Measure temperature drop across inside coil

Air Conditioning and Heat Pumps · Air Conditioning Capacity · printed page 214 (PDF page 215)

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Measure Temperature Drop Across Coil Temperature across Inside Coil of Air Conditioner

Text in the illustration

plenum temperature (typically 55°F to 60°F)
the temperature drop across the evaporator coil should be 15°F to 20°F
(the A/C should be running for at least 15 minutes before performing this test)
return temperature (typically 75°F)
supply plenum
evaporator coil
cold air return
furnace
note: this test goes beyond the Standards

Generated explanation

The illustration shows a furnace with an evaporator coil above it, a supply plenum above the coil, and a cold air return duct connected at the furnace base. Thermometers measure air temperature in the return duct and supply plenum to determine the temperature drop across the indoor coil. Annotations give typical return air temperature as 75°F and supply plenum temperature as 55°F to 60°F, with an expected temperature drop of 15°F to 20°F. The air conditioner should run for at least 15 minutes before this test. A note states that this test goes beyond the Standards.

Components

furnace evaporator coil supply plenum cold air return duct thermometers refrigerant lines

Materials

sheet metal ductwork refrigerant line insulation