Operating Sequence; Indoor (Supply) Fan; Cooling Unit Without Economizer; Cooling Unit With Economizer - Bryant 575Jx08G/H Series Installation, Start-Up And Service Instructions Manual

OPERATING SEQUENCE

Base Unit Controls
Indoor (Supply) Fan —
The indoor fan contactor (IFC) is remotely located at the
fan coil or fan section. If the thermostat fan operation is
selected as Continuous, the IFC is energized and the
indoor (supply) fan motor runs continuously. If the
thermostat fan operation is selected as Automatic, the IFC
will be energized on a call for Cooling or Heating; indoor
(supply) fan motor runs. When thermostat is satisfied, the
IFC is de-energized and indoor (supply) fan motor stops.
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); both outdoor fan motors start
and run. The output RVS1 energizes the reversing valve
solenoid (RVS); Reversing valve switches to Cooling
position.
Output PL3-10 (COMP1, 24-v) is received at CADM
terminal Y. If anti-recycle time delay period has not
expired, safety pressure switches are open, and/or lockout
alarms are active, CADM relay will remain open,
preventing compressor start. When safety pressure
switches are closed and CADM time delay expires, the
CADM relay closes, SVR and compressor contactor C1
are energized; Compressor Relay Timer (CTR) is closed
and Digital Cycle Timer (CTD) is energized commanding
Digital Compressor Solenoid (DCS) on, liquid line
solenoid valve LLSV opens, all outdoor fan motors start
and Compressor starts part load operation.
On thermostat call for Stage 2 Cooling, thermostat output
Y2 is energized CTR receives 24- - v at terminal 1 changing
contacts to open. CTD is de- - energized and commands
DCS off, Compressor operates at full load.
As space cooling load is satisfied, thermostat outputs Y2
and Y1 are sequentially de- - energized, removing 24- - v at
575J terminals Y1 and Y2. Compressor resumes part load
operation on Y2 opening. On Y1 opening, Compressor 1
stops, all outdoor fan motors stop and SVR is
de- - energized. Liquid Line solenoid valve is de- - energized
and valve closes. CADM1 begins its three- - minute
anti- - recycle time delay.
If either the Loss of Charge (LOC) Switch or High
Pressure Switch (HPS) opens while Y1 remains energized,
the compressor contactor C and relay SVR are
de-energized; compressor stops and liquid line solenoid is
de-energized (valve closes). CADM initiates a TRIP event
(cooling demand 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 compressor 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
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 input at P2-7. The DFB removes the output
at P3-7 (RVS1); the reversing valve solenoid is
de-energized and the reversing valve moves to Heating
position.
DFB issues outputs at OF and P3-10 (COMP1). Outdoor
fan relay OFR is energized; both outdoor fan motors run.
Output PL3-10 (COMP1, 24-v) is received at CADM
terminal Y. If anti-recycle time delay period has not
expired, safety pressure switches are open, and/or lockout
alarms are active, CADM relay will remain open,
preventing compressor start. When safety pressure switches
are closed and CADM time delay expires, the CADM relay
closes, energizing Solenoid Valve Relay SVR and
compressor contactor C. SVR contacts close, energizing the
external liquid line solenoid valve. Solenoid valve LLSV
opens. Compressor contactor C closes, energizing the
compressor motor. Compressor starts and system runs in
Heating mode, providing Stage 1 Heat.
When the space heating load is satisfied terminal W1 is
de-energized. Compressor and outdoor fan operations stop.
Liquid 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) opens while, the compressor
contactor C and relay SVR are de-energized; compressor
stops and liquid line solenoid is de-energized (valve
closes). 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 illuminated. TRIP condition
maintains lockout of compressor operation 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.
Defrost Cycle —
During the Heating Mode, frost and ice can develop on
the outdoor coil. Defrost sequence will clear the frost and
ice from the coil by briefly reversing the Heating
sequence periodically.
A window to test for a need to run the Defrost cycle opens
at a fixed period after the end of the last Defrost cycle or
the previous test window closed. The window period is
determined by the configuration settings on the DFB's
DIP switches (see unit wiring diagram).
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