Thermo King T-1080S, Maintenance Manual

Page: 129 / 191

Refrigeration Service Procedures
128
compressor is probably faulty if it cannot raise
the discharge pressure by 100 psig (689 kPa)
or to 375 psig (2586 kPa).
NOTE: It may be necessary to remove the
upper grille insert to cover the condenser.
6. Remove the cover from the condenser and run
the unit in low speed cool.
7. Pump down the low side by front seating the
receiver tank outlet valve and allowing the
low side to pump down to a 5 in. Hg vacuum
(-17 kPa).
NOTE: If the low side will not pump down
into a vacuum, the hot gas solenoid, the
liquid injection solenoid, the purge valve, or
the receiver tank pressure check valve may
be stuck open. See the individual component
tests for more information.
8. Front seat the suction service valve to isolate
the low side while it is still in a vacuum.
9. Turn the unit Off.
10. Watch the low pressure gauge attached to the
suction access port. The low side pressure
should not rise.
• If the low side pressure rises to 0 psig
(0 kPa) and stops, there is probably a leak
to the atmosphere. Check the low side for
leaks.
• If the low side pressure rises above 0 psig
(0 kPa) and continues to rise (until it
eventually equalizes with the high side
pressure), there is probably a leak from the
high side to the low side through one (or
more) of the following components: hot
gas solenoid, liquid injection solenoid,
purge valve, or receiver tank pressure
check valve. Check the temperatures of
the refrigeration lines on each side of these
components by hand. There is often a
temperature difference between the two
sides of a leaking component. See the
individual component tests for more
information.
11. Back seat the suction service valve and then
the receiver tank outlet valve. Perform a
“Refrigerant Gauge Removal” procedure.
Low Side Pump Down
NOTE: Operate the unit in cool for 2 to 5
minutes before performing the low side pump
down.
1. Attach a gauge manifold to the suction service
valve and the discharge service port. Attach
another low pressure gauge to the suction
access port located in the suction line near the
accumulator inlet. Low loss fittings must be
used on the hoses connected to the discharge
service port and the suction access port.
2. Operate the unit in low speed cool.
3. Front seat the receiver tank outlet valve and
allow the low side to pump down to 0 to 5 in.
Hg vacuum (0 to -17 kPa).
NOTE: To check certain components, front seat
the suction service valve to isolate the low side
while it is still in a vacuum. See “Refrigeration
System Checks” and the individual component
tests for more information.
4. Turn the unit Off.
5. Prepare to perform service on the low side by
raising the low side pressure through the
gauge manifold to 1 to 2 psig (7 to 14 kPa).
6. Front seat the suction service valve to isolate
the low side. The discharge check valve in the
compressor is an imperfect seal and will not
keep the discharge pressure from leaking back
through the compressor. Use the suction
access port located near the accumulator inlet
to access the low side for leak testing and
evacuation.
7. Back seat the suction service valve and then
the receiver tank outlet valve. Perform a
“Refrigerant Gauge Removal” procedure.
CAUTION: Do not pull scroll compressor
into a vacuum below 10 in. Hg vacuum
(-34 kPa) to perform routine maintenance
procedures.
CAUTION: Do not run scroll compressor
in a vacuum for more than 1 minute.