What Is a Suction Hose in an A/C System?

by Steve Hamilton
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Air conditioning (A/C) systems consist of three main components: the compressor, evaporator and condenser. Running between these components are lines carrying refrigerant in various states. The suction line is referred to as a hose mainly in automotive systems where it is usually made of a special rubber rather than metal tubing. The suction hose can also be identified by certain other characteristics.


The suction hose is the cold line. Since it carries refrigerant to the compressor from the evaporator, it is lower in temperature than any line in the A/C system except those inside the evaporator itself.


The suction hose is the low pressure line. When it enters the evaporator, the refrigerant goes from a high pressure liquid to a low pressure vapor. This condition continues until it returns to the suction side of the compressor. Hence the name, suction hose.


The suction hose is the large line. In most A/C systems, especially those in automobiles, the suction hose is considerably larger than the other A/C lines. It is carrying refrigerant vapor and lubricant which must have room to flow with minimal resistance.

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