Boiler comes on with timer off

[martinjjones]

I have a problem with the boiler in the house. Even with the timer set to off, it comes on and indicates a call for heat. The pipes that get warm appear to be the one to the hot water tank. The problem used to be intermittent but now appears more permanent and I've tried some diagnostics from researching some posts on here

The system has two 2 port valves. The orange wires from each valve are joined together at the junction box and are joined to a brown wire that goes under the floor. With the mains on the brown is always at 240V. With neither of the orange wires connected then there is no call for heat. With the valve for the CH connected and the hot water isolated then there is a call for heat (timer off and thermostat turned down) and the boiler lights but again seems to heat the hot water. There are no volts at the hot water valve orange wire.

With the orange wire to the hot water valve connected to the brown wire and the orange wire from the CH isolated then there is 240V to the HW, nothing on the CH, and no call for heat with the boiler.

interestingly, having done the test in that order with it all connected back up it now seems to be working (for the moment that is) with no call for heat and the timer turned off.

Since it was the hot water that keeps getting warm with everything off, i had assumed that the HW valve was either stuck or faulty. The spindle moves fine with the head off and the lever moves and springs back to auto as well. But by virtue of the fact that the call for heat occurs with the HW valve orange wire isolated I'm beginning to doubt it and think its the CH valve. So why is it only ever the HW that warms up.

I don't have a frost stat unless its built into the boiler ICOS Ideal HE15. Is the timer broken instead (Potterton). Or is the thermostat on the hot water tank playing up and just asking for continual heat?

Advice?

 

[twgas]

Sounds as though one of the end switches is not opening when the valve closes.
I'm not to sure of your diagnostics, or the way you explain it.
Try disconnecting the two valve orange wires, make them safe, preferably with choc-blocks. Now turn HW on (prog on cyl 'stat up). Check for power at orange wire. Turn off then check again for power.
Turn off HW and do the same tests on CH. if you get 240v on 1 of the oranges when the valve is off the head needs replacing.

 

[martinjjones]

Untitled

• martinjjones
• 5 Feb 2013
• 2

Attached is the image of my junction box. Both the orange wires from the valves go into the same connection and have one brown wire in the same block. (5th from the top) The brown wire goes into the floor. I have tried to compare the box with a standard S plan diagram but can't seem to get it to match nor with the S plan with a pump overun.

The brown wire is always live whenever the mains is on irrespective of the boiler being on or any call for heat from either circuit. If I isolate either of the orange wires on its own i never get any volts on it when i compare with the top terminal (neutral?)

Does that help?

 

[twgas]

Sounds as though it was installed using the orange as the perm live, which means the greys from the valves will be switched lives. Disconnect the greys, make them safe and seperated then do the tests I suggested for the oranges.