Air conditioners and heat pumps are connected to the interior evaporator and condenser by a line set, also known as refrigerant lines. These copper tubes move refrigerant in a cycle through the compressor, condenser, and evaporator providing cool air (or warm air if a heat pump is used in heating mode). While this system can be very efficient, having insulation on the line set can both increase efficiency and help to prolong the life span of the HVAC equipment.
An air conditioner or heat pump line set is usually composed of two pipes which carry the refrigerant between the compressor and the evaporator coils. These lines operate under different pressures and are separated as the low pressure line and high pressure line. These are also called the liquid and suction lines. The suction line is the low pressure line that is larger in diameter and carries the refrigerant from the evaporator coils to the condenser. The smaller liquid line carries the high pressure refrigerant from the compressor to the evaporator coils.
While smaller the high pressure liquid line does not need to be insulated, the larger low pressure suction line requires insulation to protect it from condensation. Without insulation around this line, thermal energy is lost and condensation forms, which can both lower efficiency and cause moisture damage to the unit. If excessive moisture is present, mold and mildew growth can also become an issue. Insulation should be avoided around the high pressure liquid line as this can prevent it from properly releasing heat and lead to lower efficiency.
Line set insulation is typically composed of closed cell foam insulation that is wrapped around the low pressure suction line and held in place with tape or a self sealing adhesive that comes on most line set specific insulation. While polyurethane foam insulation is often used on the interior, rubber based insulation is recommended for exterior installations.
Over time, this insulation can be damaged or become displaced and should be repaired or replaced in order to ensure that the line is protected from condensation. In addition, any holes in the wall or foundation where the line set enters the home should be sealed in order to prevent moisture and pest intrusion.
Keeping your air conditioner or heat pump line set insulation properly maintained is an important part of regular HVAC maintenance and should be checked and repaired as necessary on a regular basis. This can help extend the life and efficiency of your HVAC system and prevent premature repairs.