Short burns on 333-F (WS3C)

[ducttape]

Hi guys,

I have a ~10y old 333-F WS3C. Recently I've noticed it's sometimes doing short 30 second burns. The issue is apparent on the attached image (green is the burner power in % and purple is the kessel temperature).

I don't know if it's related, but there are also some messages in previous months with fault code A8  - Internal pump reports air.

Any help would be appreciated!

[ducttape]

Another day, even more short burns (~1min). Around 40 starts in four hours. Any ideas? 

[qwert089]

Hi,

either you have air in the system and the water flow is not enough because of the air --> vent the air from the system and radiators

OR the heating pump has a mailfunction and must be replaced

[ducttape]

Hi, thanks so much for you help! I vented all the radiators a couple weeks ago at the start of the heating season, there was no air in them.

I am thinking, could that be related to the fact that most of the radiators being closed. Since it's not so cold right now my parents don't have all radiators turned on (only 3-4 out of about 12) and there being less water in the system to ciculate? Or is that irrelevant?

Besides the radiators, is there another circuit that needs to be vented?

[qwert089]

Hi,

the boiler itself has also a venting valve.

But this normally only need after installation.

https://www.viessmann.com/etapp/parts/de/0500/7246899

probably the small number used radiators is the problem.

BR