HRM Wallstar won't start

[Charliecharlesworth79]

Hi hope someone can help,

The boiler has been working fine all summer heating the hot water, but now the cold weather has come we've started having problems:-
The motorised valve for the heating sounded like it was repeatedly trying to actuate but failing to, this has been replaced with an identicle model, the central heating pump was also replaced as it has been getting noisier over the last couple of years (12 years old).
Now when the central heating (or hot water) is switched on the pump works and the motorised valves open, but the boiler doesn't start.
The boiler fires and heats for a few minutes if I press the reset button, but then switches off again.

Having to wait a while for an engineer/plumber (busy time of year) hoping it might be something simple.

Thanks in advance

 

[Burnerman]

Are you talking about the burner locking out here, or the boiler overheat trip needing resetting?
John

 

[Charliecharlesworth79]

Thanks for your reply.
The lockout (red) light is not illuminated. When hot water or heating is switched on (by programme or extra hour function) the boiler doesn't start but the mains light is on. If I press the reset (outside) button the boiler fires up for a few minutes then stops, but still no red light. (I'm assuming the lockout bulb hasn't blown!).

Hope this helps

 

[Burnerman]

I'd assume that the boiler can't get rid of the heat it is producing, which could mean an airlock, no power to the new pump or indeed the pump valves being left closed......what do you reckon?
John

 

[Charliecharlesworth79]

I'll check your suggestions, thanks.

 

[Charliecharlesworth79]

Checked valves which are all open, have bled pump and rads, pump runs so must have power also both HW and CH valves open when system is switched on.
But still the boiler won't start up, I've also checked thermostats are turned up!

 

[Burnerman]

The boiler does start, but then shuts down and can be reset with the overheat stat - is that still correct?
I still suspect air in the system and if I remember there is an automatic air vent on the top of the heat exchanger.....if you can find it, try unscrewing it's cap to see if there's any air present.
John

 

[Danoil]

When you say you press the reset button outside and it fires up for a few minutes, does it actually fire or is it just the fan that spins?
The reset button on the control box outside only resets the burner from lock out.

Like Burnerman says, these normally have a bleed vent on the top corner inside depending on age so it may be worth you checking for that, as it does sound like air trapped around the heat exchanger causing the boiler limit stat to cut in. Which you would have to reset inside.

 

[Charliecharlesworth79]

Thanks for the replies, just to clarify, the boiler does not fire up when the CH/HW is switched on, but will if the reset button it pressed, then it runs for about 10 minutes before shutting off again. When it runs it is heating the radiators and I can feel hot exhaust gasses from the flu.

What signals the boiler to start working? Studying the wiring diagram the two orange wires from the motorised valves should give it the feed (they are connected).

 

[Andy4444]

So are you pressing the burner reset button or overheat thermostat reset ?

 

[oilhead]

oil pump solenoid.

 

[Burnerman]

If its the burner lock out lamp that's on, that has to be a safe bet!
John