High Pressure Switch Protection

The outdoor unit is equipped with high pressure switch. If the control senses the opening of a high pressure switch (open 600+/-5 psig, close 470+/-10 psig @77°F), it will respond as follows:

 

1. Display the appropriate fault code (see Fig. 31).

 

2. After a 6 minute delay, if there is a call for cooling or heating and HPS is reset, the PEV opens for 150 seconds to equalize system pressures. Compressor and fan will then ramp to the next lower stage of operation until demand is satisfied. Staging down and Resetting to the highest stage will end after 2 hours of accumulated operation without further HPS trips.

 

3. A system malfunction will occur after repeated HPS faults and the stage has reached the lowest level. This could take five consecutive HPS trips if the first occurred in stage 5 demand, or 1 HPS trip if in stage 1 demand.

 

4. In the event of a high-pressure switch trip or high-pressure lockout,check the refrigerant charge, outdoor fan operation, and outdoor coil (in cooling) for airflow restrictions, or indoor airflow in heating.

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Low Pressure Protection

The outdoor unit is equipped with suction pressure transducer. If suction

pressure drops below 15 psi at any time, or below 33 psi for 5 minutes,

the compressor and fan will stop running and an error code will be displayed on user interface.

1. If there is still a demand for unit operation after the 15 minute delay and pressure has increased to >43psi (cooling) and >35psi (heating)

, system will resume operation.

2. If there are three (3) consecutive trips because of suction pressure

dropping below 15 psi, the low pressure switch will lock out

operation for 4 hours. Trip counter will be reset after 15 minutes of

successful operation.

3. When a change in demanded stage occurs, suction pressure is

checked at each stage in between current and demanded stage. This

is to prevent ramping of compressor speed too quickly and creating

a low pressure situation. As long as suction pressure is >=45psi,

the compressor is able to ramp to next stage. If suction pressure is

lower than required, additional wait time at current stage will occur.

4. In the event of a low-pressure trip or low-pressure lockout, check

the refrigerant charge and indoor airflow (cooling) and outdoor fan

operation and outdoor coil in heating