Unit Description
29
Unit Protection Devices
Coolant Level Switch:
The coolant level switch
closes if the coolant level drops below an
acceptable level. If it stays closed for a specified
time, the microprocessor records alarm code 37.
Engine Coolant Temperature Sensor:
The
microprocessor uses the engine coolant
temperature sensor to monitor the engine coolant
temperature. If the engine coolant temperature
rises above an acceptable level, the
microprocessor records alarm code 41 and
possibly 18. The the microprocessor might also
shut the unit down.
Fuses:
Various fuses are located on the base
controller to protect circuits and components. See
“Base Controller Fuses” on page 83 and “Battery
Fusing” on page 87 for more information.
Smart FETs:
Smart FETs in the base controller
protect circuits and components.
High Pressure Cutout Switch:
The high pressure
cutout switch is located on the compressor
discharge manifold. If the compressor discharge
pressure becomes excessive, the switch opens the
circuit to the run relay to stop the unit. The
microprocessor will record Alarm Code 10.
High Pressure Relief Valve:
This valve is designed
to relieve excessive pressure in the refrigeration
system. It is located on the receiver tank. The
valve is a spring-loaded piston that lifts off its seat
when refrigerant pressure exceeds 500 psig (3447
kPa). The valve will reseat when the pressure
drops to 400 psig (2758 kPa). The valve could
possibly leak refrigerant after it has relieved
excess pressure. Tapping the valve lightly may
help the valve reseat and seal properly. The valve
is non-repairable and requires no adjustment. If
the valve fails to reseat properly, recover the
refrigerant charge and replace the valve.
Low Oil Level Switch:
The low oil level switch
closes if the oil drops below an acceptable level. If
it stays closed for a specified time, the
microprocessor shuts the unit down and records
alarm code 66.
Low Oil Pressure Switch:
The low oil pressure
switch closes if the oil pressure drops below an
acceptable level. If it stays closed for a specified
time, the microprocessor shuts the unit down and
records alarm code 19.
Preheat Buzzer:
The preheat buzzer sounds when
the controller energizes the preheat relay. This
warns anyone near the unit that the controller is
about to start the engine.
Overload Relay—Automatic Reset (SmartPower
Units):
An overload relay protects the standby
electric motor. The overload relay opens the
circuit to the electric motor if the motor overloads
for any reason (e.g., low line voltage or improper
power supply) while the unit is on electric standby
operation. The microprocessor will record Alarm
Code 90.
