ACTUATOR/ motorised valve problem ******

[MarkAqua]

Hey just a quick questions,

Got a call off a customer today and having trouble with her hot water and heating. What is happening is, when she turns her heating on the hot water just keeps getting hotter and hotter. They're is a motorised valve fitted and a cylinder stat both are 3 years old.

So the motorised valve isnt shutting off when the cylinder reaches temp,

Do you think its a dodgy actuator?

Regards,

 

[mfgs]

dodgy motor or sludge not allowing the valve to fully close.

 

[MattWeth]

I'd check the stat first.

 

[Mike Jackson]

Has this been a problem since they were installed. I've seen quite a few S plans incorrectly wired where the grey and brown wires have been commoned together to save a live feed to the valves. This can lead to power backfeeding through the switch and holding a valve open when the call for heat has ended.

 

[MarkAqua]

She says it has been okay and this started before xmas.

i've just been over there and took the actuator off. put the hot water on and the valve opens. when I turn down the cylinder stat past the click it isnt shutting down the motorised valve..

 

[MarkAqua]

oh and it is a Y plan. cheers

 

[diamondgas]

On hot water only the valve should be at rest markaqua. The spring return runs the valve back to hot water only position. It's only with a call for heating that the valve will move.

 

[MarkAqua]

Right I see, cheers for the reply. Any ideas to what the problem could be? The valve is moving and seems to be working so im leaning towards the cylinder stat. Will test it with a multi meter tomorrow.

 

[Roger Welton]

-h/w only call, v/v at returned to h/w position by spring, boiler and pump fed from cylinder stat
-h/w and heating call, v/v drives to mid position and stalls (feed on white) boiler and pump still fed from cyl stat
-heating only, v/v drives fully open (feed on white, heating call and grey h/w satisfied) pump and boiler fed from orange on 3 port (limit micro-switch)

If the v/v is driving all the way over correctly and still getting heat to port b then v/v must be passing. I like to see the system cold and fire for heating only, it soon becomes apparent what is happening.

 

[MattWeth]

As I said above my gut feeling is cylinder stat.

Edit: Nice post from Roger re the control logic.

 

[diamondgas]

Can't say any more than that Roger I too am a touchy feel kind of guy when it comes to circulation

 

[MarkAqua]

thank you very much for all of your replies they are greatly appriciated.