Manual

14
20. Open the main gas shutoff valve. Disconnect the wire from the "A4" terminal block. This
will cause the unit to call for continuous high fire.
21. Check the outside air temperature and add the nameplate temperature rise to this value.
Measure the discharge air temperature. Adjust the main gas pressure at the main
pressure regulator until the proper discharge temperature determined above is reached.
On units with the Maxitrol MR212 valve, there is no separate regulator. Adjust the main
gas pressure at this valve (refer to the Maxitrol installation instructions).
22. Observe the main burner flame for proper flame length. The flame should be 13-16" in
length, as measured from the end of the burner to the end of the stable part of the flame
(exclude any wisps of flashes). If the flame is too long, if it contains excess yellow flame,
or if it tends to rise, low air velocity is indicated. If the flame is very short and all blue,
excess velocity is apparent. Shut down the heater and adjust the profile plates as
required.
23. If profile plates have been adjusted, then recheck the temperature rise as in step # 23.
Adjust the regulator if necessary.
24. Reconnect the wire to the "A4" terminal block. Disconnect the wire to the "A8" terminal
block. This will cause the unit to call for continuous low fire.
25. Reduce the low fire stop on the modulating valve until the flame tends to go out. Then
increase it to the smallest stable, full length fire. If a local weak spot appears, check for
clogged low fire air ports. Make low fire adjustments patiently. Due to the low gas flow
rate, response to adjustments will be slow. Refer to the Maxitrol installation instructions on
how to make these adjustments.
26. Reconnect the wire to the "A8" terminal block. Remove the jumper on the high
temperature limit. Reset the remote temperature selector to the desired discharge air
temperature.
27. Check unit for proper function of the control operations (refer to the Controls Description
and Testing section).