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  1. #1
    Join Date
    Sep 2012
    Posts
    373

    new Lennox SL280v not set up for two stage

    I have a quick question regarding our new upstairs furnace that was installed last July.

    Our Lennox SL280v was never wired for "true" 2-stage operation, so the unit runs on low fire for 7 minutes then switches to high. My question is, is it better to have true 2-stage operation where the furnace will only run in high stage when it needs to or is the setup fine the way it currently is? I would like to have true 2-stage operation but I want your opinions on it first. I'm surprised how the installers never ran a W2 wire to the thermostat. The technician who performed our furnace tune-up/inspection several weeks ago said that he could add a wire but said it was optional and it is not impossible to have one added. The thermostat is a Honeywell RTH6450D and it is compatible with multi-stage systems.

  2. #2
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,620
    Up to you. Set up as a two stage via the thermostat gives longer run times and increased comfort. Second stage has a better combustion efficiency so getting there from the timer is not a bad thing.

  3. #3
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,379
    As Marty stated. Having w1 and w2 hooked up at stat will be more comfortable to others.

    Having the furnace fire in only w2 will save you more energy and give you the most heat.

    A lot of people are against me but, I only set furnaces to high fire and tune them with a combustion analyzer. With certain formulas and data I can prove high fire costs less money and gives you more heat.

  4. #4
    Join Date
    Sep 2012
    Posts
    373
    Thanks for the input. I appreciate it. Our upstairs is 1400 sq. ft. and the furnace is 66,000 BTU input on second stage and 43,000 BTU input on first stage. Our furnace is the smallest size the SL280v it comes in. I think that having true two stage control will probably be more ideal because with the furnace running on low the majority of the time, it won't short cycle and will provide more comfort. Also since the upstairs only being 1400 sq. ft., 66,000 BTU sounds a bit too much so that will make the furnace rarely run on second stage.

  5. #5
    Join Date
    Jun 2007
    Location
    Greenwood Indiana (Indianapolis)
    Posts
    420
    You could have a Honeywell IAQ thermostat installed and this thermostat will not require you to have a new thermostat wire pulled. It can do 2 stages of heat with the current wires you have now.
    As iron sharpens iron so one man sharpens another Proverbs 27:17 NIV84

  6. #6
    Join Date
    Sep 2012
    Posts
    373
    Quote Originally Posted by Kevin Weaver View Post
    You could have a Honeywell IAQ thermostat installed and this thermostat will not require you to have a new thermostat wire pulled. It can do 2 stages of heat with the current wires you have now.
    Is it true that it does not need a w2 wire? I thought that all thermostats compatible with 2 stage heat must use a w2 wire to control 2nd stage.

  7. #7
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,350
    Quote Originally Posted by 545GAlady View Post
    Is it true that it does not need a w2 wire? I thought that all thermostats compatible with 2 stage heat must use a w2 wire to control 2nd stage.
    The way the IAQ works is it has 3 wires going to the thermostat from the EIM (interface module mounted near the furnace). The EIM is then wired to the furnace as most thermostats would be. It's a great thermostat and can be set up to control dehumidification in the summer. I agree with the suggestion to look into having one installed.

  8. #8
    Join Date
    Sep 2012
    Posts
    373
    Quote Originally Posted by RyanHughes View Post
    The way the IAQ works is it has 3 wires going to the thermostat from the EIM (interface module mounted near the furnace). The EIM is then wired to the furnace as most thermostats would be. It's a great thermostat and can be set up to control dehumidification in the summer. I agree with the suggestion to look into having one installed.
    Thanks for the info. I just remembered that the thermostat for our downstairs system is a Honeywell visionpro IAQ. Our downstairs system is a dual fuel system and has a single stage furnace (which is a Lennox G40).

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,758
    Quote Originally Posted by 545GAlady View Post
    Is it true that it does not need a w2 wire? I thought that all thermostats compatible with 2 stage heat must use a w2 wire to control 2nd stage.
    The IAQ uses an interface module, known as an EIM. The EIM is mountd at teh furnace, and the furnace wires connect to it, including a W2 wire. Only 3 wires are used to connect to the thermostat on the wall.
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  10. #10
    Join Date
    Dec 2007
    Posts
    4,574
    Quote Originally Posted by 545GAlady View Post
    Is it true that it does not need a w2 wire? I thought that all thermostats compatible with 2 stage heat must use a w2 wire to control 2nd stage.
    the answer to your question is yes, but....

    IF your thermostat has a W2 then it is best to use it in most cases.

    IF your thermostat does not have a W2, most furnaces can control the second stage by the board in it.

    IF you use a more advanced thermostat, like the IAQ or others, the portion the home owner interacts with needs only 2 to 4 wires. HOWEVER, there is a remote module that has all the necessary terminals and it usually gets mounted near the furnace.
    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."
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  11. #11
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,512
    I feel it's just laziness on the part of the install company to sell a 2 stage furnace then not wire it properly, I wll say where I work they do the same crap
    We really need change now

  12. #12
    Join Date
    Dec 2007
    Posts
    4,574
    Quote Originally Posted by catmanacman View Post
    I feel it's just laziness on the part of the install company to sell a 2 stage furnace then not wire it properly, I wll say where I work they do the same crap
    X2

    and the funny thing is the guys where I work say they set it up right, but the manual is still sealed in the package and I know they do not have the info from another source.
    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

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,758
    Have it set up for 2 satage operation by the thermostat. It provides better comfort, by not giving you that sudden cool feeling when it shuts off like single stage furnaces do, or just running in high fire.
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