When hooking a vacuum pump to a refrigeration system,
it is important to connect the pump to both the high and
low side of the system.
Follow the pump manufacturer’s directions as to the
proper methods of using the vacuum pump .
The lines used to connect the pump to the system should
be copper and of the largest diameter that can pratically
be used. Using larger line sizes with minimum flow
resistance can significantly reduce evacuation time.
Rubber or synthetic hoses are not acceptable for unit
evacuation because they have moisture absorbing
characteristics which result in excessive rates of
outgassing and pressure rise during standing vacuum
test. This makes it impossible to determine if the unit has
a leak.
An electronic thermopile vacuum gauge should be installed
in the common line ahead of the vacuum pump shutoff
valve as shown in Figure 2. Close Valve B and open
Valve A. After several minutes, the gauge reading will
indicate the minimum blank-off pressure the pump is
capable of pulling . Rotary pump should produce vacuum
of less than 100 microns.
Open Valve B and evacuate the system to a pressure of
500 microns or less. Valve A must be closed when taking
this reading. Once 500 microns or less is obtained, with
Valve A closed, a time versus pressure rise should be
performed. The maximum allowable rise over a 15 minute
period is 200 microns. If pressure rise is greater than
200 microns but levels off to a constant value, excessive
moisture is present. If the pressure steadily continues to
rise, a leak is indicated.
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Figure 2
Vacuum pump connection.
Electrical Connections
Wiring diagrams are furnished with the units, but extra
copies may be obtained from the local Trane sales office.
The installing contractor is to provide and install fused
disconnect switches and the wiring up to the unit control
panel. Check all wiring connections and trace the circuits
to make sure that they agree with the wiring diagrams.
Caution :
1. All wiring should comply with local and national
codes. Type and location of disconnect switches
should comply with local and national codes. Install
disconnect switch near unit, within sight, for safety.
2. Use copper conductors only for installation wiring.
Unit terminals are not designed to accept other type
of wiring. The use of aluminium wire may cause
galvanic corrosion and/or overheating at the
connection points with resultant equipment failure.
Unit Start-Up
Preparation for start-up
Before starting the unit, use the following procedures
to ensure that the unit is completely and
properly installed and ready for start-up.
The installer must make sure that the following points
are checked before the initial start-up.
1. Inspect all wiring connections. Connections should
be clean and tight. Trace circuits to ensure that wiring
agrees with wiring diagrams provided with the unit.
Information in the title block of the wiring diagram
should match the data that appears on the unit
nameplate.
2. Close the unit power fused disconnect switch and
the manual disconnect switch.
3. Check the unit supply voltage to ensure that the
voltage is within the utilization range.
4. Check the compressor oil level.
5. Check with a phase-meter the direction of rotation
of scroll Trane compressors or check the good
operation of the discharge and suction pressures.
6. As the various motors of the system are started,
check the direction of rotation and make sure that
the driven equipment is operating satisfactorily.
7. Ensure sufficient cooling load available at day of
start-up (minimum of 50% of design load).
Preparation
Before putting the system into operation, perform these
service and check-out procedures :
1. Before making any electrical power connections make
sure that the insulation resistance of all power terminal
to earth is in accordance with the international electrical
codes. Measure the insulation of all electrical motors
using a 500 V DC tester and refer to the manufacturer’s
specifications.
Warning :
No motor should be started if the insulation resistance
is less than 2 mega ohms. Under no circumstances
should any voltage be applied to a motor while it is
under vacuum.
2. Check the unit supply voltage to ensure that the voltage
is within the utilization range.
Caution :
Phase unbalance must not exceed 2% . Supply for all
motors is to be within plus or minus 5% of the voltages
specified on the compressor nameplate.
3. Place all refrigerant circuit valves in operating position.
Installation
