Where is the LLP located in a heat pump system?

The low-pressure lockout switch (LLP) is designed to monitor the system pressure and ensure safe operation of the heat pump. Its essential function is to prevent the compressor from running under low-pressure conditions, which can be damaging and inefficient.

The correct location of the LLP is on the bi-flow liquid line between the two coils. In this position, the switch effectively senses the refrigerant pressure in the system, allowing it to perform its safety function by shutting down the compressor when low pressure is detected. This placement is critical because it enables the LLP to monitor the conditions that affect the entire heat pump operation, including both heating and cooling modes.

The other locations mentioned do not serve the same purpose. For instance, being at the outdoor coil or the indoor coil near the heat exchanger would limit its ability to monitor overall system pressure effectively. Similarly, placement within the compressor unit would not allow for proper pressure monitoring across the entire system, as the compressor is only one component and does not reflect the pressures in the liquid line. Thus, positioning the LLP on the bi-flow liquid line is the most effective way to ensure the heat pump system operates safely and efficiently.