Honeywell ST699

Product Information

Does the timer allow you to have HW only in the summer but, in the winter you must have both CH and HW on at the same time?

Yes as a default I will just replace the wires to the exact layout of the Honeywell , utilizing the L N 3 and 4 terminals on the Hive.If you need any assistance with that, post back details of the existing room thermostat and a photo of its wiring connections. 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. Then, just before Xmas, it started to switch off (the display disappeared) and either the heating or hot water just went off.

My question is how difficult would it be to replace just the timer and thermostat (with a wireless one) without touching anything else in the system?

If it's an older system with pumped heating and gravity circulation of hot water, then the Hive should be set to gravity mode. Is it as simple as looking at a wiring diagram for the ST699 and attaching to the corresponding connection of a new timer? Whilst the fundamentals are similar from installation to installation, some items are different, and where the actual connections are made will vary based on the layout of the components in your home and the personal preferences of the original installer. As I mentioned earlier and you have seen for yourself wire colours often mean diddly squat in heating systems. To view the purposes they believe they have legitimate interest for, or to object to this data processing use the vendor list link below.

so if theres a power cut the controller will retain the clock info and timings and switch heating on as soon as power is back on. Having said that I suppose it can't hurt to put a TRV on the kitchen radiator as that doesn't really need to be on while we're in there cooking, worth considering I suppose. Hi all I have read the wiring diagram and suggestions regarding converting from Honeywell st699 to St9400c timer but all guidance describes changing from the basic wiring to the new terminals in the st9400c.Ive had this heating programmer for 20 years and it works fine unless I have a power cut, which happens out in the sticks occasionally. Yes, the picture of the ST699 is now - those are the linking cables left in after removing the other cables. It just seems odd there are 2 wires into the Neutral on the Honeywell and I wonder if the boiler not turning off sometimes is caused by a NC terminal not being connected.