MC2: 10/03/12 Page 40 of 90
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288
Modulex MLX Series Gas Fired Boiler System
Operation and Maintenance Manual
GAS SUPPLY OXYGEN (O
2
)
CARBON
DIOXIDE (CO
2
)
CARBON
MONOXIDE (CO)
NATURAL GAS 4.7% to 5.3% 9.1% to 8.8% <100 ppm
PROPANE 4.4% to 5.0% 10.7% to 10.4% <100 ppm
Combustion Calibration Procedure (Continued)
19. Verify that the oxygen (O
2
) level is within the range shown in Table 7-1 above. Also, ensure that the
carbon dioxide (CO
2
) and carbon monoxide (CO) are within the ranges shown.
20. If the oxygen level is not within the required tolerance, the gas valve for the boiler stage must be
adjusted. Remove the cap screw with a T40 Torx tool to access the Offset Adjustment Screw (Figure
7-3). Slowly rotate the Offset Adjustment Screw (in approximately 1/4 turn increments) in the desired
direction. Clockwise rotation reduces the oxygen level, while counterclockwise rotation increases the
oxygen level. Allow time for the combustion analyser to stabilize following each gas valve adjustment.
21. Once the oxygen level is within the required range for the first boiler stage, measure the gas pressure
at the outlet pressure tap. The pressure should be approximately 0.50” W.C. at the 10% fire rate.
22. Press the Program Key.
23. Using the Rotary Knob, set the displayed fire rate to zero (0). Press the Program key and wait until
the boiler stage turns off.
24. This completes the combustion calibration procedure for the first boiler stage.
25. Disconnect the manometer connected in step 3 and close the Outlet Pressure Tap by turning the
screw fully clockwise to its stop in preparation for the next boiler stage test.
On the controller, turn the Rotary Knob clockwise to the next Boiler stage. Repeat steps 16 through 25
for each remaining boiler stage (up to seven stages, depending on boiler size).
7.6 Unit Reassembly
Once the combustion calibration procedures have been completed for each boiler stage, the unit can
be reassembled for service operation per the instructions below.
Unit Reassembly
1. If it is still attached, remove the manometer from the gas valve outlet pressure tap. Close the tap by
rotating the screw fully clockwise to its stop.
2. Set the ON/OFF switch on the front of the Modulex boiler to the OFF position.
3. Turn off the gas supply to the boiler by closing the external shut-off valve.
4. Disconnect AC power.
5. Cover the hole drilled in the PVC flue pipe with foil tape.
Replace the top and side panels on the Modulex Boiler.
Table 7-1: Acceptable Combustion Gas Ratios at Boiler Input
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