A.O. Smith 100 Series Service Handbook page 59

RESTORE GAS FLOW SETTINGS TO DEFAULT
Each XB boiler/XWH water heater is fired and the optimal combustion set before leaving the factory. The High and Low Fire gas flow
adjustment screws on the 24 VAC Gas Valve have been set to maximize the boiler/water heater performance. When performing the
on site Start-up, gas flow can be improperly adjusted to the point the boiler/water heater will not light. This may require the valve to
be reset to a minimum gas flow (default) setting that will allow the unit to safely fire and perform the necessary adjustments outlined
in the Start-up procedure to ensure proper combustion and performance. Follow these steps to reset the gas flow settings to the
minimum gas flow (default) settings:
• With the boiler/water heater turned off. Use the correct size TORX® and/or Allen wrench to adjust the high fire and low fire
adjustment screws on the 24 VAC Gas Valve. Turn the High Fire adjustment screw clockwise and the Low Fire adjustment
screw counter-clockwise until they will not turn any more. This will close both gas flow adjustment screws. Do not overtighten or
use excessive force, turn the adjustment screws until they stop with minimal force applied.
• With both adjustment screws closed, turn the High Fire adjustment screw counter-clockwise 2 1/2 turns and the Low Fire
adjustment screw clockwise 2 1/2 turns. The gas flow settings are now reset to the minimum gas flow (default) setting.
• The boiler/water heater should light off with these minimum gas flow (default) settings. Make final gas flow adjustments and
ensure proper combustion and performance. If the boiler/water heater will not light off with the gas flow adjustment screws reset
as described above call the toll free support phone number on the back cover of this manual for further assistance.
BURNER INSPECTION
The stainless steel radial fire Burner used in XB boilers/XWH water heaters can trap debris drawn into the combustion air intake. This
can cause poor combustion, rough starting/operation and ignition failure. When cutting the intake air pipe sections during installation,
carefully remove all plastic debris left on the ends of each pipe section before installation to avoid this problem.
• Turn off the power supply. Disconnect the Venturi from the Combustion Blower. See Figure 7 on Page 15.
• Unplug the 3 pin and 5 pin plugs to the Combustion Blower Assembly. See Figure 4 on Page 11.
• Remove the Combustion Blower to get access to the Burner.
• Remove the Burner and inspect the burner for any signs of damage or debris inside. If the burner is damaged or contaminated
with debris - replace the burner. Check all gaskets in the burner/blower assembly for wear or damage. Replace any worn or
damaged gaskets.
Service Note
If the boiler/water heater is still experiencing poor combustion, rough starting/operating or ignition failure after all the steps in this
section have been performed call the toll free support phone number on the back cover of this manual for further assistance.
THINGS TO CHECK BEFORE SERVICING:
• Using the Instruction Manual that came with the boiler/water heater as reference, verify the water piping, gas line, venting and
electrical have all been properly installed.
• Ensure the power supply connections to the boiler/water heater are polarity correct and are properly grounded.
• Ensure supply gas pressure is within the minimum and maximum requirements.
• Review the Installation Considerations on page 3 and the Installation Check List on Page 8.
NOTE: Poor installations account for many service problems. Costs to correct installation errors are not covered under the limited
warranty.
RESETTING THE CONTROL SYSTEM
To reset the Control System from a lock out/fault condition; turn the power supply off for approximately 20 seconds and then back on.
Keep in mind if the condition that caused the lock out has not been corrected the Control System will continue to lock out.
IMPORTANT SERVICE REMINDER
When performing any troubleshooting step outlined in this manual always consider the wiring and connectors between components.
Perform a close visual inspection of all wiring and connectors to and from a given component before replacement. Ensure wires
were stripped before being crimped in a wire connector, ensure wires are crimped tightly in their connectors, ensure connection
pins in sockets and plugs are not damaged or worn, ensure plugs and sockets are mating properly and providing good contact.
Failure to perform this critical step or failing to perform this step thoroughly often results in needless down time, unnecessary parts
replacement, and customer dissatisfaction.
Servicing should only be performed by a Qualified Service Agent 59