How to Size Refrigeration System Piping

August 29, 2001
/ Print / Reprints /
ShareMore
/ Text Size+
Among a service tech’s many responsibilities is to pipe together refrigeration system components. When piping a system together, a technician must decide which pipe size to use — it’s not always as simple as it may appear.

A general knowledge of piping practices is required to make an intelligent choice. Normally, each of the system components has a stub connection of a specific pipe size. Using the stub connection size as a guide to determine which pipe size to use is generally not a good practice.

Equipment manufacturers design their stub connections for the average or most common pipe size used. The actual pipe size needed may be larger or smaller. Several factors help determine which actual pipe size to use:

  • Type of refrigerant used;
  • The system’s capacity; and
  • The total length of pipe between the two components.


  • The Suction Line

    Of the major sections of pipe, the suction line is the most critical to size properly. Generally, the suction line is sized for a minimum pressure drop through the line and a minimum velocity in order to ensure good oil return to the compressor. Incorrectly sizing the suction line can lead to oil return problems or a reduction in the system’s capacity.

    If the pipe chosen is too large, the velocity of the refrigerant flow will be reduced. Since the refrigerant is in a gaseous state in the suction line, it does not mix well with the refrigerant oil. The velocity of the gaseous refrigerant helps to push the oil along the suction line. If the velocity is too low, the oil will collect in the suction line in the evaporator. This will lead to a shortage of oil at the compressor that can cause damage.

    If the suction line is too small, oil return will not be a problem. However, there may be an excessive pressure drop through the suction line. This will reduce the system’s capacity. Deciding which pipe size to use for the suction line is generally a compromise between ensuring good oil return and maintaining a minimum pressure drop through the line.



    Discharge and Liquid Lines

    It is also important to correctly size the discharge and liquid lines. However, in the discharge line the refrigerant is traveling at a higher velocity, the oil is pushed along, and the pipe size is not as critical. In the liquid line, since the refrigerant is in its liquid form, it tends to mix well with the refrigerant and is carried along easily.

    Most manufacturers will include recommended pipe sizes with their installation and service literature. Technicians need to refer to this material when piping in any component. If the original installation and service literature is not available, there are universal tables and charts available to aid in choosing the right pipe size.

    Always refer to the appropriate sizing chart rather than simply basing the pipe size on the component’s stub connection. This will always ensure the right size is chosen for the job and that the system will function properly in its design refrigeration capacity.

    Marchese is owner of Arctic-Air Refrigeration, Pittsburgh, PA.

    Publication date: 09/03/2001

    Did you enjoy this article? Click here to subscribe to The NEWS Magazine

    You must login or register in order to post a comment.

    pipe size and length

    winston reginio
    May 3, 2008
    sir, would you give me some information about the size and the legth of pipe depending the capacity use in domestic refrigeration. i used as my referance to my study. thank you

    pipe size and length

    winston reginio
    May 3, 2008
    sir, would you give me some information about the size and the legth of pipe depending the capacity use in domestic refrigeration. i used as my referance to my study. thank you

    15 ton single circuit R 22 unit.

    inder
    September 3, 2008
    but its only 4 feet long.and 4 lbows

    refrigeration

    dinos
    September 10, 2008
    where can i find a chart for sizeing coper lines

    Suction velocity

    mike
    January 8, 2009
    On a 5 ton system, what is the velocity of R-22 inside of a 1 1/8 copper line.

    walk in freezer

    tony
    May 2, 2010
    do you know the math's for calculatin a walking frezzer,,,,9 x 7 x 7...-10 degres .....85 degres out side,,,

    request

    sayou
    May 20, 2010
    sir, would you give me some information about the size and the legth of pipe depending the capacity use in domestic and commercial refrigeration plans. i used as my referance to my study. thank you

    A/C PIPE SIZES

    sam awolaiye
    January 22, 2011
    Sir would you give me some information on the sizes and legth of A/C pipes

    Multimedia

    Videos

    Image Galleries

    2014 MCAA Annual Convention

    Scenes from the 2014 MCAA Annual Convention in Scottsdale, Ariz.

    Podcasts

    NEWSmakers: Julian Scadden

    Training is an ongoing process. Julian will discuss how you can generate maximum return on time and energy invested training by following a three part process. Listen to this podcast to get expert tips on training, tracking and follow up. 

    More Podcasts

    THE MAGAZINE

    ACHRNEWS

    NEWS 04-14-14 cover

    2014 April 14

    Check out the weekly edition of The NEWS today!

    Table Of Contents Subscribe

    SERVICE CALLS POLL

    Which statement on service calls best applies to your business?
    View Results Poll Archive

    HVACR INDUSTRY STORE

    plumbing-hvac.gif
    2014 National Plumbing & HVAC Estimator

    Every plumbing and HVAC estimator can use the cost estimates in this practical manual!

    More Products

    Clear Seas Research

     

    Clear Seas ResearchWith access to over one million professionals and more than 60 industry-specific publications, Clear Seas Research offers relevant insights from those who know your industry best. Let us customize a market research solution that exceeds your marketing goals.

    DON'T MISS A THING

    Magazine image
     
    Register today for complete access to ACHRNews.com. Get full access to the latest features, Extra Edition, and more.

    STAY CONNECTED

    facebook icontwitter iconyoutube iconLinkedIn i con