central heating with a mind of its own

[saynor]

My central heating system decides to switch itself on even at odd times even when the clock for water and heating if off. What could cause this?
Could it be a faulty motorised valve to the central heating. (it has another for the water.
The valve is a a drayton Z6.

 

[namsag]

Edit. earlier answer removed read the question wrong.

If its turning on when clock is off then it will be a faulty microswitch in one of the valves and your central heating valve is passing
Or the heating valve is completly shot and stuck open and making the micro switch

 

[rebuke]

I had a similar problem - my central heating would turn on randomly even when the programmer was claiming it was off.

After I did some troubleshooting, it turned out it was wired in a Honeywell box with labelled terminals for everything, and whoever had installed it hadn't read the note on the lid that says "If using with a programmer, cut link 1" - a quick snip and all was sorted...

 

[saynor]

thank you for your helpful replies. I will explore the switch first and then the valve. Hopefully it will be just the detatcheable switch.

 

[daveaf]

My central heating started doing a similar thing lately, I have a Digistat 3 programmable thermostat and despite it being set up for different temps, it just decided to make up its own mind about when it was going to come on and how hot it wanted to get.
After searching this forum, I found a post about somebody resetting the stat by holding down 2 buttons together and it cured the problem. They referred to it as a "Control Alt Delete"
The back up batteries (if Fitted) can also play up even if they are not showing the battery low light. So again a simple thing to eliminate before stripping valves etc..