7.4.3
Setting the air/gas ratio (reduced heat input)
1. Unscrew the left-hand plug, which corresponds to the flue gas
measurement point connection.
2. Connect the flue gas analyser to the connection on the left.
Important
Ensure that the opening around the sensor is completely sealed
when taking measurements.
Insert the sensor into the flue gas measurement point to at least
8 cm for SIRIUS THREE FS 50 and SIRIUS THREE FS 70 .
Insert the sensor into the flue gas measurement point to at least
9 cm for SIRIUS THREE FS 90 and SIRIUS THREE FS 110 .
3. Set the boiler's heat input to 0%.
4. Measure the percentage of CO
2
in the flue gases.
5. Compare the values measured with the authorised CO
2
range in the
Control and setting values table.
Important
The CO
2
settings range at reduced heat input depends on the
CO
2
value measured at maximum heat input.
6. If necessary, adjust the air/gas ratio using the OFFSET adjustment
screw.
Important
Turn the gas adjustment screw clockwise to increase the CO
2
content.
Turn the gas adjustment screw counter-clockwise to reduce the
CO
2
content.
Caution
Be sure to correctly replace the plug after taking a measurement.
For more information, see
Check-list before commissioning, page 56
CO2 checking and setting values, page 61
Using the boiler according to thermal output, page 88
7.4.4
Gas valves
Tab.28 Settings values for a new gas valve on SIRIUS THREE FS
Boiler model
Nominal heat input:
Number of turns for the gas flow rate set
tings screw
Minimum heat input:
Number of turns for the OFFSET set
tings screw
SIRIUS THREE FS 50
12
5 + 3/4
SIRIUS THREE FS 70
13
5 + 3/4
SIRIUS THREE FS 90
2 + 2/3
5 + 3/4
SIRIUS THREE FS 110
2 + 1/3
5 + 3/4
Fig.66
Connecting the flue gas analyser
MW-3000046-03
2
1
7 Commissioning
60
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