersion heater makes it easy.
Looks like a serious bodge and gr/yel been used as Neutral .... you should put this to right.
None of teh terminals on teh switch (3 on left and 4 on right) should be connected to earth.
In the past there has been a few attempted solutions to fixing the immersion heater to generate small and large amounts of hot water as needed. Some had two elements (long and short). Some had two thermostats.
At least three conductors are needed to achieve this. (plus earth) It looks like someone is using the earth wire in standard three core cable as the third conductor. (Bit naughty) instead of four core cable.
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