Thermo King 098203, Руководство по обслуживанию

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Operating Theory
135
Economizer System
An economizer heat exchange system replaces the conventional heat exchanger. The economizer system
subcools the liquid refrigerant before it reaches the evaporator expansion valve. Subcooling liquid
refrigerant increases the cooling efficiency and capacity of the evaporator.
Figure 105: Economizer Heat Exchanger
A vapor injection line tee is located in the liquid line between the filter drier/in-line filter and the
economizer heat exchanger. A vapor injection valve controls refrigerant flow through the vapor injection
line to the economizer expansion valve. When this normally closed valve is energized (open), a portion of
liquid refrigerant flows through the economizer expansion valve and evaporates in the inner coiled tube
of the economizer. This cools the rest of the liquid refrigerant that flows past the tee and through the
economizer to the evaporator coil.
The economizer suction gas continues through the vapor injection circuit and returns to the intermediate
suction port of the scroll compressor. Injecting the economizer suction gas into the compressor
downstream from the suction port prevents the gas from affecting the suction pressure or cooling capacity
of the evaporator coil. However, the economizer suction gas adds its heat and volume to the condenser
side of the refrigeration system, increasing the discharge pressure.
Because the economizer system increases system cooling capacity, the vapor injection valve is energized
(open) continuously when the compressor duty cycle (ON time) is 100 percent (Full Cool). High
compressor discharge temperature may cause the vapor injection valve to energize (open) but only while
the Compressor Digital Control valve is not energized (closed).
Data Recording and Downloading Data
The MP-4000 data logger can record sensor temperatures as well as loss of power, alarms, sensor failure,
setpoint change and unit shutdown events. All data logs include the time and date; setpoint temperature;
supply, return, ambient, USDA1, USDA2, USDA3 and cargo sensor temperatures; and humidity sensor.
All temperature logs can be viewed from the controller’s VGA message display.
Data logging intervals are selectable for 30 minutes, 1, 2 or 4 hours.
When a 1 hour logging interval is selected, the data logger memory can store approximately 680 days of
information. The logging of USDA sensors is fixed at 1 hour intervals to comply with USDA
requirements. A logging test of USDA sensors at 1 minute intervals is possible for 72 minutes. USDA
data can not be downloaded during the logging test and can only be viewed on screen. After 72 minutes,
controller returns to previous logging interval and clears USDA test data from data logger memory.
If the unit power supply is disconnected, the data logger will continue to register 120 temperature logs
(except humidity sensor) when battery voltage is above 4.2 volts. These will be maintained until the unit
is re-connected to power, and the battery automatically recharged.
AXA0427