CH not coming on all the time

[con1_uk]

Hi, our house has a quite old classic LX system boiler with a separate HW tank, the CH is set to come on in the morning for just an hour of so and does but during the day if it’s cold or I haven’t lit the wood burner I turn the thermostat up but it don’t always come on, I boosted the HW the other day and the boiler instantly fired up. I have recently been tweaking the HW settings so it only comes on twice a day as opposed to being on all the time, could this be the issue? Does the CH rely on the water in the tank being hot?

Thanks.

 

[flameport]

Does the CH rely on the water in the tank being hot?

It certainly shouldn't. However if wired incorrectly anything is possible.

If it worked properly before, then a failed microswitch in a zone valve is likely, or the programmer / room thermostat has an intermittent problem.