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  1. #1
    Join Date
    Aug 2008
    Location
    San Clemente, CA
    Posts
    1,229

    Single condensate drain line for a Lennox C33 cooling coil and SLP98 FAU

    Condensate water cannot overflow or back up into the fau heat exchanger with this set up. Equipment is set in fau closet with a raised platform for return air. Home has very nice hardwood flooring all around this interior fau closet. With this mechanical switch I don't anticipate water damage from this installation. Without these safety switches a condensate back up on a call for cooling would fill the heat exchanger, overflow the fau vent/trap assembly and make a mess.

    John



    3/4" Cross tee allows for the installation of a safety switch to break the "Red".


    Photo taken from the back of closet looking out at drain assembly and me.


    Drawing of this drain set up.

  2. #2
    Join Date
    Jan 2011
    Posts
    614
    Add on txv's? Lennox still in the stone age?

  3. #3
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,051
    So you write these manuals for lennox jkopp?

    I have to admit they are by far the best instructions ive seen.

  4. #4
    Join Date
    Aug 2008
    Location
    San Clemente, CA
    Posts
    1,229
    Thanks SBKold, I have a passion for doing illustrations that are correct. So many of them are not correct. Some of my work has made it into Lennox install instructions. The coil condensate drain line drawing, equipment hold down method and equipment elevation extenders fixed and adjustable for the XC series units using 2" ABS fittings to name a few. I also have several HVAC related patents.

    We purposely install coils with external TXV valves because we have had to replace a few. Much easier when they are external.

    John

  5. #5
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,051
    noticed you posted on jimmyeds picture about combining puts positive pressure on fau but I'm curious what happens once water evaporates from the trap?

    From the pictures of actual install I can see how your vent placement provides the solution.

    However just going by diagram it does not stress the importance of installing the vent never perpendicular to air flow thru trap.

    I also cant see the actual lower vent configuration in the install pics.

  6. #6
    Join Date
    Aug 2008
    Location
    San Clemente, CA
    Posts
    1,229
    One of the issues with our install is the factory FAU trap clean-out is going to be very hard to get to being this is a closet install. Then I am now reviewing Lennox's latest and greatest install instructions and they redesigned the trap clean-out. Maybe to make servicing the thing easier? They and I have both routed the drain line in front of this new horizontal clean-out. It would take installing a 90 fitting to offset the drain line over from in front of the clean-out depending on how much room one has. Looks like I need to rework my drawing.


  7. #7
    Join Date
    Nov 2009
    Location
    Kansas City
    Posts
    124
    I myself always run evap coil dain and furnace drain completely separate. Lennox changes their condensate trap every month I think

  8. #8
    Join Date
    Aug 2013
    Posts
    16

    Lennox SLP98 condensate trap

    Quote Originally Posted by Bsmith816 View Post
    I myself always run evap coil dain and furnace drain completely separate. Lennox changes their condensate trap every month I think
    Am considering replacing a 14 year old Keeprite with the SLP98, updraft, side return. Have had an XC14 for the last four years, without trouble. Would be using an iComfort.
    The owner/dealer (who only sells Lennox) who came to give a quote on the installation said he would combine the AC condensate drain with the furnace condensate drain, and run them both into the basement floor drain.

    When I asked about a trap, he said he didn't use them - because they always clogged. Without a trap there would be no clogs. He has been in the business about 30 years, has done HVAC installs for a nation-wide TV renovation show, and out of the four people who came to quote, he is the one I would prefer to go with, based on his discussion of my needs. His quote was not the least expensive.

    But I am puzzled over this trap question. There is now no trap on the AC coil, nor is there a secondary drain, and have had no problems. Is it OK to go with no trap on the furnace drain, too?

  9. #9
    Join Date
    Dec 2012
    Location
    Lowell,MA
    Posts
    51
    you can go with no trap on the ac because it is an updraft blower and will always be positive pressure on the drain but no do not go with out a trap on furnace especially if tying in drains together. if it is a high efficiency furnace should be trapped inside but i would not tie into same line due to positive pressure from blower pushing back into furnace trap run separate line should be ok

  10. #10
    Join Date
    Aug 2013
    Posts
    16
    Thanks! That is very helpful.

  11. #11
    Join Date
    Dec 2007
    Posts
    4,718
    Look in the install manual and it will show a photo of just how to do it.

    Be careful, some of Lennox's equipment specifically CANNOT be tied together!!!
    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

  12. #12
    Join Date
    Jun 2012
    Location
    Northeast
    Posts
    296
    Quote Originally Posted by George36 View Post
    Am considering replacing a 14 year old Keeprite with the SLP98, updraft, side return. Have had an XC14 for the last four years, without trouble. Would be using an iComfort.
    The owner/dealer (who only sells Lennox) who came to give a quote on the installation said he would combine the AC condensate drain with the furnace condensate drain, and run them both into the basement floor drain.

    When I asked about a trap, he said he didn't use them - because they always clogged. Without a trap there would be no clogs. He has been in the business about 30 years, has done HVAC installs for a nation-wide TV renovation show, and out of the four people who came to quote, he is the one I would prefer to go with, based on his discussion of my needs. His quote was not the least expensive.

    But I am puzzled over this trap question. There is now no trap on the AC coil, nor is there a secondary drain, and have had no problems. Is it OK to go with no trap on the furnace drain, too?
    When adding a cooling coil after a furnace the coil is on the positive side of the fan. If you do not install a trap with a large enough column of water you will be blowing cold and hot air down the drain line. Not sure what percentage it would be but I would prefer to see it not do that.

  13. #13
    Join Date
    Oct 2011
    Location
    Bothell, WA(Seattle)
    Posts
    245
    Cleaner/primer on the PVC? Tell me it's clear and exists.

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