Ofsh Reset needed after every thermostat shut off.

[Raco]

Hi, wondering if any of you have come across a gun type oil burner that needs reset every time the thermostat shuts it off? What can cause this? I have a spare known good burner, I have swapped over control box and photo resistor but still does it. Once started burner will run happily for hours. Once zone thermostat or boiler thermostat shuts it off it won't restart on it's own without reset. It's not a proper lockout as the red light is not illuminated but still requires the button to be pressed. Any ideas?

 

[SimonG]

Do you have a picture of the burner? When was it last serviced? What was the co2, flue gas temp, excess air etc?

 

[Raco]

It's a bentone st108, just to confuse things a bit for you it isn't running on kero. It's been converted to run on waste engine oil. So co2 and stack temps wouldn't be within spec anyway. All main functions still controlled with original control box except nozzle preheater. I did try this burner before converting it and it was doing the same thing on kero. It will run happily for hours on end as long as thermostats call for heat. Once power it cut, button needs pressed.

 

[Brambles]

Are you controlling this through a Honeywell 834 box? The symptoms that you describe is that the burner is loosing the permanent live. It always needs to be reset when cold starting.

Suggest that you recheck the wiring configuration - make sure that the polarity is correct too - albeit normally if that is incorrect, it won’t fire at all.

 

[Raco]

The live is switched through the boiler stat, same as the old boiler was and it worked fine this way, I'll investigate this a bit further when I get home thanks

 

[Brambles]

Was it the same burner in the old boiler?

 

[Raco]

Sorry i ment it was wired the same as the old burner. Never changed the boiler. both burners are st108's. Looking at the bentone installation pdf from Google, there is no permanent live, just live, neutral, and earth, with the thermostats switching the live. Which is the way it is currently wired.
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Problem found! It wasn't anything to do with the burner at all it was a solid state relay on the pid temperature controller. Brambles you were bang on, the boiler thermostat does not completly break the circuit, whereas my solid state relay after the stat did.

 

[Brambles]

Really pleased that you found the solution. The Honeywell controller referred to above, avoids the condition you encountered.