System Operation
IMPORTANT
Some scroll compressor have internal vacuum protector that will unload scrolls when suction pressure goes below 20 psig. A hissing sound will be heard when the compressor is running unloaded. Protector will reset when low pressure in system is raised above 40 psig. DO NOT REPLACE COMPRESSOR.
This section addresses:
SUnit components (sensors, temperature switch, pressure switches and demand defrost control)
SSecond−stage operation
UNIT COMPONENTS
Demand Defrost Control (A108)
The demand defrost control measures differential temperatures to detect when the system is performing poorly because of ice build−up on the outdoor coil. The controller self−calibrates when the defrost system starts and after each system defrost cycle. The demand defrost control’s: components are shown in figure 25.
SDemand defrost control connections, jumpers and LED locations are shown in figure 25.
SDemand defrost control connections, jumpers and LED descriptions are listed on table 9.
SDemand defrost control status, fault and lockout LEDs are listed in table 10.
TEST PINS (P1)
DEFROST TERMINATION PIN SETTINGS (P1)
SENSOR PLUG IN (COIL AND AMBIENT SENSORS) (P4)
DELAY PINS (P5)
REVERSING VALVE (O OUT)
PRESSURE SWITCH CIRCUIT CONNECTIONS
LOW AMBIENT |
THERMOSTAT PINS |
(P3) |
DIAGNOSTIC LEDS |
(DS1 AND DS2) |
24V TERMINAL STRIP |
CONNECTIONS (P2) |
Note − Component locations vary by board manufacturer.
Figure 25. Demand Defrost Control (A108)
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