Operating Sequence; Base Unit Controls - Bryant Legacy 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 se-
lected as Automatic, the IFC will be energized on a call for
Cooling; indoor (supply) fan motor runs. When thermostat call
for Cooling is satisfied, the IFC is de-energized and indoor
(supply) fan motor stops.
COOLING, UNIT WITHOUT ECONOMIZER
569J***A/B (Single Circuit)
On a thermostat call for Cooling, IFC will be energized and in-
door (supply) fan motor runs. Thermostat output Y1 is ener-
gized; terminal Y1 at 569J***A/B unit receives 24-v. 24-v re-
ceived at CADM1 terminal Y. If anti-recycle time delay period
has not expired, CADM1 relay will remain open, de-energizing
Solenoid Valve Relay (SVR) and preventing compressor start.
When safety pressure switches are closed and CADM1 time
delay expires, CADM1 relay closes, SVR and compressor con-
tactor C1 are energized; liquid line solenoid valve LLSV
opens, all outdoor fan motors start and Compressor 1 starts.
As space cooling load is satisfied, thermostat output Y1 is de-
energized, removing 24-v at 569J***A/B terminal Y1. On Y1
opening, Compressor stops, all outdoor fan motors stop and
SVR relay is de-energized. Liquid line solenoid valve is
de-energized and valve closes. CADM1 begins its three-minute
anti-recycle time delay.
569J*07G/H or 569J*08G/H (Single Circuit/2-Stage)
On a thermostat call for Cooling, IFC will be energized and in-
door (supply) fan motor runs. Thermostat output Y1 is ener-
gized; terminal Y1 at either 569J*07G/H or 569J*08G/H unit re-
ceives 24-v. 24-v received at CADM1 terminal Y. If anti-recycle
time delay period has not expired, CADM1 relay will remain
open, de-energizing Solenoid Valve Relay (SVR) and preventing
compressor start. When safety pressure switches are closed and
CADM1 time delay expires, CADM1 relay closes, SVR and
compressor contactor C1are energized; liquid line solenoid valve
LLSV opens, all outdoor fan motors start and Compressor 1
starts.
On a thermostat calling for Stage 2 Cooling, thermostat output
Y2 is energized; terminal Y2 at either 569J*07G/H or
569J*08G/H units receive 24-v. 24-v received at CADM1
terminal Y2. CADM1 DC SOL terminal outputs 24-vdc to the
compressor loader plug (LDR) and the compressor operates at
full load capacity.
As space cooling load is satisfied, thermostat outputs Y2 and
Y1 are sequentially de-energized, removing 24-v at either
569J*07G/H or 569J*08G/H terminals Y2 and Y1. Compressor
loader plug is de-energized on Y2 opening. On Y1 opening,
Compressor 1 stops, all outdoor fan motors stop and SVR relay
is de-energized. Liquid line solenoid valve is de-energized and
valve closes. CADM1 begins its three-minute anti-recycle time
delay.
569J***D/E/F (Two Circuit)
On a thermostat call for Cooling, IFC will be energized and in-
door (supply) fan motor runs. Thermostat output Y1 is ener-
gized; terminal Y1 at 569J***D/E/F unit receives 24-v. 24-v
received at CADM1 terminal Y. If anti-recycle time delay peri-
od has not expired, CADM1 relay will remain open, de-ener-
gizing Solenoid Valve Relay 1 (SVR1) and preventing com-
pressor start. When safety pressure switches are closed and
CADM1 time delay expires, CADM1 relay closes, SVR1 and
compressor contactor C1 are energized; liquid line solenoid
valve LLSV1 opens, all outdoor fan motors start and Circuit 1
compressor starts.
On a thermostat calling for Stage 2 Cooling, thermostat output
Y2 is energized; terminal Y2 at 569J***D/E/F unit receives
24-v. 24-v received at CADM2 terminal Y. If anti-recycle time
delay period has not expired, CADM2 relay will remain open,
de-energizing Solenoid Valve Relay 2 (SVR2) and preventing
compressor start. When safety pressure switches are closed and
CADM2 time delay expires, CADM2 relay closes, SVR2 and
compressor contactor C2 are energized; liquid line solenoid
valve LLSV2 opens and Circuit 2 compressor starts.
As space cooling load is satisfied, thermostat outputs Y2 and
Y1 are de-energized, removing 24-v at 569J***D/E/F
terminals Y2 and Y1. Circuit 2 compressor stops on Y2 open-
ing; SVR2 is de-energized and LLSV2 closes. CADM2 begins
its three-minute anti-recycle time delay. On Y1 opening, Cir-
cuit 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. CADM1 begins its three-minute
anti-recycle time delay.
569J*12F, UNIT WITH HOT GAS BYPASS (HGBP)
Figure 30 illustrates the factory-installed hot gas bypass
(HGBP) option for 569J*12F units. See Fig. 31 for the location
of the Hot Gas Bypass. The HGBP is set at about 109 psig
(752 kPa) (about 36°F (2°C) saturation temperature), to main-
tain the evaporator coil temperatures above 36°F (2°C). The
liquid injection valve (TXV) is set at approximately 17°F (9°C)
superheat. The valves on the HGBP option are preset at the
factory, but may be adjusted in the field.
As the load on the indoor evaporator decreases, the suction pres-
sure will decrease which is detected by the HGBP valve
(constant pressure valve). When the suction pressure approaches
109 psig (752 kPa), the HGBP valve begins to open to allow hot
gas from the compressor to bypass to the suction pipe in a con-
trolled manner to attempt to maintain a constant suction pres-
sure. Since hot gas is too hot for entering the compressor, the de-
vice includes a liquid injector (or TXV) which feeds a little re-
frigerant from the liquid line through the TXV to de-superheat
the hot gas and maintain an acceptable refrigerant quality to not
damage the compressor. When hot gas bypasses, it reduces the
mass flow of refrigerant to the evaporator which reduces its ca-
pacity, and attempts to maintain the suction saturation tempera-
ture above 32°F (0°C) which minimizes the potential for freeze-
up in the evaporator coil.
The HGBP solenoid valve, as indicated in the lower left of Fig. 30,
allows HGBP control during first stage cooling operation.
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