Baxi Ecogen 24/1.0 Installation & Servicing Instructions Manual page 68

Fig. 74a
Fig. 75
Fig. 76
page 68
15.2 Air/Gas Valve Setup Procedure
The preferred method is to use a micro manometer as outlined below, however if a micro manometer is not available a combustion analyser may be used as described below.
Using a Micro Manometer to adjust the valve offset.
Procedure to correctly set new Air/Gas Valve using a micro manometer. Connect the micro manometer with the appliance off ­ fan not running as below.
1. Loosen screw in the internal pressure test point (PINT) and connect to + (positive) side of differential micro manometer.
2. Tee the ­ (negative) side of the micro manometer into the air sense tube (Fig.77).
3. Ensure micro manometer is in Pa or mbar scale and has zeroed correctly. If in doubt, re­zero the instrument.
4. Use the chimney sweep function to enable either Engine or Supplementary minimum rate. Before the air/gas valve opens, the pressure shown should be negative ie. ­30Pa
or ­25Pa respectively for each burner.
5. When the burner lights see that the reading is ­5 to ­6Pa if outside these values use the offset screw to adjust the 4mm hexhead underneath the dust cover.
NOTE: Turning adjustment screw clockwise reduces negative differential; anticlockwise increases negative differential.
A 4mm hexagon key should be used to make the adjustment.
6. Now check the combustion ­ Carbon dioxide and Carbon Monoxide at the maximum rate for each air/gas valve.
Using a Combustion Analyser to adjust the valve offset.
Follow the procedure as outlined in section 15.1. paragraph 1­6 to adjust the Carbon Dioxide percentage at the maximum rate.
For the supplementary the CO2 should be 9.0% ± 0.3
For the engine the CO2 should be 9.0% ± 0.3
Propane Gas ­ When either burner is tested individually at maximum rate: The CO2 should be 10.2% ± 0.3.
1a. To adjust the offset check the Carbon Dioxide percentage at the minimum rate. Remove the offset adjustment dust cover using a flat bladed screw driver and adjust the offset
using a 4 mm hex driver to give the following percentages: ­
Supplementary the CO2 should be 8.7% ± 0.3 (minimum rate)
Engine the CO2 should be 8.8% ± 0.3 (minimum rate)
Propane Gas ­ CO2 at minimum rate:­
The CO2 should be 9.6% ± 0.3 for the supplementary
The CO2 should be 9.8% ± 0.3 for the engine
2a. Recheck the Carbon Dioxide % at max rate, adjust the throttle adjustment screw if necessary.
3a. The differences between the maximum/minimum percentages should be as close as possible to the differences in the ranges quoted; they must not be equal or less.
i.e.: ­ For the Supplementary burner maximum rate, the Carbon Dioxide should be around 0.6 % greater than at the minimum rate.
For the Engine burner maximum rate, the Carbon Dioxide should be around 0.2% greater than at the minimum rate.