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OPERATING SEQUENCE
Base Unit Controls
INDOOR (SUPPLY) FAN
If the thermostat fan operation is selected as Continuous, then
the indoor (supply) fan motor, which is remotely located in the
fan coil, runs continuously. If the thermostat fan operation is
selected as Automatic, then the indoor (supply) fan motor runs
when there is a call for Cooing or Heating. When thermostat is
satisfied, the indoor (supply) fan motor stops. If there is a fan
fault or a shutdown condition in the fan coil, then the indoor
(supply) fan will not run if there is a call for ventilation, cool-
ing, or heating and the 575J unit will act as if it is not receiving
a cooling or heating demand.
COOLING, UNIT WITHOUT ECONOMIZER
When thermostat calls for Cooling, terminal Y1 is energized.
The 575J's Defrost Board (DFB) receives this input at P2-5.
DFB issues 24-v outputs at OF, P3-7 (RVS1) and P3-10
(COMP1). The OF output energizes outdoor fan relay (OFR);
all outdoor fan motors start and run, subject to ambient tem-
perature (refer to Fan Cycling section). The output RVS1 ener-
gizes the reversing valve solenoid 1 (RVS1); Reversing Valve
1 switches to Cooling position.
Compressor Lockout Relay (CLR) is energized, closing its nor-
mally open contacts and allowing the Defrost Board to accept a
Y2 thermostat signal. Loader Control Relay (LCR) is also en-
ergized, closing its contacts between terminals 2 and 4 and al-
lowing the compressor loader to get energized once the Defrost
Board receives a Y3 thermostat signal.
Output P3-10 (COMP1, 24-v) is received at CADM1 terminal
Y. If anti-recycle time delay period has not expired, safety
pressure switches are open, and/or lockout alarms are active,
then CADM1 relay will remain open, preventing compressor
start. When safety pressure switches are closed and CADM1
time delay expires, the CADM1 relay closes, energizing Sole-
noid Valve Relay SVR1 and compressor contactor C1. SVR1
contacts close, energizing the external liquid line solenoid
valve. Solenoid valve LLSV1 opens. Compressor contactor C1
closes, energizing the compressor motor. Compressor 1 starts
and system runs in Cooling mode.
On a thermostat call for Stage 2 Cooling, terminal Y2 is ener-
gized; 24-v passes through CLR normally open contacts (ter-
minals 2 and 4) and the Defrost Board receives this input at
P2-4. DFB issues 24-v at P3-6 (RVS2) and P3-8 (COMP2).
Output P3-6 energizes Reversing Valve Solenoid 2 (RVS2);
Reversing Valve 2 switches to Cooling position. Output PL3-8
is received at CADM2 terminal Y. If anti-recycle time delay
period has not expired, safety pressure switches on Circuit 2
are open, and/or lockout alarms are active, then CADM2 relay
will remain open, preventing Compressor 2 start. When safety
pressure switches are closed and CADM2 time delay expires,
CADM2 relay closes, energizing Solenoid Valve Relay 2
(SVR2) and compressor contactor C2. SVR2 contacts close,
energizing the external Liquid Line Solenoid Valve 2 (LLSV2).
LLSV2 opens. Compressor contactor C2 closes, energizing the
compressor motor on COMP2. Compressor 2 starts and the
system runs in second-stage cooling mode.
On a thermostat call for Stage 3 Cooling, terminal X (Y3) is
energized. 24-v passes through LCR normally open contacts
(terminals 2 and 4) and enters CADM1-Y2. CADM1 DC SOL
terminal outputs 24-vdc to the compressor loader plug (LDR)
and Compressor 1 operates at full capacity.
As space cooling load is satisfied, thermostat outputs Y3, Y2,
and Y1 are sequentially de-energized, removing 24-v at 575J
terminals X (Y3), Y2, and Y1. Compressor 1 loader plug is de-
energized on Y3 opening. Circuit 2 compressor stops on Y2
opening; SVR2 is de-energized and LLSV2 closes, and
CADM2 begins its three-minute anti-recycle time delay. On
Y1 opening, Circuit 1 compressor stops, all outdoor fan motors
stop, and SVR1 relay is de-energized. Liquid line solenoid
valve LLSV1 is de-energized and valve closes. Compressor
Lockout Relay and Loader Control Relay are de-energized.
CADM1 begins its three-minute anti-recycle time delay.
If either the Loss of Charge (LOC) Switch or High Pressure
Switch (HPS) on either circuit opens while Y1, Y2, or Y3 re-
main energized, then the compressor contactor C and relay
SVR on the corresponding circuit are de-energized; compres-
sor stops and liquid line solenoid is de-energized (valve clos-
es). Corresponding CADM initiates a TRIP event (cooling de-
mand sensed at CADM terminal Y but no current is measured
at T1, T2, T3 motor sensors); CADM relay opens and RED
LED is illuminated. TRIP condition maintains lockout of com-
pressor operation until CADM is manually reset. Reset CADM
by cycling unit main power.
Reversing valve solenoid (RVS) is energized in Cooling
modes. This solenoid will remain energized until the next
Heating mode is initiated.
COOLING, UNIT WITH ECONOMIZER
Refer to fan coil unit installation instructions and economizer
accessory installation instructions for operating sequences
when system is equipped with accessory economizer.
HEATING
When the thermostat calls for first stage heating, terminal W1
is energized. The 575J's Defrost Board (DFB) receives this in-
put at P2-7. The DFB removes the output at P3-7 (RVS1) and
P3-6 (RVS2); the reversing valve solenoids are de-energized
and the reversing valves move to Heating position.
DFB issues outputs at OF, P3-10 (COMP1), and P3-8
(COMP2). Outdoor fan relay OFR is energized; all outdoor fan
motors run.
Outputs P3-10 (COMP1, 24-v) is received at CADM1 terminal
Y and P3-8 (COMP2, 24-v) is received at CADM2 terminal Y.
If anti-recycle time delay period has not expired and/or safety
pressure switches are open on a particular circuit, then outdoor
lockout alarms are active and corresponding CADM relay will
remain open, preventing compressor start. When safety
pressure switches are closed and CADM1 and 2 time delay ex-
pires, the CADM 1 and 2 relay closes, energizing Solenoid
Valve Relays SVR1 and 2 and compressor contactors C1 and
C2. SVR1 and 2 contacts close, energizing the external liquid
line solenoid valves. Solenoid valves LLSV1 and LLSV2
open. Compressor contactors C1 and C2 close, energizing the
compressor motors. 24-v is also received at CADM1 terminal
Y2 through the Loader Control Relay (LCR) normally closed
terminals 3 and 4. CADM1 DC SOL terminal outputs 24-vdc
to the compressor loader plug (LDR). Compressors start, run-
ning at full capacity, and system runs in Heating mode, provid-
ing Stage 1 Heat.
When the space heating load is satisfied terminal W1 is de-
energized. Compressors and outdoor fan operations stop. Liq-
uid line solenoid LLSV is de-energized and valve closes.
CADM begins its three-minute anti-recycle time delay.
If either the Loss of Charge (LOC) Switch or High Pressure
Switch (HPS) on either circuit opens while W1 remains ener-
gized, then the compressor contactor C and relay SVR on the
corresponding circuit are de-energized; compressor stops and
liquid line solenoid is de-energized (valve closes). Correspond-
ing CADM initiates a TRIP event (compressor demand sensed
at CADM terminal Y but no current is measured at T1, T2, T3
motor sensors); CADM relay opens and RED LED is illumi-
nated. TRIP condition maintains lockout of compressor opera-
tion until CADM is manually reset. Reset CADM by cycling
unit main power.
Reversing valve solenoid remains de-energized until the next
Cooling cycle is initiated.
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