Froling P4 Error: Combustion air supply faulty or blocked

[phollands]

Started the boiler today after the summer shutdown and getting a "Combustion air supply faulty or blocked" at end of the preparation phase.

Spent hours checking values and cleaning inside the boiler, air intakes and the flue. Have also recalibrated the Lambda probe which is only 12 months old after having failed during last summers shutdown (lessons learnt...don't turn these boilers off for an extended period)

Does anyone have any suggestions? I'd rather replace a failed part based on an incorrect status value rather than just swapping parts in hope. Previously the Lamdba probe error messages was a clear "Sensor element of the broadband probe faulty"

From what I understand the boiler only has 2 sensors, Lambda and flue temperate, so I'm assuming its using the Lambda to measure the oxygen.

Current values below which seem to be relevant. I haven't changed any values, but just not sure what value the preparation phase is monitoring for before throwing the error

• Residual Oxygen content - Usually around 21% during preparation
• Oxygen Control 35%
• Residual Oxygen content setpoint 9%
• O2 Controller max 120%

Many thanks!
Paul

 

[phollands]

After having another go at following wires and digging around in the back of the boiler, I believe I've found the air flow sensor.

The connection to the component at the end looks very sorry and whilst you could maybe reflow it...might as well replace the board. Will update how I get on

 

[chew72]

Good find.

 

[phollands]

Odd that I provide a resolution to my own question, but happy to help the community.

The original error is thrown since the mass air flow sensor is faulty. This is used to measure the movement in air flow and is the first test performed by the boiler during the Preparation phase. You can see the status of this sensor within the Current Values menu (when in Service mode) and its called "Air speed at suction opening". Mine was previously reporting 4.4m (meters/second) and it didn't change during the preparation phase. Once I'd replaced the sensor and started the boiler, the value now started to change during preparation (reducing down) and got to around 3.9m when the boiler then moved to the pellet loading phase.

Speaking to my parts supplier, apparently the part is well known to failure and can also cause the "Self test error during preparation" error message. Generally for this reason they recommend you keep a spare mass-flow sensor and lambda probe.

The mass-flow sensor is in the back of the boiler behind the bottom panel and connects to the pellet circuit board via a black flat cable with an RJ11 jack plug on each end.

I'm intending to try and repair the original sensor. The circuit tracks on the probe end are in a very bad state.

Hope this helps someone else. Feel like I'm becoming an expert on these boilers.