Pump/boiler not switching off despite no demand Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[u33446z]

My system is a pumped HW+CH using Ideal Minimiser SE condensing boiler and 2x 2 position valves (Drayton ZA6 actuators), controller by a Siemens RWB9 controller. 2 or 3 years after installation there were occasions when there was no demand on the system and yet the pump continued to run but worse, the boiler fired up and quickly made 'boiling' and clanking noises before it shut itself off. My installer suggested one of the actuators might not be commanding th epump and boiler off when it arrived at its closed position. He diagnosed which one and replaced it. All was fine for a few more years (till now) when the symptoms returned. So I replaced the older of the two actuators, but it hasn't solved the problem,

Any ideas anyone?

[stoneyboy]

u33446z,
Replace the newer actuator.
end

[rosebery]

I think I'd suggest you get your system checked by another person.

[u33446z]

Problem diagnosed as a sticking microswitch in the younger of the two actuators. Replaced microswitch and all is well.