Valves overriding by themselves

[AndrewWSmith]

I successfully installed an Evohome system in 2019 with an ATP921R3100 basepack, an ATF500DHW hot water pack and 9 individually scheduled HR924UK valves. The valves are scheduled to turn down to 10C overnight so that the boiler will not come on while we are asleep.

Generally speaking the system has worked well, but a couple of times in the last few months we have been woken up by the boiler firing up even though all rooms were well above 10C. On investigation I found that one or two of the valves are showing an override to their normal daytime setting. The overrides were certainly not set by us, and we have no pets or children who might have changed the valve settings accidentally.

Has anyone else had this problem, or can anyone suggest what is going on and how to fix it.

[Richard]

Did you override the system after the final time change? This is the most common reason evohome demands outside of the setpoint as it will run until the next time change (next morning).

[AndrewWSmith]

On the night the problem occurred, before I went to bed I had checked that all valves were set to 10C, without any overrides and the System Summary table showed all valves and the boiler control at 0%. I did not make any adjustments after that.

My reason for checking the status of the settings is that some valves occasionally fail to shut down completely despite them being above the set temperature, and the boiler will then continue firing. However, Incan fix that problem when it occurs by increasing the temp setting to open the valve and then resetting it to the scheduled low temperature, though a permanent solution would be nice.

I did not need to this on the nights when the boiler fired up after being off for several hours because of the overrides I did not set, so I assume it is a different problem.