Refrigeration Maintenance (Rev 6/98)
79
5.
Place fuse F31 back in the relay board. The suction
pressure should drop 69 to 138 kPa (10 to 20 psi). If the
suction pressure does not drop, check the modulation
valve and the associated circuitry.
HOT GAS SOLENOID VALVE (HG)
The hot gas solenoid valve (HG) is used in conjunction with
the modulation valve to reduce the capacity of the unit dur-
ing modulation. This normally closed solenoid valve is
located in the refrigeration line that connects the discharge
line to the hot gas line. The HG valve is energized (opened)
at full modulation. The HG valve is de-energized (closed)
when modulation is discontinued.
Hot Gas Solenoid Valve Test
1.
Check the electrical circuit by running a full Unit Self
Check.
2.
Pump down the low side with the unit running in cool
and the setpoint at least 5.6° C (10° F) below the return
air temperature.
If the low side pumps down, the HG is closed and is not
leaking.
If the low side will not pump down, diagnose the prob-
lem using the procedures in Diagnosing Thermo King
Refrigeration Systems TK 5984-7. Do not prematurely
assume that the HG is faulty if the low side will not
pump down.
3.
With the low side in a vacuum, disconnect the connec-
tor that connects the HGS and HGG wires to the main
wire harness. Use jumpers to energize the HG by apply-
ing 12 volts to the HGS wire and grounding the HGG
wire.
If the pressure in the low side rises, the HG is opening.
If the pressure in the low side does not rise, the HG is
not opening. Perform further diagnosis using the
procedures in Diagnosing Thermo King Refrigeration
Systems TK 5984-7.
4.
Reconnect the HGS and HGG wires to the main wire
harness before returning the unit to service.
See the Refrigeration Service Operations chapter of this
manual for removal and installation procedures.
THERMAX-V SYSTEM (TF+ ONLY)
The Thermax-V system differs from the standard 3-way
valve system only in the method by which the liquid refrig-
erant is metered into the heat/defrost circuit. The Thermax-
V system uses an expansion valve to meter liquid refriger-
ant into the suction line when the unit is in the heat/defrost
cycle.
Thermax-V Operation
When in the cool cycle (see page 82) the Thermax-V expan-
sion valve (item 33) will be closed because of the cool suc-
tion line. The unit operates the same as a standard unit.
NOTE: The Thermax-V expansion valve does not have a
bleed port in it.
When in the heat/defrost cycle the Thermax-V expansion
valve will be open because of the warm suction line. It will
remain open until the suction line pressure rises enough to
overcome the power element force. When the Thermax-V
expansion valve is open, refrigerant will be pulled out of the
receiver tank and condenser because of the lower pressure
in the low side. The Thermax-V system accurately controls
the amount of refrigerant in the heat/defrost cycle and deliv-
ers consistent heat/defrost capacity under all ambient condi-
tions.
Summary of Contents for Super II SR+
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Page 22: ...Unit Description Rev 6 98 12 Front View AEA1350 ...
Page 23: ...Unit Description Rev 6 98 13 Right Side Door Open AEA1351 ...
Page 24: ...Unit Description Rev 6 98 14 Left Side Doors Open AEA1352 ...
Page 26: ...Operating Instructions Rev 6 98 16 Control Box Cover AEA1354 ...
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Page 42: ...Electronic Controls Rev 6 98 32 SOFTWARE REVISION 04XX ALARMS AEA1358 ...
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Page 141: ...131 Schematic Diagram SBIII SII RMNII 30 SR MPIV ...
Page 142: ...132 Wiring Diagram SII SBIII RMN30 SR MPIV Page 1 of 4 ...
Page 143: ...133 Wiring Diagram SII SBIII RMN30 SR MPIV Page 2 of 4 ...
Page 144: ...134 Wiring Diagram SII SBIII RMN30 SR MPIV Page 3 of 4 ...
Page 145: ...135 Wiring Diagram SII SBIII RMN30 SR MPIV page 4 of 4 ...