22
Manifold Pressure
Connect a manometer to the pressure tap at the outlet side
of the unit gas valve. Read the manifold pressure with the
main burners firing. The manifold pressure reading
indicated should be a (negative) -50 Pa (-0.2 inch water
column).
Adjust the evaporator fan rpm (at the motor sheave) to a
speed which most closely approximates the rpm value
found in the motor sheave/fan speed (rpm) table in the
Service Facts. To insure proper unit operation, the resulting
airflow must be or - 20 percent of the nominal
airflow rate.
After adjusting the evaporator fan, check heat exchanger
temperature rise during furnace operation to insure that it
falls within the range specified on the unit nameplate.
If the temperature rise noted is outside of the specified
limits, adjust the fan motor rpm to cause the temperature
rise of the heat exchanger to fall within the required range.
Open and lock unit
disconnect switch before continuing installation. Failure to
do so could result in severe personal injury or death due to
electrical shock or contact with moving parts.
Do not operate the unit
without the evaporator fan access panel in place. Reinstall
the access panel after performing any maintenance
procedures on the fan. Operating the unit without the
access panel properly installed may result in severe
personal injury or death.
Heating Shut-down
To exit the test mode, disconnect unit power for 3-5
seconds and re-apply. When running the unit using the
zone sensor as the control, position the selector switch at
“Off”. There will be a delay of 0 - 90 seconds before unit
shuts down in this setting.
Set the zone sensor to the desired set-point.
