Central heating behaving oddly

[dcan]

My gas boiler supplies both heating and hot water independently. Recently the pump only switches off if the hot water side is switched off (either on the timer or by manual over-ride) before the heating side. Switch off the heating before the hotwater and the pump keeps running (and the pump noise increases) and the gas burner may also reignite (if the thermostats demand). Both valve actuators appear to operate normally. I have replaced the timer/control unit with a new one but the unusual behaviour persists. Any ideas anyone?

 

[seco services]

sounds like a sticky microswitch in the actuator.

 

[D_Hailsham]

Which boiler do you have - make and model?

Is it a fully pumped system - i.e the pump circulates water through the radiators and the hot water cylinder?

Do both the valves have two ports?

Is one valve in the heating circuit and the other in the HW cylinder circuit?

Do you have a thermostat on the HW cylinder?

A photo of the valves and HW cylinder would be helpful.

 

[gas4you]

Sounds like the CH actuator head is faulty and you don't have a by-pass valve fitted to the system.

 

[dcan]

Which boiler do you have - make and model? IDEAL CLASSIC FF370

Is it a fully pumped system - i.e the pump circulates water through the radiators and the hot water cylinder? YES

Do both the valves have two ports? YES

Is one valve in the heating circuit and the other in the HW cylinder circuit? YES

Do you have a thermostat on the HW cylinder? YES

A photo of the valves and HW cylinder would be helpful.NO CAN DO FOR THE MOMENT

 

[dcan]

Thanks everyone for your helpful advice - I think the problem is fixed now - a sticky microswitch - if not, I'll be back.......

 

[dcan]

My optimism proved misplaced even though I replaced the hot water valve actuator! It seems that fiddling about with any component results in the system working fine but only temporarily. I wonder if this may be due to everything getting a bit cooler while I work on it and have it switched off? The other evening a lot of hot water was drawn off shortly before the timer was due to shut the system down for the night. The hot water and the central heating then shut down normally at slightly different times as programmed and restarted normally the next morning. However last evening when no significant amount of hot water was used the programmer tried to shut everything down but the pump just kept on running and eventually (after an hour or so) I cut the power, but not before I very briefly manually over-rode both the HW and the CH (when the programmer said everything was switched off) and of course the gas started and ignited but when I shut everything down again manually the gas just kept on burning! So with the gas burning and the pump running the only means left to shut things down was to cut the power.... Does this now sound like a boiler fault? I have replaced the programmer and the HW valve actuator. The CH valve seems to open and close ok and the cylinder thermostat seems to work ok also. What else is left?

 

[gavinda]

did you chnage the right actuator...?

 

[gas_man_gaz]

like gavinda says prob the other actuator but id check the shafts aren't seized or stiff.
what boiler have ya got? and wen ya turn the heating and water off and the pump continues to run, does the boiler turn off or does it carry on burning?

 

[dcan]

Its IDEAL CLASSIC FF370
Turning off HW and CH kills the burn but if I then over-ride manually and the gas reignites, the gas continues to burn after I switch off again

 

[gavinda]

you need to examine the heads operation individually, both on and off of the bodies. check the spindles arent sticking and if so, replace them. a few of the motorised valves out there will have service kits and be easy to repair on a bung set.

 

[dcan]

Again, thanks for the help. It really is fixed this time - replacement actuator on the CH side