Honeywell ST699

Product Information

Hi, I drained the the central heating, to remove a radiator. After refilling it, the heating now won’t work. Yes N & L were previously in N & L on the ST699. Regarding the locations of the other cables, I'm pretty certain that I did the following swap, although, I'm second guessing myself now: This is the existing wiring of the st699 I want to upgrade to a hive. I follow everything except the second blue wire that is going into the neutral port. The darker blue wire looks like an actual neutral wire , could the light blue wire be a switching wire that should have gone somewhere else? Hot water and heating calls currently work fine , occasionally the boiler fails to turn off but this is intermittent.

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.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.......................? 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...

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. Do you have a multi meter and able to trace the wires, in theory one core provides the live input to the boiler (#8) and one the live input to the pump (#3). I can see from your photo that there are two separate cables as the wires going ino terminals 1,2,3,4 on the ST9400 as they have slightly different characteristics

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As you say, the junction box on the floor is just to extend the cable from CH valve, so it doesn't hang in the air.

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. As you have power & lights on the ST9400C i guess that "Blue-A" and "Brown-B" were previously in ST699 N & L respectively. But can you say of the other four which terminals on the ST699 did they originate. My question is, as we have had to move some appliances around the kitchen, the st699 is now awkwardly behind the fridge freezer.Unit 16 High Carr Network Centre, Millennium Way, High Carr Business Park, Newcastle Under Lyme, Staffordshire, ST5 7XE Thanks Les. I have a multi meter and I'm reasonably competent at electrical stuff but I have little understanding of what signals what and when when it comes to central heating systems. 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

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.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).