Hi all Having problems with CH. When the CH clock gets to off position at midnight, pump runs all through the night and boiler actually fires up and keeps rads hot. Even with the room stat turned down to 0. At the moment I'm having to turn the power off before I go to bed and then back on again when I get up. Obviously its getting warmer now so don't need rads on but I need hot water. Any pointers on what to look at first, could the room stat be knackered and keeps calling? CH clock kaput? or just pump? cheers.
Seems likely that you have an S-Plan system - with 2 or more 2-port valves.
The way these work is that the programmer and room/cylinder stats control the motors which open the valves. Each valve has auxilliary contacts in its actuator which close when the valve is fully open. These contacts are used to switch on the boiler and pump.
If one of these valves jams in the open position, your boiler and pump will run regardless of what the programmer and stats are doing. This would seem to fit your symptoms.
If yours *is* an S-Plan system, start by looking at the valves. You'll probably find that one of them is open even when the system is powered off. [If the rads are getting hot, it will be the CH valve which is jammed open rather then the HW one.]
Cheers by your description sounds like the sytem I have. Looking at the valve just below pump there is a manual lever that you can move to a manual position(open?) and its supossed to automatically go back for auto, but it seems non responsive and does not feel as if its doing anything,looks like a new valve is in order. Thanks for your insight it led me to look in the right place. cheers
If the lever moves freely with no resistance, it means that the valve is open - which it shouldn't be in the powered-off condition, but might be if jammed. [When working normally, you should feel some resistance when moving the lever, and should hear the whirring of gears in the actuator. Try the other valve, which is probably ok, and you'll see what I mean].
If - as seems likely - the valve isn't shutting when power is removed, this can be due to either of two reasons. The more likely one is that the 'wet' part of the valve has partially seized and has become too stiff for the return spring in the actuator to move it. The less likely one is that the return spring has failed. You can find out which one it is easily enough by removing the actuator from the valve. Chances are that you'll hear the actuator whirring to the closed position as soon as you remove it, and that the spindle of the valve itself will be stiff to turn. Assuming that is the case, you *may* be able to free up the valve by turning the spindle back and forth a few times with a pair of pliers. If that doesn't work, it's new valve time - which will require the system to be partially drained.
It would if it seized up after getting hot. This is quite a common failing, more so with Y plan but it happens with S plan too. Also some makes are prone to welding contacts in microswitches.If the OP is lucky he will have a valve with swappable powerhead but I'd go for trying the motor first..
Valve is open all the time and can be moved by spanner but actuator not working. I have taken off actuator and made CH go off/on but no response from actuator. Actuator looks old so will get whole actuator to save fault finding individual inners. Cheers
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