5285473-UIM-E-1217
Johnson Controls Unitary Products
17
COOLING SEQUENCE OF OPERATIONS
When the thermostat calls for “COOL,” the thermostat terminals “G” and
“Y1” are energized, which signals the compressor, outdoor fan and
indoor blower to run on first stage cooling.
With a call for “Y1,” the circulating fan is energized at first stage cooling
speed.
The control cycles the compressor and indoor fan to second stage cool-
ing speed anytime a second stage cooling (Y2) call is received during a
first stage cooling (Y1) call. The control does not operate on second
stage cooling without a call on the “Y2” thermostat input.
When the thermostat is satisfied, terminals “G” and “Y” are de-ener-
gized, de-energizing the compressor and outdoor fan.
After a cool fan off delay timing of 30 seconds, the circulating fan is de-
energized.
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,” the AC / HP jumper must be set to “A/C,” 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 approximately 15%.
Safety Controls
The control circuit includes the following safety controls:
High Pressure Switch (HP) -
This switch protects against excessive
discharge pressures due to a blocked condenser coil or a condenser
motor failure (switch opens at 650 ±
25 psig and closes at 450 ±
25
psig).
Low Charge Switch (LCS) -
The switch protects against loss of charge
due to a leak in the system.
The high 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 switches.
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 “W1” or “W1”+“W2”, the circulating blower
runs at the heat speed based on the “HEAT” jumper setting.
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.
Delay Profiles
The Delay Profiles are shown in Table 15 for each Delay jumper setting.
The levels shown in the Pre-Run, Short-Run, and Run Periods are a
percentage of the blower speed corresponding to the thermostat call.
The Post-Run and Off Delay levels are derived from the level of the pre-
vious state, not the blower speed corresponding to the thermostat call.
If in Delay Profile B and in the Short-Run Period (82% of capacity) and
the thermostat call is removed, this causes the control to enter the Post-
Run state. The Post-Run state level for Delay Profile B is 100% of the
previous level, so the level during the Post-Run state is 82%.
Table 13:
Ignition Control Board Flash Codes
Flash Code
Description
Normal Operation
Green Heartbeat
Standby mode
Amber Heartbeat
Call for furnace heat active
Operational Faults
Steady ON (any color) Control failure
Rapid Amber Flashes
Low flame current
1 Red Flash
Flame sensed with gas valve off
2 Red Flashes
Pressure switch closed with inducer off
3 Red Flashes
Pressure switch open with inducer on
4 Red Flashes
Limit switch or rollout switch open
5 Red Flashes
Limit switch or rollout switch open greater than
15 minutes
6 Red Flashes
Pressure switch cycle lockout
7 Red Flashes
Lockout due to failed ignition
8 Red Flashes
Lockout due to too many flame dropouts
10 Red Flashes
Gas valve fault code
11 Red Flashes
Limit/Rollout switch open between 5 and 15
minutes
12 Red Flashes
Model plug not inserted
Wiring Related Faults
9 Red Flashes
Incorrect line voltage polarity
4 Amber Flashes
Y
thermostat demand without a G
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.
!
TABLE 14 : Delay Profile Descriptions
Delay
Profile
Period
Cooling
Level%
Time in State
(Minutes)
A
Pre-Run
Bypass
Bypass
Short-Run
Bypass
Bypass
Run
100
No Limit
Post-Run*
100
1
Off Delay*
Bypass
Bypass
B
Pre-Run
50
2
Short-Run
82
5
Run
100
No Limit
Post-Run*
100
1
Off Delay*
Bypass
Bypass
C
Pre-Run
Bypass
Bypass
Short-Run
Bypass
Bypass
Run
100
No Limit
Post-Run*
100
1
Off Delay*
50
1
D
Pre-Run
Bypass
Bypass
Short-Run
63
1.55
Run
100
No Limit
Post-Run*
100
1
Off Delay*
63
0.5
