Worcester Greenstar 24i - No central heating

[David Margetts]

Hello - I've checked through the existing posts and there are a few that seem to refer to the same issues as I have but their solutions tend to be around the thermostat. I think my problems are not within the thermostat...

My Worcester Greenstar 24i junior combi boiler doesn't heat the central heating water. It heats the tap water just fine but when the demand comes in from the room thermostat for the central heating to turn on - nothing happens... I've checked the demand from the thermostat is reaching the circuit board (240VAC upon request) and is does (240 VAC on pin Lr). I can see the diverter valve moving up and down during initial switch-on, so that seems OK, I've changed the mains circuit board so that doesn't seem to be the problem either. The blue indicator light is on steady and doesn't flash to show any errors. What I've noticed is that if I put the unit into 'maintenance mode' the central heating works and the radiators get hot, so it seems that the basic functionality of the system is OK... I suspect I have a faulty sensor somewhere but looking at the circuit diagram, I can't see an obvious culprit.***

Any thoughts anyone?

 

[ianmcd]

What CH Timer do you have, you have an external control problem not a boiler problem

 

[David Margetts]

Hi Ian - thanks for getting back to me - The timer is a cheap digital external type, but I've confirmed that the demand signal is getting to the boiler by monitoring the voltage on pin Lr of the circuit board interface and it goes to 240 VAC when the timer/thermostat calls for heat. Bur just to be sure, I will short out the external theromostat/timer on the PCB and see what happens....

 

[ianmcd]

remove the external controls ane put a link between LR&LS

 

[jackthom]

Hi, did you check for 240V using a multimeter, connected between LR and Neutral?

 

[David Margetts]

To gound I think... but should be the same?

 

[David Margetts]

Off home to try it now.... talk later

 

[David Margetts]

Hi Ian. I tried shorting out LR & LS with the timer disconnected - nothing changed... Do you have any idea what you might expect to see across the various sensors that are scatter around? The user manual shows just a picture of them without giving any details on the expected resistance of logic state.

 

[ianmcd]

you shouldnt have changed the PCB , it is a gas safe only job , but too late now, did you use the origional code plug or one that came with the PCB ?

 

[ianmcd]

post a pic of the control panel on the boiler please

 

[David Margetts]

Hi Ian - I know I'm playing in other's 'sand pit' but I just can't help myself. (The systems I work on don't break down very often and I'm a compulsive 'fixer'
I used the original code plug to preserve the gas settings. Please find control panel attached. Once I work out what's wrong with it, I promise to get a gas safe chap in to check it out. (I think it needs new heat exchanger gaskets anyway - Second picture shows some 'Dr Who-like' matter oozing out).

 

[martyndc88]

That clock on the front is your problem. That's the heat exchanger leaking, not the gasket
My advice is don't use it until you get it checked by an engineer

 

[David Margetts]

Your advice is much appreciated - I will stop messing with it but from a technical point of view, the way I have it set up, that clock is not used in any way. The clock pins are all set to do nothing and the switch is set to permanently 'ON' so that the external timer/thermostat does all the switching. Do you think the clock is in some way dragging a rail down in the circuit - or something?

 

[martyndc88]

Set those pins in and it'll come on. The switch has failed

 

[ianmcd]

as i suspected you have an on board timer , it is connected to the 24v side and that is your problem , but not as serious as your heat exchanger gasket turn it off and get someone out right away