Honeywell ST699

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Find a Plumber Plumbers Looking for Work - Post Here Looking for a Plumber? Post Jobs Here Looking for a Heating Engineer? Post Jobs Here Find a Renewable Energy Specialist Plumbers Directory Listings I've attached pics of the ST9400C wiring before and after the swap (ST9400c Wiring 1) and a pic of the remaining wires in the ST699. Not seen a Y Plan using gravity, in the main the DHW is the default mode, and the tank thermostat turns on the boiler for DHW and the tank thermostat when satisfied powers the grey wire which will cause the motorised valve to open all the way so only have central heating, the white wire powers the valve half way if no grey but all the way if grey also live.

The wires at the Honeywell ST699 move to the Hive terminals that have exactly the same function. Where there are two wires in a terminal both wires make the transfer and stay connected together. It's often the case that a standard cable L, N, E is used to connect a room thermostat and the N conductor is often used as the switched live. It should really have a brown sleeve over it (or red in the case of older installations) to indicate that it is being used as a live, but not all do, as you have discovered. 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? I have the same problem with mine and I just moved in to new house has this device. I tried everything but it still works for both of them at the same time. 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.

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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?). 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! Hi, I recently replaced a 27 year old Honeywell ST699 Programmer with a new ST9400c. Whilst system delivers Heating and Hot Water, it will not deliver Hot Water when HW only is selected (despite green LED being illuminated) i.e. boiler does not fire. My wiring changes were as follows: to the terminals of the dual channel Hive that have exactly the same functions. So N goes N, L to L, Hot water on, to Hot water on etc... But this has got me thinking, why stop there? Our boiler is controlled by an ancient looking Honeywell timer which from Googling I think is a Honeywell ST699 (except our version features a delightful brown/beige colour scheme!) There is also an equally old looking thermostat dial in the hall (just above the radiator which doesn't strike me as an ideal location!).

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. 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. The old room thermostat can't simply be disconnected as this would leave the heating wiring 'open circuit' and the heating will not operate, so, the two live wires that used to go to the thermostat then need to be joined together to complete the circuit. This can be done where the thermostat was by putting them in a junction box, or at their origin, and then the old thermostat cable can be disconnected completely. The one on the floor is more straight forward - it's just a like for like pass-through to extend the cable...

I also had problems configuring Nest, it used terms like system boiler and mine is not a system boiler the pump is exterior, and it switched on the domestic hot water at what seemed random times, it turned out is was anti legionaries and it could be disabled, but took me ages to find out why it was doing it. Early batteries were removable and Varta make a replacement for about a fiver. You could try Maplin among other suppliers. 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!). 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. But I see a post like yours, and I think of my central heating, I have two pumps, two motorised valves, the domestic hot water and bathroom radiator is thermo syphon, no control other than boiler run time as to domestic hot water, and closest plan is a C Plan, I still am not sure of pipe layout, but I have got a wiring diagram of the system.

You have what they call BASIC SYSTEM 1 or 2. Gravity hot water, pumped CH and with/without room thermostat. Now just need to see how that maps to the ST9400. However you should ensure you know what went where on the ST699. The use of three blue cores, two brown cores and one red core coming into the ST699 is a recipe for confusion. Strangely enough the links between terminals is the least of the problems. I'd recommend you tidy the wires a bit. The number of loose strands is a disaster waiting to happen. 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 .Hi, I drained the the central heating, to remove a radiator. After refilling it, the heating now won’t work. 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. 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.

I opened up the Honeywell wiring hub near the boiler power switch to try to get a better idea of what the wires were doing 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. 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. 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.

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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: