650.75-N4U
035-14370-000
30
Unitary Products Group
3.
Refer to Figure 36 on page 28, for location of pressure
regulator adjustment cap and screw on main gas valve.
4.
Turn gas and electrical supplies ON. Start furnace and
observe manifold pressure on manometer.
5.
Adjust manifold pressure by adjusting gas valve regula-
tor screw for the appropriate gas per the following:.
If gas valve regulator is turned in, or clockwise, manifold
pressure is increased. If screw is turned out, or counterclock-
wise, manifold pressure will decrease.
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. Application limi-
tations are shown in Table 1 or 2. After the temperature rise
has been determined, the cfm can be calculated.
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.
All direct-drive blowers have multi-speed motors. The blower
motor speed taps are located in the control box in the blower
compartment. Refer to Figure 37, and the unit wiring label to
change the blower speed.
You may select a heating speed and a cooling speed. They
may be the same speed or a different speed.To use the same
speed tap for heating and cooling, the heat terminal and cool
terminal must be connected using a jumper wire and con-
nected to the desired motor lead. Place all unused motor
leads on Park terminals. Two Park terminals are provided. .
ADJUSTMENT OF FAN-OFF CONTROL SETTINGS
This furnace is equipped with a time-on/time-off heating fan
control. The fan on is fixed at 30 seconds. The fan off is field
adjustable from 60 to 180 seconds. The fan off is factory set
to 60 seconds. Adjust the off time by repositioning the fan off
switches. (Refer to Figure 37.)
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 setting
the option switches located (Refer to Figure 37) on the con-
trol board as follows:
Natural Gas ..............................................................3.5” W.C.
Propane (LP) Gas ....................................................10.0” W.C.
If manifold pressure is too high, an over-fire condi-
tion exists which could cause heat exchanger fail-
ure. If the manifold pressure is too low, sooting
and eventual clogging of the heat exchanger could
occur.
Once the correct gas pressure to the burners has
been established, turn the gas valve knob to OFF
and turn the electrical supply switch to OFF; then
remove the pressure tap at the gas valve and re-
install the plug, using a compound (on the threads)
resistant to the action of LP gases. Replace the
burner box front cover or the pressure reference
hose.
Be sure that gas valve regulator cap and burner
box to gas valve pressure reference hose is recon-
nected.
Do not energize more than one motor speed at a
time or damage to the motor will result.
FIGURE 37 : TYPICAL HEAT/COOL SPEED TAP
CONNECTIONS
To Delay Fan-Off
By:
Set Switch
1
2
60 Sec.
ON
ON
90 Sec.
OFF
ON
120 Sec.
ON
OFF
180 Sec.
OFF
OFF
