035-17443-000 Rev. A (800)
16
Unitary Products Group
5.
Once the correct gas pressure to the burners has been
established, turn the gas valve switch to OFF and turn
the electrical supply switch OFF; then, remove the pres-
sure tap at the gas valve and re-install the plug using a
compound (on the threads) resistant to the action of LP
gases.
6.
Turn the electrical and gas supplies back on, and, with
the burners in operation, check for gas leakage around
the plug with a soap and water solution.
ADJUSTMENT OF TEMPERATURE RISE
The temperature rise, or temperature difference between the
return air and the heated air from the furnace, must be within
the range shown on the furnace rating plate and within the
application limitations shown in Table 3. After the temperature
rise has been determined, the airflow (cfm) can be calcu-
lated. Refer to Blower Performance Matrix, Table 7 on page
22.
After about 20 minutes of operation, determine the furnace
temperature rise. Take readings of both the return air and the
heated air in the ducts, about six feet from the furnace where
they will not be affected by radiant heat.
Increase the blower speed to decrease the temperature rise;
decrease the blower speed to increase the rise. Blower
speed adjustment is made as follows:
1.
Remove the belt and loosen the set screw in the adjust-
able flange of the motor pulley.
2.
Close the pulley to decrease the temperature rise; open
the pulley to increase the rise.
3.
Position the set screw with one of the flats on the pulley
hub and tighten it.
4.
Align the fixed flange of the motor pulley with the blower
pulley.
5.
Adjust the belt tension with the motor adjusting bolt until
the belt can be depressed 1" with a finger at a point half-
way between the two pulleys. Loosen the (4) motor
mount bolts to permit adjustment. Retighten bolts after
adjusting.
6.
Repeat the pulley adjustment procedure until the
desired temperature rise is obtained.
ADJUSTMENT OF FAN-OFF CONTROL SETTINGS
This furnace is equipped with a time-on / time-off heating fan
control. The fan on delay is fixed at 30 seconds. the fan off
delay is field adjustable from 60 to 180 seconds. The fan off
delay is factory set to 120 seconds.
The “fan-off” setting must be long enough to adequately cool
the furnace, but not so long that cold air is blown into the
heated space. The “fan-off” timing may be adjusted by posi-
tioning the jumper (refer to Figure 11 ) located on the con-
trol board.
ACCESSORY CONNECTIONS
The furnace control will allow power switching control of vari-
ous accessories. Refer to Figure 12 for connection details.
Electronic Air Cleaner Connection: Two 1/4" spade termi-
nals (EAC and EAC N) for electronic air cleaner connections
are located on the control board. The terminals provide 115
VAC (1.0 amp maximum) during circulating blower operation.
Humidifier Connection: Two 1/4" spade terminals (HUM
and HUM N) for humidifier connections are located on the
control board. The terminals provide 115 VAC (1.0 amp maxi-
mum) during heating system operation
Twinning: When two furnaces are installed using the same
duct system, it is very important that the two furnaces circu-
lating air blowers operate simultaneously. If one blower starts
before the second blower, the duct system will become pres-
surized with air and the second blower will be made to turn
backwards. During heating operation, this will cause over-
heating of the second furnace, possibly causing an unsafe
condition and damage to the furnace. If twinning of two fur-
Be sure that the gas valve pressure regulator cap
is replaced.
Improper alignment will cause excessive noise,
belt wear and bearing failure.
FIGURE 11 : FAN-OFF TIME ADJUSTMENT
