I have oil central heating with an internal thermostat as well as a pipe thermostat located in my garage. Although my heating is switched off at the Programmer, and all related lights are out, my pump continues to operate, sending heat to my central radiator only. This is happening 24 hours a day and I cannot stop it. I thought it may be due to my pipe thermostat activating to protect the pipes but this would appear not to be the case. When I switch the heating/water back on at the Programmer, it all acts normally. The only difference I have noticed is when I switch off at the Programmer - normally the pump closes down with a "clunking" sound but this is no longer happening. It does try to close down but something seems to be kicking in in the background. I'm confused. Any ideas anyone ?

I would use a meter and find out what control is causing this.Could be the protective pipe t stat is locked on.

Many thanks for taking the time to reply to this. The problem worsened and began a reverse process whereby when the Programmer was switched off the heating actually came on and vice versa. I have now had my Heating Engineer out and the problem was that one of the CH port valves was broken and was stuck in the "on" position. This has now been replaced and all's well, thank goodness as there is very heavy snow forecast for my area over the next 24 hours!

Actually there is nothing wrong with the pump running all winter long, there are some advantages to this and often systems wher hooked up this way. Just a side note I thought I would mention.

I agree but now days the pump cycles with the call for heat. Weather used as the heat control or upon activation by a zone valve. I loved the old days. One pump one stat and one boiler. That was when you really had to know how to calculate your load by zone. Then some smart guy decided to use brass gas cocks to fine tune the zones. Nothing like a fixed restrictor to get it right. To bad those days are gone for the most part.

Nothing like leaving all that heat in the boiler core and saying a vent damper makes it more efficient.

Now you guys are WAY over my head! Suffice to say I am delighted that the valve has been replaced, albeit with a horrid-looking Honeywell one as opposed to the nice-looking Myson one I had ! Now I have a nice-looking Myson valve for my water and a horrid-looking Honeywell valve for my CH (two-way twin-port system) but at least it works. Thanks again for your responses.

Lol