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New heat pump with 5/16" liquid line?

Does anyone know of manufacturer that has ratings for their heat pump to be used with a 5/16" liquid line? We have a replacement job, that has an existing 25' silv flos'ed liquid line that we would like to re use. I know most manufacturers now are calling for 3/8", But if possible we would like to re use this line and save the customer the extra charge in having it replaced. Thanks to all. '


  • Steve MinnichSteve Minnich Member Posts: 2,474
    About 25 years ago, I had a compressor fail within the warranty time frame. I was denied the warranty because I used a 7/8" suction line on 4 ton system that should have had a an 1 1/8" suction line because of its extended length. That was a hard lesson to learn. I never give them an opportunity to deny, anymore.
    PHC News Columnist
    Minnich Hydronic Consulting & Design
  • JUGHNEJUGHNE Member Posts: 6,154
    Was this 5/16 on an old R-22 system?
    Ruud/Rheem did the 5/16 years ago.

    A new 410A HP?
  • zepfanzepfan Member Posts: 273
    Thanks for the response. It is a Trane 1987 2 ton, r22 air handler, and we would be installing an 410a hp and air handler
  • unclejohnunclejohn Member Posts: 1,420
    Should be ok up to 3 tons. Add as much 3/8th as you can at the unit. I have never had a warranty job denied.
  • JUGHNEJUGHNE Member Posts: 6,154
    Is the remaining oil from the R-22 system a concern?
    Or how do you deal with it?
    Or is it as much of the issue that was thought when 410A became popular?
  • John Mills_5John Mills_5 Member Posts: 930
    Rheem is fine with it in long lengths up to 3 on, above better be pretty short.

    Otherwise I'd check with tech support on the brand you want to use. I called 1 brand once and was told absolutely nothing less than 3/8". Dead comps usually don't go back so yes, warranty won't be denied but it will cost someone!

    Old lines blow out with nitro and unless you had a burnout, should be OK. Of course if easy to change I'd much rather see shiny new copper. POE oil is a GOOD cleaner removing any crud built up on the inside of the old lines.
  • JUGHNEJUGHNE Member Posts: 6,154
    On a walk in cooler I had both TXV plugged screens twice after 134A and new oil.
    So for a heat pump with possibly TXV inside and out, also reversing valve, where is the best place for the bi-flow filter drier.....would one for each end be a consideration?
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 6,101
    5/16 will be fine for 2 tons. Blast it with nitrogen first
  • G Averill_2G Averill_2 Member Posts: 44
    Our refrigeration and air conditioning staffs recommend a product by Nu Calgon, item number Rx-11-flush when changing refrigerants. Take a look on their website.
  • pecmsgpecmsg Member Posts: 954
    Flushes cause more damage and are not advised. just blow out the line set. No issues with a mixture of POE & MO.
    Remember the POE oil is a cleaning agent, We recommend a suction filter in use for several days to trap any and all crap that will come back to the compressor. Remove it after a few days.
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