Modulating Gas (Fixed Air)
Procedure A: Low fire start
(Modulating Air or Gas)
Figure 4.6. Ratio Regulator
1. Drive air or gas control motor to low fire.
2. Be sure combustion air blower is running.
3. Open main gas manual shut off valves.
4. Set system control to stay at low fire during and after
(Low fire by-pass)
High-Off (Fixed Air)
Figure 4.5. System Layout
High-Low (Fixed Air)
Modulating Air (Ratio Control)
5. Attempt to ignite burner.
6. If burner does not ignite:
a.Attempt to ignite burner again to purge air from the
b.(Modulating Air) If burner still does not ignite, turn
bias adjusting screw
to increase gas flow.
(Modulating Gas) If burner still does not ignite,
adjust the control motor to incrementally increase
c.Attempt to ignite burner.
d.Repeat steps b and c until burner ignites. If
necessary, refer to Chapter 5 for troubleshooting
8. Flame signal strength: Adjust gas flow as described
above in step 7b to maintain a stable flame signal and
NOTE: If viewing the flame, it should be blue with flashes
of yellow. When firing propane or butane, a proper low fire
flame may have sustained flashes of yellow.
9. Verify low fire flame:
a.Shut off gas. Allow process to cool.
b.Verify repeatability of ignition and low fire flame
signal at cold conditions.
a half turn counterclockwise