Minimum Output Calibration; Final Check And Ignition Failure Adjustment Procedure - Watts AERCO MLX EXT 321 Installation, Operation & Maintenance Manual

Modulating and condensing boilers
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CHAPTER 4: Installation Instructions

Minimum Output Calibration

After setting the maximum gas output for each valve (section 4.35.2), refer to Figure 4-38,
above, to locate the Minimum Gas Adjustment screw (B) on each valve. Follow the instructions
below to set the minimum gas output level for each valve.
Adjusting the Minimum (B) Gas Output Setting
1. Operate the burner to a minimum power following the procedure described in section 4.36
(Figure 4-40) ''Sweeper'' function (CASCADE MAN 10%).
2. Check that the CO
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If necessary, correct the value by turning the adjustment screw "B" in a CLOCKWISE
3.
direction to increase the value or ANTICLOCKWISE to decrease it the value.
4. Repeat the adjustment for all gas valves in the boiler.
NOTE:
If the CO
percentage is too low, check if the air and exhaust flue are obstructed. If they are not
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obstructed, check if the burner and/or the exchanger (aluminum sections) are properly cleaned.
After confirmation, check the maximum gas settings again, as described in section 4.35.2,
above.

Final Check and Ignition Failure Adjustment Procedure

After completing the Minimum and Maximum output adjustments, check the CO
maximum values at the flue outlet and, if necessary, make any required adjustments.
If the boiler fails to ignite, perform the following procedure:
Figure 4-39: Maximum Output Adjustment Screw
1. Tighten the maximum adjustment screw "A" in a clockwise direction until it is fully abutted
into the gas valve body, than slacken back out for nine (9) turns.
2. Verify boiler ignition.
3. If the boiler goes into lockout, slacken the screw "A" again for one turn, than retry ignition.
4. If the boiler goes into lockout again, repeat step 3 and retry ignition.
5. Once ignition succeeds, carry out the minimum and maximum gas output burner
adjustments as previously described in sections 4.35.2 and 4.35.3, above.
OMM-0087_J • GF-143 • 11/17/2020
values are within the values indicated in Table 4-6.
Ignition Failure Adjustment Procedure
Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST
minimum and
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