5300477-UIM-A-0317
Johnson Controls Unitary Products
11
NOTES:
1. The pressure drop through the economizer is greater for 100% outdoor air
than for 100% return air. If the resistance of the return air duct is less than
0.25 IWG, the unit will deliver less CFM during full economizer operation.
Filter pressure drop based on standard filter media tested at velocities not to
exceed 300 ft/min.
SECTION VI: OPERATION
All PCE6 models contain a multi-stage compressor, therefore a multi-
stage thermostat must be used.
COOLING SEQUENCE OF OPERATION
1.
On a call for cooling, the wall thermostat sends a 24V “Y” signal to
the unit. The unit contactor closes, which energizes the outdoor fan
and the compressor. The indoor blower control board sends a signal
to the indoor blower motor which runs at the selected “LOW COOL”
cooling speed. A 24V signal from the room thermostat to the unit “Y2”
input operates the compressor at full capacity, and the indoor blower
control board operates the indoor blower at the “HIGH COOL” speed.
The unit does not operate on a second stage cooling call without a
call on the first stage “Y1” input.
2.
When the demand for cooling is satisfied, the wall thermostat
removes the 24V “Y” signal from the unit. The contactor opens, and
the outdoor fan and compressor stop. The indoor blower control
board continues to operate the indoor blower for 60 seconds after
the cooling signal is removed.
Dehumidification/Humidity Switch Input
This model unit features a built in de-humidification feature for
advanced dehumidification during cooling operation. The unit indoor
blower control is designed to work with a humidity control that closes
when the humidity is below the set-point. The control is open when the
humidity is above the set-point. This humidity control may be referred to
as a humidistat or dehumidistat.
To use this feature, the control HUM STAT jumper must be set to YES
and a humidistat is connected from the low voltage R and HUM color
coded leads. During cooling operation if the humidity level is above the
humidistat set point, the indoor blower speed is reduced by approxi-
mately 15%.
Safety Controls
The control circuit includes the following safety controls:
High Pressure Switch (HPS) -
The switch protects against excessive
discharge pressures.
Loss of Charge Switch (LCS) -
The switch protects against loss of
charge due to a leak in the system.
The above pressure switch is specifically designed to operate with R-
410A systems. R-22 pressure switches must not be used as replace-
ments for the R-410A pressure switch.
Indoor Circulating Blower
When the thermostat calls for “FAN,” the thermostat terminal “G” is
energized signaling the indoor blower control board to operate the cir-
culating blower to run continuously. The circulating blower airflow is
approximately 63% of the “HIGH COOL” airflow selected on the indoor
blower control board.
If a call for “COOL” occurs on “Y1,” the indoor blower runs at the “LOW
COOL” speed based on the “COOL” jumper setting. If a call for cool is
present on “Y1”+”Y2,” the indoor blower runs at the “HIGH COOL”
speed based on the “COOL” jumper setting.
If a call for “HEAT” occurs on “W1,” the circulating blower runs at the
heat speed based on the “HEAT” jumper setting. Note that there is only
one airflow stage and one electric heating stage available on 460V PCE
units (whether call is active on just “W1” or on both “W1” + “W2”).
When the thermostat ends the call for “FAN,” the thermostat terminal
“G” is de-energized, and the indoor blower control board stops the cir-
culating blower operation.
Table 10:
Additional Static Resistance
Size (Tons)
CFM
Wet Indoor Coil
Economizer
Filter/Frame Kit
36 (3.0)
700
0.01
0.00
0.04
800
0.02
0.01
0.06
900
0.03
0.01
0.08
1000
0.04
0.01
0.10
1100
0.05
0.01
0.13
1200
0.06
0.02
0.16
1300
0.07
0.03
0.17
1400
0.08
0.04
0.18
48 (4.0)
1100
0.02
0.02
0.04
1200
0.03
0.02
0.04
1300
0.04
0.02
0.05
1400
0.05
0.03
0.05
1500
0.06
0.04
0.06
1600
0.07
0.04
0.07
1700
0.07
0.04
0.08
1800
0.08
0.04
0.09
1900
0.09
0.05
0.10
2000
0.09
0.05
0.11
60 (5.0)
1100
0.02
0.02
0.04
1200
0.03
0.02
0.04
1300
0.04
0.02
0.05
1400
0.05
0.03
0.05
1500
0.06
0.04
0.06
1600
0.07
0.04
0.07
1700
0.07
0.04
0.08
1800
0.08
0.04
0.09
1900
0.09
0.05
0.10
2000
0.09
0.05
0.11
WARNING
The ability to properly perform maintenance on this equipment
requires certain expertise, mechanical skills, tools and equipment. If
you do not possess these, do not attempt to perform any mainte-
nance other than those procedures recommended in this Installation
Manual. Failure to heed this warning could result in serious injury
and possible damage to this equipment.
!
