Homeowners: Ensure You Are Using the Correct HVAC Piping Materials

Homeowners: Ensure You Are Using the Correct HVAC Piping Materials

HVAC piping is utilized to convey refrigerant between the two coils of a central air conditioner. Though two separate pipes combine to perform that basic function, the specifications of each pipe and the role each plays in the system differ. Refrigerant flowing in a central A/C moves from the evaporator coil to the system compressor, then circulates through the outdoor condenser coil and returns to the evaporator coil.  Two pipes compose this circular flow: the vapor line and the liquid line.

Vapor Line

Also known as the suction line, this larger copper pipe is 5/8 to 3/4 inch in a typical unit sized for home use. It conveys refrigerant in the vaporous state from the A/C evaporator coil in the indoor air handler to the system compressor located in the outdoor condenser unit. To prevent excess heat absorption into the refrigerant as well as inhibit condensation, the suction pipe is always insulated. The suction line typically operates under a pressure of approximately 120 p.s.i.  

Liquid Line

The liquid line conveys refrigerant in a warm liquid state after it has dispersed heat energy at the condenser coil. This pipe is the smaller of the two lines, usually around 3/8-inch in a home HVAC system. The pipe extends from the the outdoor condenser coil back to an expansion valve located at the indoor evaporator coil. The liquid line is not insulated. In a typical system, the liquid line will convey refrigerant under a pressure of about 350 p.s.i.

Certain specifications apply to both the liquid line and the suction line:

  • Both pipes are copper.
  • Both spans are continuous with fittings or connections only at the ends where each connects to a specific component.  
  • Copper HVAC pipes must be supported approximately every 6 feet to prevent deformation or bending.
  • To prevent kinking that could restrict free flow of refrigerant through the pipe, if the pipes must be bent the radius of the bend should not be less than 12 inches.

For more technical details about HVAC piping, contact Paitson Bros., serving Terre Haute and the Wabash Valley since 1922.

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    Jeff Paitson Jeff Paitson is a third generation business owner who continues to run the business with the same values that have been passed down from previous generations since 1922.

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    Ethan Ethan Rayburn is a lifelong resident of Terre Haute and a 2005 graduate of Purdue University.

    An Eagle Scout, Ethan spent four years as a non-profit executive with the Boy Scouts of America before joining Paitson Bros. as a comfort advisor and later General Manager. In that role, Ethan has brought a renewed enthusiasm for customer care, integrity, value, and service to Paitson Bros. Heating & Air Conditioning.

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