APPENDIX I: BURNER FIRING RATE CALIBRATION
High fire adjustments
NOTE: THE MODULATING/REGULATOR VALVE IS LOCATED ON THE GAS TRAIN.
SEE GAS TRAIN DRAWING FOR LOCATION OF VALVE.
In order to set the High Fire gas pressure correctly, three terms must be understood. They are:
1. Differential Gas Pressure: This is the difference between the burner negative and the high fire gas
pressure. The maximum differential gas pressure is shown on the rating tag
located on the weather enclosure door. A typical setting is 8.0” W.C. for
natural gas.
2. Burner Negative: Is measured with the fan ON, and the burner OFF. External ductwork and
filters can affect burner negative. This should be checked after the installation
is complete. Using a manometer measure the negative pressure at the gas
piping downstream of the modulating regulator valve; normally at the high gas
pressure switch.
3. High Fire Gas Pressure: Is measured with a manometer connected in the same place as above. The fan
must be ON and the burner forced to high fire. The desired high fire gas
pressure, being adjusted in Step 3 below, is the difference between the burner
negative and the differential gas pressure.
1.Force the burner into high fire. This will place approximately 20VDC at the
modulating gas valve coil.
2.Remove the seal cap (A) on the Regulator to adjust the high fire setting.
3.Turn the Regulator adjusting screw inside to achieve the pressure called for on
the rating tag.
Clockwise rotation increases pressure.
Example:
Differential gas pressure 8.0" w.c.
Burner negative pressure -1.0" w.c. (must be measured)
High fire gas pressure 7.0" w.c.
4. Replace the seal cap (A).
Low fire adjustments
1. Force the burner into low fire
2. Remove the seal cap (B) on the low fire setting.
3. Loosen the lock screw (C) inside and then adjust the screw (D) until achieving a continuous ribbon of flame
across the entire burner. Clockwise rotation reduces the minimum flow rate.
4. Tighten the set screw (C).
5. Replace the seal cap (B).
K:\SERVICE\Tech Forms\Appendix I_AH.doc - rev. date 04/15
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