5750156-UIM-B-0919
Johnson Controls Ducted Systems
19
4.
After the manifold pressure has been adjusted, re-calculate the fur-
nace input to make sure you have not exceeded the specified input
on the rating plate. See Natural Gas in the CHECKING GAS HEAT
INPUT section.
5.
Once the correct BTU (kW) input has been established, turn the
gas valve to OFF and turn the electrical supply switch to OFF.
Remove the flexible tubing from the gas valve pressure tap and
tighten the pressure tap plug using the 3/32 in. (2.4 mm) hex head
wrench.
6.
Turn the electrical and gas supplies back on, and with the burners
in operation, check for gas leakage around the gas valve pressure
port using an approved non-corrosive gas leak detection fluid, or
other non-flammable leak detection methods.
AIRFLOW SETTINGS
Cooling Airflow Settings
This unit is equipped with a five-speed blower motor. Select the
required cooling airflow by connecting the required motor speed tap
wire to the yellow Cool speed wire coming from the control board.
Select the speed to deliver approximately 350 CFM to 400 CFM per ton
of A/C cooling capacity. Use of airflow outside of this range may cause
diminished air conditioning performance, lower overall energy effi-
ciency, and higher electric utility bills. See Table 18 for default cooling
blower settings.
Continuous Fan Airflow Settings
The default blower speed for continuous fan operation is Low speed. To
operate the furnace in continuous fan mode, set the wall thermostat
Fan switch to On. To select the required continuous fan airflow, connect
the required motor speed tap wire to the red Fan Speed wire coming
from the control board.
The default position is with the red (Low) blower speed wire connected
to the red Fan Speed wire coming from the control board. In certain cir-
cumstances, it may be necessary to move the continuous fan speed to
a different speed tap. However, this is not best practice because it
causes higher electrical energy usage and higher electric utility bills.
Gas Heating Airflow Settings
See Table 18 for the default heating blower speed. The unit is equipped
with a five-speed blower motor. See Table 18 for the default heating
blower speed for each model.
In certain circumstances, it may be necessary to move the heating
blower speed to a different motor speed tap. Not all of the five motor
speeds are appropriate for gas heating operation. The use of heating
airflow at a speed other than the default speed causes diminished heat-
ing performance and may cause the furnace temperature limit controls
to shut down the furnace.
Measurement of Temperature Rise
FIGURE 9:
Gas Valve
IMPORTANT:
If gas valve regulator is turned in (clockwise), manifold
pressure is increased. If screw is turned out (counterclockwise), man-
ifold pressure will decrease.
MANIFOLD PRESSURE “U” TUBE CONNECTION
FIGURE 10:
Reading Gas Pressure
INLET
WRENCH
BOSS
INLET
PRESSURE
PORT
ON
OFF
ON/OFF SWITCH
(Shown in ON position)
MAIN REGULATOR
ADJUSTMENT
OUTLET
OUTLET
PRESSURE
PORT
VENT PORT
A0226-001
287/(7
35(6685(3257
*$69$/9(
´78%,1*
0$1,)2/'
3,3(
*$6
%851(56
878%(
0$120(7(5
,1
:$7(5
&2/801
*$6
35(6685(
6+2:1
$
)/$0(
6(1625
Table 18:
Default Blower Speeds
Model Number
Default Blower Speeds
Heat
(White Wire)
Cool
(Yellow Wire)
Continuous Fan
(Red Wire)
PCG4A24050
Low (1)
High (5)
Low (1)
PCG4A24075
Medium (3)
High (5)
Low (1)
PCG4A30050
Low (1)
High (5)
Low (1)
PCG4A30075
Medium Low (2)
High (5)
Low (1)
PCG4A36050
Low (1)
High (5)
Low (1)
PCG4A36075
Medium Low (2)
High (5)
Low (1)
PCG4A36100
Medium (3)
High (5)
Low (1)
PCG4A42075
Low (1)
High (5)
Low (1)
PCG4A42100
Medium (3)
High (5)
Low (1)
PCG4B48065
Medium Low (2)
High (5)
Low (1)
PCG4B48100
Medium Low (2)
High (5)
Low (1)
PCG4B48125
Medium Low (2)
High (5)
Low (1)
PCG4B60065
Low (1)
High (5)
Low (1)
PCG4B60100
Low (1)
High (5)
Low (1)
PCG4B60125
Medium Low (2)
High (5)
Low (1)
DANGER
The temperature rise, or temperature difference between the return
air and the supply (heated) air from the furnace, must be within the
range shown on the furnace rating plate and within the application
limitations shown in Table 7.
The supply air temperature cannot exceed the “Maximum Supply
Air Temperature” specified in these instructions and on the furnace
rating plate. Under NO circumstances can the furnace be allowed to
operate above the Maximum Supply Air Temperature. Operating the
furnace above the Maximum Supply Air Temperature will cause pre-
mature heat exchanger failure, high levels of Carbon Monoxide, a fire
hazard, personal injury, property damage, and/or death.
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