Honeywell ST699

Product Information

Ahh..............interesting. It was in the middle. I pushed it to the "manual" end a few times and allowed it to return to the middle. Then when I switched the main switch on, the pump ran for a second or two then stopped, which sounds to be what should happen.......................? Yes, the picture of the ST699 is now - those are the linking cables left in after removing the other cables.

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. You can have hot water only, but you can't have heating only - the hot water has to be on for the heating to work, although I have no idea how the two are connected from a system point of view... I don’t know your boiler but would expect it to be redundant yes. I believe its there to be able to convert to a combi if needed. Sounds like there would be a bit more work involved in sorting the flexibility side out, as well as updating thermostatic room control, so I think I might just leave that bit alone until the day comes that I install a whole new combi-system.Graham, the motorised valve wiring - and what happens inside - is a lot more complicated than I thought! There's apparently a resistor/diode thingy going on which holds the valve in the CH positon even when the CH is turned off. The resistor is then meant to introduce enough of a resistance to turn the pump and boiler off. Yeah, I don't understand that either. 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!). 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. So hot water off on the programmer and hot water off on the tank thermostat but connect to the grey wire on motorised valve to turn DHW off, default is DHW on.

Does that mean hot water tank in airing cupboard which is heated via the boiler? (You may also have a separate immersion switch for the tank). I would really like to get rid of the thermostat in the hall altogether for cosmetic purposes and I would love to have more flexible control over the heating than the draconian timer we have now that has one setting for all days for both the heating and the hot water at the same time. Is it a DIY job or something a professional should do, baring in mind I don't want to replace the whole system, just the timer/thermostat of the existing system?

However, the ST699 has two simple switches inside, one for heating and one for hot water, and so does the Hive. From an electrical point of view they are the same, so you are simply exchanging one switch for another identical one. For exchange purposes, what's on the other end of the wiring is irrelevant really, provided that the ST699 was installed and working correctly in the first place. As you have a 3-port motorised valve connected [the clue is that there is a wire connected to the HW off terminal] then inside the motorised valve is a microswitch that controls the boiler when the heating is required, which means the Hive won't be controlling the boiler directly. Hive controls the motorised valve, and when the valve is in the central heating position that fires the boiler. The bypass provided a path from flow to return if both valves are closed buit the pump is still running. The manual valve should be replaced by an automatic bypass valve.

The Honeywell ST699B-1022 Electronic programmer is part of the Honeywell controls range at PlumbArena.

The one on the floor is more straight forward - it's just a like for like pass-through to extend the cable... Hi, I drained the the central heating, to remove a radiator. After refilling it, the heating now won’t work. The only reason I wasn't going to bother with downstairs was because we don't really have trouble with the heat levels downstairs, if anything it's hard to keep it warm even when heaters are on constantly as it is a large open plan space and has a very large bay window at one end and French doors at the other. I want to replace my st699 with the 9400. The install/conversion guide looks simple enough, but what do I do with the cables that are marked not connected (ie 5 and . Just think what if your away for a while in the winter and it was like last year and the power goes off. For 5mins work and 5 quid could save you loads of hassle.