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  1. #1
    Join Date
    Aug 2012
    Posts
    6

    Condensate drainage done the RIGHT way

    Contractor just installed a Lennox SLP98V furnace, with an AC-coil directly on top of it. They used 3/4" PVC tubing to drain the AC pan across the top of the furance, then straight down. BUT, they TIED IN the furnace condensate drain directly into the AC drain, with the common pipe running to a condensate pump (see picture below). The Lennox Installation manual says both condensate drain lines MUST drain independently (i.e. one from the AC and a separate from the furnace). Contractor says, no my install is fine and "newer" version of the manual (which I can't find online) confirm this setup is ok.
    Thoughts? Not sure why you can't tie this together.

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  2. #2
    Join Date
    Apr 2003
    Location
    Maple Grove, MN
    Posts
    1,338
    My guess would be that they are worried about the trap on the evaporator section (which appears to be missing from your install) drying out during heating mode, and then there would be a minute possibility of flue gas getting sucked into the evaporator section.

    If you are going to leave it like that, at least put a trap on the upper portion of the piping before it ties into the heating drain.

  3. #3
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,944
    There needs to be a break between the AC condensate and the furnace condensate. Positive pressure from the upflow coil will put pressure on the furnace trap and cause drainage issues on the furnace side. I do pipe them together, but install vents in between so one does not influence the other. Not a firm believer that traps on the ac side will solve problems because without ac condensate flow they will dry out over the winter.

    Its hard to see in this picture but both drains end up in the same line, but they are both independently vented after the respective traps.

    Where is your secondary drain off the AC?

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  4. #4
    Join Date
    Dec 2007
    Posts
    4,718
    manual on DaveNet, page 26, figure 41, now shows them tied together.

    referring to your manual attachment, instead of the 90° down from the furnace trap it is now a tee into the a/c drain line. this is an option, but they still do show your attachment method.

    both lines have their own trap and vent.
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
    from an excerpt by Paul Jacob in Sun City, AZ

  5. #5
    Join Date
    Dec 2007
    Posts
    4,718
    Quote Originally Posted by beshvac View Post
    There needs to be a break between the AC condensate and the furnace condensate. Positive pressure from the upflow coil will put pressure on the furnace trap and cause drainage issues on the furnace side. I do pipe them together, but install vents in between so one does not influence the other. Not a firm believer that traps on the ac side will solve problems because without ac condensate flow they will dry out over the winter.

    Its hard to see in this picture but both drains end up in the same line, but they are both independently vented after the respective traps.

    Where is your secondary drain off the AC?

    Name:  DSCN0946.jpg
Views: 501
Size:  36.9 KB
    that photo is really hard to make out the drain lines, traps and vents.

    I cannot see a trap in the a/c line, it appears to run down into the tee that is coming out of the furnace, then into a "J" trap and then behind the large pvc venting is a vent in the 3/4" line- is that correct?
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
    from an excerpt by Paul Jacob in Sun City, AZ

  6. #6
    Join Date
    Aug 2012
    Posts
    6
    Quote Originally Posted by pacnw View Post
    manual on DaveNet, page 26, figure 41, now shows them tied together.

    referring to your manual attachment, instead of the 90° down from the furnace trap it is now a tee into the a/c drain line. this is an option, but they still do show your attachment method.

    both lines have their own trap and vent.

    I can't log into DaveNet (private site).. PACNW: can you show us the picture for the new tie-in directions (AC ties into furnace condensate safely)?

  7. #7
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,944
    Quote Originally Posted by pacnw View Post
    that photo is really hard to make out the drain lines, traps and vents.

    I cannot see a trap in the a/c line, it appears to run down into the tee that is coming out of the furnace, then into a "J" trap and then behind the large pvc venting is a vent in the 3/4" line- is that correct?
    The T you can see is the furnace vent after the trap. the trap on the AC is behind this. The single drain is above the plumbing drain. It's not a good pic.

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