Boiler stays on, when no demand (all valves working) ??

[ahdguy]

Bit of a strange one, but the bolier stays on, and only switches itself off when the water reaches temp.

I even went as far to take the valve motors off and check they work, (which they do). Every combination works the valves (including room thermostat),

Very confused, can't work out why the boiler thinks there is a demand all the time? Any ideas?

Thanks in advance.

 

[Agile]

Faulty switch in a motor valve?

Fault in your boiler whose make and model you are keeping very secret so that we cannot advise you in any detail.

Tony

 

[ChrisR]

+, what valves and how many?

 

[ahdguy]

Thanks for the responses guys, I've looked through the previous responses and nothing quite matched what I was seeing. - the boiler is unmarked.... A barratts cheapy one I expect (its not condensing). I'll take the cover off later and find out. Theres two seperate zone vales valves (2 port). One of the valves was replaced a couple of months ago (for a decent honeywell one, to replace the retro 60's one (seriously)), but it worked ok from then.

Out of interest, I always thought the timer dictated the boiler/valve operation? So if a microswitch went on a valve it just would stay in a particular position and you wouldn't get hot water or CH?
Or is it the case the micro switch on the valve, ie when valve switched open, switches on demand to the boiler?

 

[ahdguy]

Took the cover off and its a MAXOL microturbo 40 MDF. Cheers

 

[namsag]

Basically .The timer/room /cylinder stats only open the valves to allow water to flow through them.. The microswitch in valve has a permenant live to it which when the valve opens a cam hits the microswitch power then goes through it to the pump and boiler.. So if microswitch is stuck boiler and pump still get power without the valve being open

 

[ahdguy]

Ah makes sense now. Is there anyway to test for a stuck micro switch or bypass? I would gather its the remainging CH zone valve as the other one has been replaced recently.

 

[gas4you]

Check each orange wire off the valves for 230V. The stuck one will be the live one.