Condensing temperature
Also known as: condensation temperature, saturated discharge temperature
Short definitionThe temperature at which the refrigerant turns from vapour to liquid in the condenser. It is 10–15 K above ambient; the lower it is kept, the less electricity the compressor uses.
To reject its heat, the vapour in the condenser has to be warmer than the outside air. In an air-cooled condenser the difference is 10–15 K; at 35 °C ambient, condensing rises to around 45–50 °C. Discharge pressure is the saturation pressure of this temperature. Each 1 K rise increases compressor consumption by 2–3% and lowers capacity. If it climbs too far, the high-pressure switch stops the system.
In a project this value is set by the size of the condenser and where it stands. A condenser that is undersized, or placed in an airless corner or in full sun, raises condensing in summer. A dirty coil, a faulty fan, air in the system and overcharge give the same result. In winter, letting condensing fall with fan speed control and an electronic valve cuts annual consumption by 10–20%. With a mechanical valve, condensing is not taken below 25–30 °C.