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Posted 20 hours ago

Honeywell ST699

£9.9£99Clearance
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I do know that there is a Grundfos pump in the airing cupboard next to the cylinder and two white boxes connected to the pipes which I believe are motorised valves, but that is the extent of my knowledge - the airing cupboard is a bit of a spaghetti junction or pipes and wheel valves, and I don't really know what any of them do! I just opened them all when I first moved in and hoped for the best, I've never touched them since lol. Ok, try this; power off, and move the lever from one extreme to t'other a few times. What does it feel like? Does it move smoothly against spring pressure? Both ways? Does it make a faint 'whirring' sound both ways? Where does it 'settle' when released? Hi all I have a Y plan system with a mid position valve and original honeywell st699 controller. I replaced the wiring as shown. It seems that the hot water does not fire up the boiler on its own. It will work when heating is selected. I did not switch the system to gravity fed. If I change to this will it start working correctly. Hopefully someone can answer this for me. 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).

of the current 3 wires in the wall with the (neutral maybe?) with its box off but as shown in the photo previously all were just wired into seperate boxes. Any idea which to connect to get the circuit closed again?

Early batteries were removable and Varta make a replacement for about a fiver. You could try Maplin among other suppliers. 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. 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.

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 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 I thought the job was done however it seems that the heating still won’t come on… can’t tell if the hot water is working as when I turn the shower on it is hot but we do have a hot water tank. Any help would be appreciated I can’t see where my wiring is wrong but as you may have gathered this isn’t my strong suit.

When it didn't work, I've Googled again and come across this Forum. Whilst I can find a few issues other users have had, I can't find anything that relates to my issue. I have noticed however, that the old wiring to the ST699 that is redundant, wasn't as per the diagram I saw in one of the posts. I have cables linking: Prior to the ST699 failing did everything work as you would expect. What you programmed as the hot water on/off cycles is what happened. Likewise for the central heating. 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. 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!

My question is, as we have had to move some appliances around the kitchen, the st699 is now awkwardly behind the fridge freezer. They've both got what looks like a switch with A - B settings, the one on the pipe running down past the cylinder is set to B, and the one on the pipe running into the cylinder is set to A, someone has also written on this one with a marker pen putting a C next to the A and an O next to the B (presumably meaning open and closed?).

With the older type of systems, (without motorised valves) it's not possible to have the heating 'on' without the hot water being 'on' as well. These are usually older systems installed before 1980's, but can be upgraded. Changing the Hive to gravity mode just makes it automatically turn the hot water on whenever the heating is selected on. I assume the current picture of the ST699 is after it has been removed from the wall and it's sitting on a table so to speak. The Honeywell ST699B-1022 Electronic programmer is part of the Honeywell controls range at PlumbArena. 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. 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.

Yes, the picture of the ST699 is now - those are the linking cables left in after removing the other cables. Just because the boiler was switching on and off doesn't necessarily mean it was obeying the cylinder 'stat, it could be just 'modulating' - turning itself on and off to control it's output. (As the cylinder heats up, so will the hot water return. So the boiler needs to provide much less heat to this water before it sends it around again. Ergo the boiler may need to shut itself off for a short while. In this case, the pump would keep running.) Is it as simple as looking at a wiring diagram for the ST699 and attaching to the corresponding connection of a new timer? I opened up the Honeywell wiring hub near the boiler power switch to try to get a better idea of what the wires were doingHowever, 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.

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