TK 61552-2-MM-EN
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5.
Operate the unit on cool and pump down the low side to 20 in. Hg (-0.68 bar)of vacuum.
6.
Stop the unit. The condenser and suction pressures should remain stable, indicating no
leaks.
7.
Shift the three-way valve to the heat position. The low side gauge will raise slightly. The high
side gauge will drop to approximately zero. The gauges will equalize.
8.
The gauges will remain in this position, approximately zero, if the three-way valve seals
properly toward the condenser and the condenser pressure bypass check valve seals
properly.
9.
Back seat condenser pressure bypass check valve stem against the snap ring. Both gauges
should rise indicating the condenser pressure bypass check valve is properly releasing
condenser pressure into the discharge tube and evaporator.
10. Replace the cap on the condenser pressure bypass check valve.
N
No
otte
e:: Valve stem MUST be back seated during normal unit operation.
11. Open the receiver tank return outlet valve, remove the gauges and return the unit to normal
operation.
Electronic Throttling Valve (ETV)
The Electronic Throttling Valve (ETV) is standard on the these units. The ETV is a variable
position valve operated by a stepper motor. The ETV is located in the suction line between the
accumulator and the suction vibrasorber. The ETV system also uses discharge and suction
pressure transducers, and a hot gas bypass valve.
The ETV has two internal coils. The microprocessor operates the valve by energizing the coils
with a variable frequency AC signal. The valve position can be monitored with the Gauges Menu.
Zero (0) indicates the valve is fully closed and 800 indicates the valve is fully open.
The microprocessor tests the ETV if required when the unit is started. Alarm Code 89 indicates
the refrigeration system pressures did not respond as expected during the test. This may be
caused by a malfunction of the ETV or by a refrigeration system problem such as low refrigerant
level, a frozen expansion valve, or a restriction in suction line. The microprocessor ignores the
test results if the box temperature or the ambient temperature is below -12 C (10 F). The ETV test
can also be performed using the Service Test Mode.
Use the Gauges Menu to observe the ETV position during the ETV test. The expected ETV
position observation is a decrease followed by an increase. The suction pressure should
decrease when the valve position decreases and increase when the valve position increases.
Refer to the appropriate Diagnostic Manual for complete information about the testing and
operation of the ETV.
Refer to “Electronic Throttling Valve” in Refrigeration Service Operations for removal and
installation procedures.
