Thermostatic Expansion Valve

Is it necessary?

A thermostatic expansion valve in a swimming pool heat pump is designed to calibrate the amount of refrigerant the heat pump needs to operate efficiently at varying outdoor temperatures. The alternative to a thermostatic valve is to use a calibrated flow rater.

The flow rater delivers an equal amount of refrigerant to the evaporator. This system is calibrated in a temperature controlled laboratory where the conditions are simulated to be at their coldest.

Most pool heat pump manufacturer's use a thermostatic expansion valve because it is so much easier to install and needs no calibration. Maybe they do not have access to a lab to calibrate a flow rater.

But, there can only be advantages to having a flow rater instead of a thermostatic valve. The flow rater is more efficient at low temperatures when heating will be in demand. That is also when a heat pump is the least efficient. So, a flow rater that is calibrated at these temperatures will be more efficient than the thermostatic valve. Also, the flow rater has no moving parts. This means that the thermostatic valve has a higher risk of failure than the flow rater. The repair cost of thermostatic valves will also be higher.

The Elite, Hybrid, and Sunriser models all have calibrated flow raters. They are designed to operate at low temperatures for highest efficiency and reliability.