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My three port motorized diverter valve needed to be changed and I couldn't get a plumber for the best part of a week due to Easter break, so I bought one and fitted it myself.

Fitted no problem and I wired like wire to like wire. However, when I removed the electrical junction box cover panel, a wire for the hot water tank temperature gauge came loose and I have no idea where it came from.

It's an earth wire (bottom middle of picture), but it has a red sheath around it so I sought some advice and was told it is an earth, so wire it to the other earth wires on the right! It made sense as from what I can see, there is no other earth to the hot water tank temperature gauge based on the wiring loom there.

I switched the electrics to the heating back on and the control panel lit up, I then switched on the heating and the control panel indicated it had done so, I then about five seconds later switched on the hot water and I heard a 'tick' or 'click' sound coming from either my hall thermostat, or from one of the electrical items by the hot water tank (temp gauge, pump or 3 port valve)... not the control panel I was in front of. As soon as I heard the sound, the control panel powered off.

Now the whole thing seems to be dead. I've changed the fuse by the control panel, but nothing is showing on it.

Any thoughts on what might be the issue? Where should this loose 'earth' wire go? Have I got to replace something else?

Thanks in advance.

It's a pity you didn't remove the cover of the junction box before deciding to change the valve. If one of the wires from the cylinder thermostat was disconnected the old valve will not have worked correctly.

The red sleeve on the "earth wire" indicates that it is being used to carry voltage and could be live. So connecting this wire to earth and turning on has shorted something out. We need to work out what, to see if it's caused major damage.

Please post:

1. Which junction box terminals the 2 wires from cylinder stat are connected to.

2. Which JB terminals the white, grey and orange wires from the valve are connected to.

https://www.honeywelluk.com/professiona ... -Diagrams/

The wire will go to one of the following:

Orange from 3 port valve
HW ON from programmer
HW OFF from programmer

Technically, one should never use the G/Y to carry voltage, but it is a regularly ignored rule. NEVER assume the colour coding is correct.