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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; 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
indoor (supply) fan motor runs. Thermostat output Y1 is
energized; terminal Y1 at 569J***A/B unit receives 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 C1 are energized;
liquid line solenoid valve LLSV opens, all outdoor fan
motors start and Compressor 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 (Single Circuit/ 2- - Stage)
On a thermostat call for Cooling, IFC will be energized and
indoor (supply) fan motor runs. Thermostat output Y1 is
energized; terminal Y1 at 569J*07G/H unit receives 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 569J*07G/H unit
receives 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
569J*07G/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
indoor (supply) fan motor runs. Thermostat output Y1 is
energized; terminal Y1 at 569J***D/E/F unit receives 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 1 (SVR1) and
preventing compressor 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
opening; SVR2 is de-energized and LLSV2 closes. 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. CADM1
begins its three-minute anti-recycle time delay.
569J*12F, Unit with Hot Gas Bypass (HGBP) —
Fig. 32 (on page 38) illustrates the factory- - installed hot gas
bypass (HGBP) option for 569J*12F units. The HGBP is set
at about 109 psig (752 kPa) (about 36_F (2_C) saturation
temperature), to maintain 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
pressure 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 controlled manner to attempt to maintain a
constant suction pressure. Since hot gas is too hot for
entering the compressor, the device includes a liquid injector
(or TXV) which feeds a little refrigerant 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
capacity, and attempts to maintain the suction saturation
temperature 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. 32, allows HGBP control during first stage cooling
operation.
37
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