THERMOSTAT
A cross ambient thermostat is used to maintain the desired comfort level. The thermostat reacts only to a change in temperature at the bulb location. Important to the successful operation of the unit is the position of the sensing bulb in relation to the evaporator.
SENSING
BULB LOCATION
RANGE: Thermostat
(Part No.
60° F ( ± 2° ) to 90° F( ± 4° )
WARNING
ELECTRIC SHOCK HAZARD
Disconnect power to the unit before servicing. Failure to follow this warning could result in serious injury or death.
TESTING THE THERMOSTAT
Remove the wires from the thermostat. Turn the thermostat to its coldest position. Check to see if there is continuity between the two terminals. Turn the thermostat to its warmest position. Check continuity to see if the thermostat contacts open.
Note: The temperature must be within the range listed to check the thermostat. Refer to the troubleshooting section in this manual for additional information on thermostat testing.
LOW AMBIENT BYPASS VALVE
WARNING
HIGH PRESSURE HAZARD
Sealed Refrigeration System contains refrigerant and oil under high pressure.
Proper safety procedures must be followed, and proper protective clothing must be worn when working with refrigerants.
Failure to follow these procedures could result in serious injury or death.
The HazardGard unit is designed to operate at low outside ambient temperatures. This is accomplished by the use of a bypass valve installed in the refrigeration circuit. The valve is connected between the discharge line at the compressor and the suction process tube. The valve responds to suction pressure which, when reduced in the system, causes the valve to open and bypass hot gas from the high pressure side to the low pressure side of the system. The hot gas entering the compressor mixes with the cool gas returned through the suction line, thus increasing the suction pressure. The valve is preset to open when the suction pressure reaches 50 psig. This pressure setting cannot be altered. The system can be operated at outdoor temperatures as low as 45°F before the evaporator coil will begin to accumulate frost.
To determine if the valve operates, block the return air to the evaporator coil. Turn on the unit and touch the tube at the bypass valve outlet which connects to the suction process tube. When the low side pressure reaches approximately 50 psig, the valve will begin to open and the tube will get hot. This method will determine if the valve is responding to the suction pressure change.
LOW AMBIENT
BYPASS VALVE
12
