Honeywell ST699

Product Information

We have good water pressure in the house so I don't think a combi would be a problem, however that's a couple of years off yet (or until the current one dies!).

Yep like that - they're called 'Lifestyle 2-port motorised valve', there is one underneath the pump on a pipe that doesn't go into the cylinder, and one on a pipe that come off the other pipe and goes into the cylinder about halfway up it. Unfortunately wiring colours tend to be meaningless with heating systems. One installer may use a blue wire for a certain purpose another may use a brown for the same function. So never assume a blue wire is actually being used as a neutral it may be being used as a live. It's what a wire is connected to at each end that determines its function, not the colour of its insulation. You had a hard wired link between Live, 5 (common for CH) and 6 (Hot water on). That's why I thought your hot water was permanently on. There was also a hard link between 3 (CH on) and 7 (HW off). Then there were connections to all four terminals for CH on/off and HW on/off which is not normal. So I wonder if the other end of those wires go to the expected places. That said based on your prior ST699 wiring. I think your hot water was permantly on as you had linked L->5->6 . And the HW-OFF (7) was linked to CH-ON (3).No, I meant "have" cables linking on the ST699 as they are still connected. So I disconnected the power supply, the boiler and the water and these were left connected. I can confirm the hot water was never permanently on and came on twice a day. We also have the option of switching on the emersion for water.

As an aside my 'bay' window is more like a box on the side of the house, it's not full height and as far as I can see the large window sill is the only thing separating it from the outside, which seems like a horrible design from an energy saving/warmth point of view considering all the other walls have cavity wall insulation.

Each Google Nest product works out how to make your home better. So imagine what they can do when they work together. If Nest Protect detects carbon monoxide, the Nest Thermostat can turn off your boiler, because it's a common source of CO leaks. And when the Nest Protect senses smoke, it can turn on Nest Cam to help find out where it came from. I've been doing a lot of research on heating systems recently, and for those that have seen my other topic I've been having trouble with a cold radiator which I think will need new valves.