Honeywell ST699

Product Information

If only 3 & 8 were originally connected as per pdf .... For a gravity HW system, the hot water coming on fires up the boiler and the central heating being on powers the pump. To get you up and running should require the following links on the ST9400C

Ideally I would like a modern digital timer with flexibility for multiple programmes for different days and times and a wireless thermostat in the living room to control the temperature. And one that doesn't lose all it's settings whenever there is a power interruption! 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?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... Whilst wire colours do necessarily mean anything on a central heating system, the combinations you have are a bit unusual. For example blue being used for CH on & HW on and brown for hot water off. That's based on your indication above about wiring on ST699. Apologies for the focus in these pictures, I can assure you it isn't down to your drunken eyesight. I don't know what my digital camera was playing at today (I really ought to read the manual). Step 3. Lie the facia onto it's front and open out the PCB by unclipping the rear board from the retaining posts. See that white lump? Looks like a battery to me. 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.

If you have a S-Plan system with a single heating zone 3 for HW-On and 4 for CH-On, nothing to either 1 or 2. It's all connected and I've set the time and date, all is okay. However, even though the lights come on, it won't fire up either the heating or the water!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.