Central heating radiators coming on when not required

[wilsond]

Hi, having trouble with my heating controls and could use some help.

Since we moved in about a year ago this has been happening so thought I need to do something about it now the winter is coming.

The problem is the radiators come on when the time clock central heating switch is off if the hot water tank thermostat is off.

This causes the heating to come on during the night unless i turn the room thermostat down which means a cold house though in the mornings.

I have had the time clock changed and that hasnt helped.

I think the system uses the Honeywell Y plan and an ideal standard floor standing boiler if thats any help.

Any ideas would be appreciated - thanks

 

[MANDATE]

If you have a Y plan, you will have a 3 port mid position valve in the pipework just after the pump. The options are HW or CH or with valve in mid position both HW and CH take an equal share until one of them becomes satisfied, at which point the valve moves to the one still to be satisfied.
I can only think this problem is due to the valve being in the CH position or mid position and supplying power to the boiler, when it shouldn't.
The time clock provides the power to the room stat which in turn provides the power to the valve which provides the power to the boiler /pump.
If the time clock is ok, then the next thing to check is the room stat. does it make and break contact as you turn it up and down? (test with meter )
If thats ok you need to veryify if the valve is operating correctly.
You need to listen and observe what happens when you have different situations.
The valve goes through about 90 degrees, it's fixed to a gear quadrant so the motor turns about 6 or 7 turns. The quadrant is spring loaded so when power is removed it goes back to the start positon which happens to be HW.
there is a lever on the side that can be used to turn the quadrant against the spring and move it to the final position.
It could be the valve spindle is sticking, and the qaudrant not returning correctly. It could be incorrect wiring of the valve, even the spring.
Get someone to switch all the power off to the system and you should hear the valve return to start position, then operate the lever against the spring.
With HW off CH off room stat down, put power back on (nothing should change). Next put CH on (still nothing should change) except you should have power at the room stat. Now turn up room stat and this should move valve from start positon to final position. If you turn the room stat down again the valve does NOT return to the start positon. Now with room stat down or CH off turn the HW on and the valve will after a slight delay go to the start positon with the force applied by the spring.
You can try it with both HW ad CH and the valve should either move 'up' to or drop 'back' to mid position.
You have to understand how these work, carry out some tests and apply some logic to get some indication of where the problem lies.
If it's a wiring fault I suggest you look at other posts on this aspect.
I think I've run out of other ideas.

 

[wilsond]

I give it a try, that's very helpful

 

[wilsond]

I have tested the valve and it seems to go through all the positions at the different settings of the thermostat, timer etc, etc.

I have checked every wire from each component back the wiring board and they all seem ok. The only wiring I can't check is the wiring in the three port valve as i think the cuboard has been built around it !!!

The heating comes on when both timer switches (HW & CH) are off and the tank stat is off not when its on, does this suggest power being fed back from the HW off feed from the timer back to the boiler and pump via the valve wiring ?

The only way to check the valve wiring is to remove it in which case, looking at the age of it, I might as well replace it. Sound like a good idea ?

Is this a difficult job ? Will the new value fit the old pipe and olives without having to re-plumb anything, as its a bit tight in the cuboard and I dont fancy my chances of having to fit new pipework.

Thanks very much