The power to start boiler then comes from cylinder stat if HW is involved or the valves orange wire if HW not involved.

A few weeks ago, I had some issues with my heating. The fault was found to be a damaged cable in the Kitchen wall, which was repaired / replaced. At the same time I found the 3-way valve in the airing cupboard to be leaking when set for heating. For the last few weeks I have had the 3way valve actuator wiring disconnected and have just been using the system for hot water. Today I finally got round to replacing the 3-way valve body and put a new (but not tested) actuator head on as the old one had visible signs of water damage. We provide a home delivery service through a number of leading courier agencies. Delivery charges are determined by how fragile, size and weight of the product(s) being delivered as follows: Wire (2) comes from the CH ON terminal, (goes via junction box) to the input side of the room stat, From the output side of room stat (goes via junction box ) to the white wire of valve. Note the CH and HW will now share the flow of water until one side becomes satisfied (usually HW) when the valve is then supposed to move to CH only.

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To do this the power lost from the white wire is replaced with power on the grey wire (micro switch breaks white and makes grey) It may be that HW is not on so the grey would not become live and this is where the second source comes in. Wire (1) comes from the HW ON terminal, (goes via junction box) to cylinder stat, then across the stat, then from cylinder stat (via junction box ) to boiler/pump. A wire from this terminal leads to the grey, which drives the motor forward to CH. While doing this a second micro switch allows power out of the valves orange wire to re start the boiler.