Boiler constantly on

[davidgrayston]

Hi All. Hoping for some guidence here.
Our boiler now runs constantly. Also, with just the HW on we seem to get some heat 'leaking' into a few of the rads.
Ive had a problem since early spring and Ive been 'bodging' by turning off fused spur to system when we didnt want hot water. Now we need heating Misses has given orders that Ive got to sort!
Boiler is Potterton Suprima 100L with Drayton Tempus 7 timer.
My DIY assumption, as an IT person, is that the zone valve to the CH is probably stuck partially open, right or wrong? The bit Im really not sure about is that there are 2 seperate one port valves for a single CH zone. I.E single pipe Tee's and there is then a single port valve on each side it then Tee's back to a single pipe.
Im guessing this isnt to increase overall flow, so assume they do different jobs. One maybe for frost overide?
The CH valves are labelled as Drayton ZA6. The HW zone valve is different, a Honeywell V4043H1056.
Im I barking up the right tree? If so any tips on how I prove where the problem is?
Cheers for any help!
Dave.

 

[ChrisOxford]

Way out of my depth here, Dave, but can you see/hear the valves open/close? They can also be operated manually, which might help you diagnose what's going on.

 

[davidgrayston]

I tried to google some instructions on using them manually as I didnt want to force any thing and make it worse.
I could only find Drayton ZA6 on two port valves so no wiser.
I will take the motors off an go through the timer options to see what triggers what.
When the motors are off Im guessing its best to leave the valves all open so that the boiler can run up at if its triggered?
Cheers.
D.

 

[seco services]

you've more likey got a sticky micro switch or the valve is jammed open.
Is the boiler firing up with the programmer both set to off ?

They are 2 port zone valves no single port.

 

[Space cat]

The usual way to wire the boiler in such a system is to connect all the valves' switches in parallel then use this combination to power the boiler. In such a system, if any one valve is stuck open, its switch will keep the boiler running all the time. Since you have heat reaching the radiators when only HW is on, maybe one of those two CH valves is stuck.

Feel the pipes to see whether boiler water is going where it shouldn't. To find out where the boiler is getting power from when it should be off, trace any wires that could do this. I would expect them to connect to switches within zone valves. Disconnect each one in turn (power OFF of course) and isolate it in choc block then see if the fault has gone.

 

[davidgrayston]

Thanks for the info.
Yep, got description of valves wrong. Just to confirm they aren't the two way, just open/close.
Im I right in thinking the two valves that are setup in parrallel for the single zone do different jobs? If one is for the frost protection is there a way of triggering a test of it?
Cheers.
D.

 

[davidgrayston]

Well that was easier than expected!
When I took the 2 actuators off I noticed one had a rattle. When I took the cover off a spring and remains of its plastic hook fell out.
Just fitted replace unit and all working fine now.
Cheers.
D.