Unit Protection Devices

High Pressure Cutout Switch (HPCO): This normally closed switch monitors the discharge pressure at the compressor. It opens on high discharge pressure to shut the unit down to prevent damage.

Electronic Throttling Valve (ETV): (T-1200R only)T-1300X only This component is an electromechanical control device used to limit the suction pressure to the compressor. The valve is controlled by the microprocessor controller.

Engine Oil Pressure Switch/Sensor:

• Units built before September 30, 2020 -

  The engine oil pressure switch/sensor is located on the filter head above the bypass oil filter. Engine oil pressure should rise immediately on starting. If engine oil pressure drops below 11 ± 3psig (76 ± 20kPa), the switch/sensor signals the microprocessor to stop the engine.

• Units built September 30, 2020 and after -

  The engine oil pressure switch/sensor is located on the engine block near the oil filter. Engine oil pressure should rise immediately on starting. If engine oil pressure drops below 11 ± 3psig (76 ± 20kPa), the switch/sensor signals the microprocessor to stop the engine.

Suction Pressure Regulator (SPR, T-590 Only):This component is a mechanical control device used to limit the suction pressure to the compressor. The valve controls suction pressure based on the actual system pressure.

Engine Oil Pressure Switch/Sensor: The engine oil pressure switch/sensor is located on the filter head above the bypass oil filter. Engine oil pressure should rise immediately on starting. If engine oil pressure drops below 10 ± 2 psig (69 ± 14 kPa), the switch/sensor signals the microprocessor to stop the engine.

Preheat Buzzer: The preheat buzzer sounds when the CYCLE-SENTRY system energizes the glow plugs. This should warn anyone near the unit that the CYCLE-SENTRY system is about to start the diesel engine.

Coolant Temperature Sensor: This sensor provides an engine coolant temperature input to the microprocessor. If the engine coolant temperature is too high, the controller stops the unit and records an alarm.

Electric Motor Overload Relay (Model 50)(Model 50): The overload relay protects the electric standby motor. The overload relay opens the circuit from the contactor to the electric motor if the motor overloads for any reason and an alarm will occur. The relay resets when the alarm code is cleared.

Fuses: Sizes and functions are described in the Specifications chapter of this manual.

Electric Heat Overlaod (Optional): Units equipped with the electric heat option are protected by an overload circuit to protect the electrical system of the unit.