Worcester heatslave 25/32 Hot lockout

[Aeroengineer]

Hi all, just looing for a little guidance on our oil boiler. We have the following issue. Boiler fires up fine when cold and continues to run normally with its fire up process controlled by the thermo. As the boiler gets warm ... at least an hour of continuous running the ignition process takes longer and longer till we end up in a lockout situation? Does anyone have any ideas. Any help or guidance appreciated.

 

[Terrywookfit]

Check the solenoid coil resistance when the boiler locks out.

 

[xr4x4]

It's running continually for an hour?

Somethings wrong with it!

 

[Aeroengineer]

Check the solenoid coil resistance when the boiler locks out.

Resistance is fine, just a slight change from cold to hot as would be expected but defo not open circuit on shutdown.

 

[Aeroengineer]

It's running continually for an hour?

Somethings wrong with it!

 

[Burnerman]

When you say the start up takes longer, whats actually happening?
(The solenoid coil is definitely the main suspect - keep one in stock anyway) and the motor has a start capacitor that can fail from time to time.
John

 

[Aeroengineer]

When you say the start up takes longer, whats actually happening?
(The solenoid coil is definitely the main suspect - keep one in stock anyway) and the motor has a start capacitor that can fail from time to time.
John

Its goes through the normal start up process. I.e. Blower - Ignition - fuel solenoid - flame to abbreviate a little. the point between ignition and flame is stretched beyond the safety limits and therefore lockout although you can hear the solenoid click in, oh, and pump pressures good. But as I said at the beginning when cold runs as you would expect with no issues till warm approx. an hour of running

 

[Burnerman]

OK so we have to clutch at the odd straw here.....the burner should purge for about 6 sec or so, and the ignition spark is there too. After that, the control box clicks, switches power to the solenoid coil, which opens the valve inside the pump. Or does it? I wonder if that valve is actually opening!
I suppose the photocell could be affected by heat too, so it thinks that the flame is still there - its only an LDR after all.
John

 

[Agile]

Where is the heat going from this boiler when it runs for an hour?

Is the heat loss of the rads matched by the boiler output even though we are well above freezing at the moment?

Tony

 

[Aeroengineer]

OK so we have to clutch at the odd straw here.....the burner should purge for about 6 sec or so, and the ignition spark is there too. After that, the control box clicks, switches power to the solenoid coil, which opens the valve inside the pump. Or does it? I wonder if that valve is actually opening!
I suppose the photocell could be affected by heat too, so it thinks that the flame is still there - its only an LDR after all.
John

I thought that initially, but like I said the boiler works perfectly when cold. it sounds like a delayed ignition the warmer it gets you know that blowback sound you get if the spark gap mal adjusted of transformer starts to go dickey

 

[Aeroengineer]

Where is the heat going from this boiler when it runs for an hour?

Is the heat loss of the rads matched by the boiler output even though we are well above freezing at the moment?

Tony

Works as normal Tony, Heating or water whatever is selected on the controller. Heat generated is what you would expect no chang there

 

[Burnerman]

The position of the electrodes can certainly affect the start up procedure - often giving a thump as the burner ignites....if they are set too far back.
That symptom is there hot and cold though.
John

 

[Aeroengineer]

Agreed John, when cold solenoid click and you have instant flame but as warms up that period just get longer and longer over a period of about an hour! I think i'm leaning towards the pump to be honest! What would be your opinion on the check valve in the nozzle tube? what effect would that have? Have you seen a problem with a check valve in the past?

 

[Burnerman]

Well, it could be the pump valve, who knows?
They are available separately from www.heating-parts.co.uk if you want.
If you buy a new Danfoss pump though, they do come complete with a solenoid coil and naturally the valve itself.
John

 

[Aeroengineer]

John I have never come across an issue with the check valve in the nozzle tube what symptoms does that present you with if faulty? have you seen this before?