I've come back from being a way a couple of days and the house is freezing, although plenty of hot water!
The system is open, gas fired Myson Orion boiler with Honeywell timer.
Before I went away, I had turned just the heating on on the timer, the boiler would fire.
This evening, when turning the heating on, the boiler didn't fire but would if H/W was turned on. With just CH on, I checked the thermostat and that was clicking at about 10 degree. That had no effect.
So, next I checked the control valve in the airing cupboard (Honeywell). The control valve has three connections - one from the pump, one to the hot water cylinder and one to elsewhere.
At first when I moved it to manual (open) from auto, nothing but I realised that when it was moved fully over to manual, rather than resting in the lock position, I could hear a microswitch and then I heard the boiler fire.
I'm sure that I've had this before.. Anyway. What should trigger the valve to move? Obviously when open, the switch is working but the valve closes - I've not had the top off but I'm guessing it is spring loaded?
So, I'm wondering what isn't working correctly. Is it the thermostat or is it the valve? How can I test that? I'm assuming that I should be able to take the thermostat out of the loop, ie bridge it somehow if I can work out the wiring.
I suppose if the valve then works, that points to the thermostat, else it is the valve?
For now, to get heating, if I put the valve into manual I can get the radiators to start to work. What I'm not sure of is if doing that, my radiators will only work when my hotwater needs heating - but having the valve in manual (open), does that mean I have CH and no H/W and with the valve the other way, H/W and no CH? For that, I can sort of live with whilst I sort the rest out.
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