NOTE: Btu content of the gas should be obtained from the
gas supplier. This measured input must not be greater than
shown on the unit rating plate.
6. Relight all other appliances turned off in Step 1. Be sure all
pilot burners are operating.
Main Burner Flame Check
Flames should be stable, soft and blue (dust may cause orange
tips but they must not be yellow) and extending directly outward
from the burner without curling, floating or lifting off.
Temperature Rise Check
Check the temperature rise through the unit by placing
thermometers in supply and return air registers as close to the
unit as possible. Thermometers must not be able to sample
temperature directly from the unit heat exchangers, or false
readings could be obtained.
1. All registers must be open; all duct dampers must be in their
final (fully or partially open) position and the unit operated for
15 minutes before taking readings.
2. The temperature rise must be within the range specified on
the rating plate.
NOTE: Air temperature rise is the temperature difference
between supply and return air.
With a properly designed system, the proper amount of
temperature rise will normally be obtained when the unit is
operated at rated input with the recommended blower speed.
If the correct amount of temperature rise is not obtained, it may
be necessary to change the blower speed. A higher blower speed
will lower the temperature rise. A slower blower speed will
increase the temperature rise.
NOTE: Blower speed must be set to give the correct air
temperature rise through the unit as marked on the rating plate.
External Static Pressure Check
The total external static pressure must be checked on this unit to
determine if the airflow is proper.
Blower Speed Adjustments
To avoid personal injury or death due to electrical shock,
turn OFF power to the furnace before changing speed taps.
Refer to the wiring diagram in the Appendix to verify speed tap
For models equipped with PSC type motors, blower speeds are
to be changed at the ignition control board. Both heat speed and
cool speed terminals are supplied on the board along with
2 unused motor lead terminals.
Some models are equipped with X-13 motors. X-13 motors are
constant torque motors with very low power consumption. This
motor is energized by 24V. Adjust the CFM for the unit by
changing the 24V low voltage leads to the speed terminal block
on the motor.
NOTE: Heating airflow must be adjusted to provide the
temperature rise shown on rating plate.
Check limit control operation after 15 minutes of operation by
blocking the return air grille(s).
1. After several minutes the main burners must go Off. Blower
will continue to run.
2. Remove air restrictions and main burners will relight after a
cool down period of a few minutes.
3. Adjust the thermostat setting below room temperature.
Main burners must go Off.
Circulating Air Blower will continue to run for 120, 135 or
150 seconds, depending on the setting.
NOTE: If necessary, adjust the Fan Off Delay settings to obtain
satisfactory comfort level.
This unit must not be used as a "construction heater"
during the finishing phases of construction on a new
structure. This type of use may result in premature failure
of the unit due to extremely low return air temperatures
and exposure to corrosive or very dirty atmospheres.