COB-20 coughs/bangs/puffs after maintenance

Hello everyone,

In 2011, I had a new COB-20 installed in my single-family house. Since then, I have been doing the maintenance of the heating system myself. For this, I buy the maintenance kit and follow the instructions strictly.

Now it was time again. The heating system no longer ignited reliably; sometimes the three start attempts were not enough and the shower stayed cold. Yesterday, Saturday, I set about the maintenance again and, as usual, completed everything exactly according to the instructions. Afterwards, I thoroughly checked all the steps; I could not find any error.

Result: worse than before. Somehow I seem to have made a mistake or a new problem arose during the maintenance.

Since today and tomorrow are holidays and professionals are difficult to get at this time of year anyway, I now have a problem. Currently, the heating system is of course off.

What could be the cause? What repair attempts could I still carry out as a mechanically inclined layperson?

Many thanks for your help!

I don't know if my experiences with another oil condensing boiler (about 15 years old Weishaupt pre-mix burner) will help you. My problems and the corresponding solutions.

Unfortunately, the problem that caused 50% of my issues was oil shortage. (After shutdown, the two-pipe system ran empty or oil tanks were empty (they had no level indicator)) After conversion to a one-pipe system, it was better.

Oil pump defective. It ran but did not deliver (repair or replacement of the pump) Oil pressure measured?

Photodiode dirty. The diode (I believe) checked atomization; if nothing was detected, it did not ignite, cleaning easy.

Condensate in the exhaust pipe did not drain (had come loose a bit and thus changed the slope)

SOLVED!

Thanks for your tips. The new nozzle from the original maintenance kit was broken. I cleaned the old nozzle in the ultrasonic bath and reinstalled it, it worked immediately.

Happy New Year to everyone!