new member..ferroli domi compact problem

[peetee effee]

hi just been working on ferroli domi compact 30 combi boiler
getting weird results with my analyser
high ppm and ratio poor [ burner chamber cleaned etc. ]
burner pressure okay.
flue run is horizontal and length is 4 metres
this is just over the maximum length for this
termination.
Flue joins are well secure etc. restrictor removed
i am sure combustion air is getting into air intake
or recirculating...but cannot see any faults.

any ideas

 

[SimonJohns]

You just had the answer. Flue is too long