Low pressure pressure switches in HVAC systems and high pressure pressure switches are the two basic refrigeration switches in a typical high-grade residential system. It is called high grade because not every refrigeration system of air conditioners and heat pumps has a switch to protect the refrigeration system. Today's focus is on what is a pressure switch used in a refrigeration circuit and how an HVAC pressure switch protects the system from further damage.
The high pressure switch will stop the compressor circuit if the pressure exceeds the pressure switch rating. Ratings will vary depending on the type of refrigerant the air conditioner or heat pump uses with the system.
On some air conditioners or heat pumps, this switch is just reset manually. Because if it trips, there's definitely a problem that needs to be fixed before the system is back up and running.
On Rheem and Ruud heat pumps and air conditioners, the reset button is usually located in red near the control panel. Simply press the switch to reset the switch and the air conditioner should return to normal operation until the pressure exceeds the switch rating.
Things that can cause a high voltage switch to trip include:
1. The condenser fan motor is damaged.
2. The condenser coil is clogged with dirt and debris.
3. The fins on the coil are bent.
4. The refrigeration system is blocked.
If these problems exist, they should be dealt with before resetting the switch. A high pressure switch prevents the system from operating at extremely high pressures. Continuously resetting the switch without considering the problem will lead to a potentially catastrophic failure of the system, resulting in higher repair costs.
The low pressure switch is usually an automatic reset switch that automatically resets when the pressure on the low pressure side of the refrigeration system returns to normal or above the switch setting.
When a refrigeration system is operating below normal pressure, the system can freeze at the evaporator coil at the beginning of the coolant and return to the compressor through the suction line. Freezing of the refrigeration system is bad and leads to clogging of the liquid refrigerant in the compressor, which can lead to compressor failure.
Things that can cause a low voltage switch to trip include:
1. Refrigerant leakage leads to low refrigerant charge.
2. The blower motor in the air handler is faulty.
3. Blocked evaporator coil or blocked airflow.
4. The refrigeration components in the refrigeration system fail.