5156631-UIM-G-0417
Johnson Controls Unitary Products
11
SECTION VIII: SYSTEM START-UP
ENERGIZE CRANKCASE HEATER
The control continually monitors the operation of the compressor. If the
outdoor ambient temperature is below 55°
F for 30 seconds continually
while the compressor is off for 20 minutes, the control cycles the crank-
case heater on for 10 minutes and off for 10 minutes until the outdoor
ambient temperature is above 55°
F for 30 seconds continually or the
compressor speed reference is greater than zero.
SECTION IX: SYSTEM OPERATION
ANTI SHORT-CYCLE DELAY
The control includes a five-minute anti short-cycle delay (ASCD) timer
to prevent the compressor from short-cycling after a power or thermo-
stat signal interruption. The ASCD timer is applied when the control is
first powered from the indoor unit thermostat and immediately following
the completion of a compressor run cycle. The compressor and the out-
door fan will not operate during the five minutes that the timer is active.
The ASCD timer can be bypassed by shorting the TEST terminals for 2-
5 seconds while the thermostat is calling for compressor operation (Y
input signal energized).
LOW VOLTAGE DETECTION
The control monitors the transformer secondary (24 VAC) voltage and
provides low voltage protection for the heat pump and its components.
In particular, the control prevents contactor chatter during low voltage
conditions. If the voltage drops below approximately 19 VAC, the con-
trol continues to energize any relays that are already energized, but the
control can no longer energize any additional relays until the voltage
level increases. If the voltage drops below approximately 16 VAC, the
control immediately de-energizes the relay outputs and can no longer
energize any relays until the voltage level increases. The control stores
and displays the appropriate fault codes when low voltage conditions
occur.
TEST INPUT
The control includes a TEST input connector that can be used for vari-
ous testing functions during installation and service. The TEST input
connector is shown in Figure 15. The following table summarizes the
behavior of the control when the two TEST pins are connected. More
detailed descriptions of the various functions are included in other sec-
tions of this document.
FIGURE 13:
Typical Field Wiring (Air Handler / Electrical Heat) (Single-Phase)
G
O
Y1
W
Y2
THERMOSTAT
A
0509-001
G
O
Y1
W1
W2
Y2
C
R
O
Y1
W
Y2
Y2
Out
W1
Out
W2
Out
IN
VERTER
IN
TER
F
ACE
CO
N
TRO
L
OUTDOOR
U
NI
T
IN
DOOR
U
NI
T
C
C
R
R
CAUTION
An attempt to start the compressor without at least 2 hours of crank-
case heat will damage the compressor.
When replacing the CCH, use the same 30 Watt CCH model which
originally came with the unit.
!
IMPORTANT
When connecting low voltage system wiring, DO NOT connect termi-
nal W to terminal W1 OUT and/or terminal W2 OUT. It can result in
causing auxiliary or backup heat to lock on.
TABLE 4:
TEST Input Functionality with Y
Duration of connection (seconds)
Control behavior with thermostat signals present
Less than 2
No response
2 – 5
Bypass ASCD (Reduce timer to zero immediately). If “Y1” is present and the high-pressure switch is
closed, the compressor is activated.
Clear Pressure Switch Lockout, and reset the 6 hour PS timer.
Greater than 5
Initiate defrost cycle ignoring the COIL temp, and record that defrost cycle was initiated by TEST short.
Defrost cycle is not initiated if “O” is present. Energize “W OUT,” and begin defrost cycle immediately upon
expiration of timer.
Test Pin Short removed
Terminate defrost as normal.
Test pin Short not removed
Continue defrost cycle until TEST connection removed.
