R32 Superheat and Subcooling UK: How to Set and Verify Correct Charge

Why Superheat and Subcooling Matter for R32 Systems

Setting correct superheat and subcooling is the key indicator of a correctly charged R32 heat pump or air conditioning system. Because R32 must always be charged by weight, verifying these values after charging confirms the system is operating within manufacturer specification and at maximum efficiency.

What Is Superheat?

Superheat is the temperature of the refrigerant vapour above its saturation (boiling) point at the evaporator outlet. It confirms that all liquid has evaporated before reaching the compressor — essential to protect the compressor from liquid slugging.

Typical target superheat for R32 split AC and heat pump systems: 5–10°C at the suction service port (system dependent — always check manufacturer specification).

What Is Subcooling?

Subcooling is the temperature of the liquid refrigerant below its saturation (condensing) point at the condenser outlet. Adequate subcooling ensures liquid refrigerant reaches the expansion device without flash gas, maximising system capacity and efficiency.

Typical target subcooling for R32 systems: 5–10°C at the liquid service port (system dependent).

Measuring R32 Superheat and Subcooling

1. Connect manifold gauge set to system service ports
2. Measure suction pressure and convert to saturation temperature using R32 PT chart
3. Measure actual suction pipe temperature with surface clamp thermometer
4. Superheat = actual temperature minus saturation temperature
5. For subcooling: measure liquid line temperature and liquid line pressure, convert to saturation temperature. Subcooling = saturation temperature minus actual temperature

Sourcing R32 for Charging Work

Our R32 9 kg cylinders are the UK trade standard for heat pump and split AC charging work. Browse our full refrigerant gas range.