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Line filter question..............................(Starch)

There are suction filters and suction filter-driers. I use suction filter-driers to clean up a burnout. After it's clean I replace it with a suction FILTER. Less pressure drop and they are designed to remain in the system. If you install a replacable core shell this is quick and simple. I always replace the liquid filter-drier. bob


  • John Starcher_4
    John Starcher_4 Member Posts: 794
    I was told today................

    .....by my favorite supply house dude, that a suction line filter is only necessary when you've had a compressor burnout.

    I'm replacing a condenser and coil for a client, and reusing the existing lineset due to lack of access. (It's a three unit condominium, and we can't get to the entire lineset to replace)

    The client has had no problems with the existing equipment, she is just concerned with its age, and is being proactive. I was always under the impression that a suction line filter should be installed with any condenser changeout, and in the event of a compressor burnout you also install a liquid line filter. I was told the liquid line filter should be placed at the evaporator in this scenario.

    My wholesale guy is insisting that the suction line filter is not to be used, but the liquid line filter is a must. He also says that the liquid line filter can be installed at the condenser.

    Can you please clarify the proper filter method and placement?


  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Driers Driers Everywhere!


    let's address the liquid line filter drier first. The liquid line filter is intended to perform a number of functions including capturing moisture and acid from the system as well as capturing particulates thay may be circulating in the system. Notice that I did not mention that the filter drier REMOVES acid and moisture from the sytem. There are no moisture or acid vents that, like air vents on hydronic systems, facilitate the removal of acid or moisture from the system.

    Since the filter drier is intended to help prevent the metering device from malfunctioning as a result of trapped or stuck particulates, the drier should ideally be close to the meterng device. Typically, however, installation crews install the liquid line filter drier at the condensing unit for ease of installation. This, however, is not the best place for it.

    I personally like to replace the liquid line filter drier whenever the system is opened to the atmosphere for any length of time. The device is n ot costly and I would hate to have to come back on a job because the filter drier is clogged. In addition, I also like to oversize the filter drier. Larger driers clog slower and can capture more system junk.

    As far as suction line driers go, I personally lke to install them, not only after a compressor replacement, but on initial installation as well. One function of the suction line drier is to help trap particulates from reaching the compressor. The suction line drier can't do this if it isn't there. So, in my humble opinion, I am all for installing suction line and liquid line driers on all new installations and replacing BOTH driers after a compressor replacement or after the system has been opened to the atmosphere.

    Sucion line drier close to the inlet of the compressor.
    Liquid line drier close to the inlet of the metering device.
  • Glenn Harrison_2
    Glenn Harrison_2 Member Posts: 845
    Hey Starch

    Long time no talk.

    I was always taught that you should ALWAYS use a liguid line filter drier any time you open up the system, and it should be placed right before the metering device.

    Suction filter driers are only meant for system cleanup after a burnout, and are not meant to be permanatly installed. That's not to say that I haven't seen suction line driers left in for years without a problem, but I have also seen my fair share of restricted suction line driers that were left in too long.

    In the case of this particular install, I would definatly just use the LL drier at the evap. Just make sure your purge the lines with nitrogen or CO2 and pull a deep vacuum. If your really concerned about the lines, get an RX-11 flush kit from your supplier, and run it through the lines to really get them clean.

    And now I see the professor types faster than I do, and has a different opinion on suction line driers than what I was taught.

    Here's a link to some great reading material on filter driers from Sporlan. Page 26 has a very good procedure on it. I see they seem to go along with the professor on the suction drier. Now I just have to remember where I was taught no to leave them in. Oh well, learn something new every day.

  • don_144
    don_144 Member Posts: 27
    And remember

    to cutout the drier.The torch is made to put the new one in only.
  • John Starcher_4
    John Starcher_4 Member Posts: 794
    Thanks, guys......

    ....I appreciate the feedback. And, you all just confirmed what I thought!!

    Glenn, thanks for the link - I'm sending a copy to my wholesaler.

  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    A Word about Suction Line Driers

    As with any other device that is brazed into the sytem and has Schrader ports, please remember to remove the valve stems before brazing.

    Also, quite often the schrader pin on suction line driers are shipped either loose or competely removed from the drier. Be sure to put them in the drier before charging the system! I can remember in my younger years that I forgot to put the pin in the drier and then removed the cap to connect my low side gauge.

    Funny though, you only make those mistakes once.
This discussion has been closed.