Refrigerant Superheat UK: What It Is and How to Measure It Correctly

What Is Refrigerant Superheat?

Superheat is the temperature of refrigerant vapour above its saturation (boiling) point at a given pressure. It confirms that all liquid refrigerant has evaporated before reaching the compressor suction — critical for protecting the compressor from liquid slugging damage.

Why Superheat Measurement Matters

Low superheat risks liquid returning to the compressor. High superheat indicates undercharge, restricted refrigerant flow or a faulty expansion device, and reduces system efficiency and capacity. Correct superheat means the system is running at its designed operating point.

How to Measure Superheat

1. Connect manifold gauges to the suction (low-pressure) service port
2. Read the suction pressure and convert to saturation temperature using a PT chart for the refrigerant in use (R32, R410A, R407C etc.)
3. Measure the actual suction pipe temperature with a clamped surface thermometer, as close to the service port as possible
4. Superheat = Actual pipe temperature minus saturation temperature at measured suction pressure

Typical Superheat Targets

• Split AC / heat pump (R32 or R410A): 5–10°C at service port
• Commercial refrigeration (R404A): 5–8°C at suction service port
• Scroll compressors: Often specify minimum 10°C superheat — check manufacturer data

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