Thermo King 098916, Maintenance Manual

Page: 122 / 196

Electrical Maintenance
121
Low Pressure Cutout Switch
A low pressure cutout switch is located on the
compressor suction line. If the suction pressure
becomes too low, the switch opens to stop the
compressor:
• Compressor stops immediately.
• Evaporator and condenser fans continue
normal operation.
• Compressor will restart if the low refrigerant
condition is corrected (switch closes) as long
as power is available. The low pressure switch
resets (closes) when the pressure increases to
28 to 48 kPa, 0.28 to 0.48 bar, 4 to 7 psig.
Low Pressure Cutout Switch:
• Opens: -17 to -37 kPa, -0.17 to -0.37 bar,
5 to 11 in. Hg vacuum.
• Closes: 28 to 48 kPa, 0.28 to 0.48 bar, 4 to
7 psig.
Low Pressure Cutout Switch
Removal
NOTE: Units built before December 2003 do not
have a Schrader valve in fitting and will require
the refrigerant charge to be recovered from the
unit.
On units built before December 2003:
1. Recover the refrigerant charge from the unit.
(see “Recovering Refrigerant from the
System).
2. Disconnect the low pressure cutout switch
wires from the control box.
3. Remove the low pressure cutout switch from
the suction line.
If the unit is equipped with a low pressure sensor,
the LPCO is not used.
On units built after December 2003:
Remove the low pressure cutout switch by
performing the following steps:
1. Disconnect the low pressure cutout switch
wires from the control box.
2. Remove the low pressure cutout switch from
the suction line. The fitting on the suction line
has a shrader valve which will prevent
refrigerant leakage.
1. Low Pressure Cutout Switch
2. High Pressure Cutout Switch
3. Discharge Service Valve
4. Suction Service Valve
Figure 67: Low and High Pressure Cutout Switches
1
2
3
4