Ok, so last night I tried to replicate the problem. I had no joy, the system worked flawlessly through all combinations.
I woke up this morning and the same issue occurred. The HW was off. The room stat was calling for heat. The RX1 light was on. The programmer was on for CH only. No boiler firing.
I opened the junction box to the valve. It's just a straight one to one connection. Everything goes through the wiring centre.
View media item 51169
The grey and white wires were live but the orange wasn't. Unfortunately I couldn't find my multimeter (I know this was requested and is probably the key to working out the problem) so I just used an electric screwdriver to check the current.
I opened the wiring centre and checked which wires were live. According to the diagram I linked to earlier in the thread all the currents seemed fine to me except for the link to the orange wire at the valve (which made sense). The room stat connections (2&3) were live. The timer connection (9) was live. The grey and white wires from the valve were live (4&7).
Turning the hot water on fired the boiler as the cylinder stat was calling for heat. The rads heated up (as they should because at this stage the HW and CH were on and both stats were calling). The orange wire was now live, white and grey remained live. I turned off the HW and the orange wire went dead, white and grey remained live.
I turned off the CH and turned on the HW - White was dead, Grey and Orange were live, boiler was firing.
I turned off the HW and turned on the CH - Grey, White and Orange were live and the CH operation returned to normal.
Something somewhere in the valve isn't right but I'm not sure what.
The wiring centre is below but not sure what you will make of it:
View media item 51170
I woke up this morning and the same issue occurred. The HW was off. The room stat was calling for heat. The RX1 light was on. The programmer was on for CH only. No boiler firing.
I opened the junction box to the valve. It's just a straight one to one connection. Everything goes through the wiring centre.
View media item 51169
The grey and white wires were live but the orange wasn't. Unfortunately I couldn't find my multimeter (I know this was requested and is probably the key to working out the problem) so I just used an electric screwdriver to check the current.
I opened the wiring centre and checked which wires were live. According to the diagram I linked to earlier in the thread all the currents seemed fine to me except for the link to the orange wire at the valve (which made sense). The room stat connections (2&3) were live. The timer connection (9) was live. The grey and white wires from the valve were live (4&7).
Turning the hot water on fired the boiler as the cylinder stat was calling for heat. The rads heated up (as they should because at this stage the HW and CH were on and both stats were calling). The orange wire was now live, white and grey remained live. I turned off the HW and the orange wire went dead, white and grey remained live.
I turned off the CH and turned on the HW - White was dead, Grey and Orange were live, boiler was firing.
I turned off the HW and turned on the CH - Grey, White and Orange were live and the CH operation returned to normal.
Something somewhere in the valve isn't right but I'm not sure what.
The wiring centre is below but not sure what you will make of it:
View media item 51170