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- 2 May 2022
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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:
ST699 9400c
1 Live To L (Red)
2 N ——- N (Black)
3 ——— 4 (Red)
4 was empty
5 - 8 Link was discarded
L - 5 Link was discarded
6 ——- 3 (Yellow)
7 ——- 1 (Blue)
8 ——- 4 (Red)
I suspect that the Red wire from terminal 8 on ST699 to terminal 4 on ST9400c may be the problem, but not absolutely sure which terminal it should go to on 9400c. Can’t find on-line where to move Red wire at terminal 8 on St699. My system comprises 8 year old Bosch Worcester boiler, Drayton MA1 Mid level valve, new Honeywell DST90E room therm. Any advice would be appreciated.
ST699 9400c
1 Live To L (Red)
2 N ——- N (Black)
3 ——— 4 (Red)
4 was empty
5 - 8 Link was discarded
L - 5 Link was discarded
6 ——- 3 (Yellow)
7 ——- 1 (Blue)
8 ——- 4 (Red)
I suspect that the Red wire from terminal 8 on ST699 to terminal 4 on ST9400c may be the problem, but not absolutely sure which terminal it should go to on 9400c. Can’t find on-line where to move Red wire at terminal 8 on St699. My system comprises 8 year old Bosch Worcester boiler, Drayton MA1 Mid level valve, new Honeywell DST90E room therm. Any advice would be appreciated.