Lennox G71MPP - How can I tell if it's running in variable mode?
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  1. #1
    Join Date
    Oct 2009
    Posts
    6

    Confused Lennox G71MPP - How can I tell if it's running in variable mode?

    I just had a new furnace installed (Lennox G71MPP) which is supposed to have variable stages, up to 60. However, after looking at the diagnostic code on the furnace, I've noticed only the following three codes appear at different various times:

    "H2A945"
    "H1A622"
    "A410"

    I know the "H" stands for heat and the last three digits represent the CFM. However, my concern is that the unit is only running in stage 1 or stage 2.

    After reading a very helpful older thread:
    http://hvac-talk.com/vbb/showthread....ghlight=G71MPP

    ...I would think that I should see 2 digits between the H and A, representing the variable %.

    For example, "H63A720" would mean the heat is running at 63%, right?

    Since I am only seeing 1 digit after the H (either a "1" or "2"), is my furnace only running in two stage mode?

    Also, the previous thread discussed checking the dip switches. I'm not sure how to find my dip switches. Any pointers?

    If anyone else has a Lennox G71MPP that can verify how to determine if the furnace is running in true variable mode instead of two-stage mode, I'd greatly appreciate any tips.

    Thanks so much!

    My setup
    Furnace = Lennox G71MPP
    AC = Lennox XC13
    Humidifier = Aprilaire 600a
    Thermostat = Honeywell VisionPro 8000 (3H / 2C)

  2. #2
    Join Date
    Oct 2009
    Posts
    6
    Well, I figured out the answer to my own question. The vendor who installed my furnace did not set it up properly.

    If your G71MPP furnace flashes a code starting with capital "H", then it is not configured properly and it is running in two-stage mode.

    If your furnace flashes a code starting with lowercase "h", then it is properly running in variable mode.

    Similar to the other thread, the #2 dip switch had to be flipped up (or on) to put it in variable mode. The dip switch is very small and on the left side of the board behind the bottom furnace panel.

    It's unfortunate that these furnace vendors are not setting up the G71MPPs properly, especially since we are paying several hundred dollars more for the variable speed functionality.

    Finally, so far I've only noticed levels of:
    "h40A###"
    "h70A###"
    "h80A###"
    "h100A###"

    So, I haven't been impressed with the furnace itself and the variability of the stages. It may have been better to just stick with the two-stage model for less money.

    I hope this thread helps others.

  3. #3
    Join Date
    Feb 2009
    Location
    Fox Lake IL
    Posts
    436
    Just give it time you will come to love your furnace. When you are stay warm and you get you first gas bill. if the furnace is keeping you warm stop watching your furnace it will just drive you crazzy.

  4. #4
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    Quote Originally Posted by elgoosh View Post
    So, I haven't been impressed with the furnace itself and the variability of the stages. It may have been better to just stick with the two-stage model for less money..
    What are you not impressed about on this furnace?

  5. #5
    Join Date
    Oct 2009
    Posts
    6
    Probably my biggest frustration is with the installers, instead of the furnace itself. After doing some more internet research, it seems to be a common problem was this furnace. HVAC companies are not setting them up properly, and it's a simple matter of understanding the diagnostic code and flipping a switch. My guess is that the two-stage mode is the default setting and a lot of people who bought this furnace have it running in two-stage mode and probably don't realize it.

    The other reason I wasn't too impressed is due to the lack of variability from what I've seen so far. I've checked the code maybe 3-4 times per day out of curiosity as I pass the furnace room. I've only seen levels of 40%, 70%, 80% and 100%. It's supposed to have 60 stages, not just four.

    True, the furnace is keeping us warm. However, I think we would have been just as warm with the next model level down, G61, which is a true two-stage furnace for over $400 less cost.

  6. #6
    Join Date
    Feb 2009
    Location
    Fox Lake IL
    Posts
    436
    Yes there was alot of furnace put in and not set up right. The company I work for did the same thing after we figered it out thay run like a champ.I have the same furnace in my home.What thermostat do you have? the way the stat is set up may have something to do with it. you should have a IAQ or the stat from lennox and thay need to be set right. Make sure it is and it will work the best. It take time for the furnace to learn the heat curve.

  7. #7
    Join Date
    Oct 2009
    Posts
    6
    Thanks for the info. They gave me a VisionPro 8000 (3 stage heat / 2 cool). I haven't even checked the installation settings for the thermostat. Is it possible something is setup wrong in the thermostat that is limiting it to only 4 stages? (40%, 70%, 80% and 100%)?

  8. #8
    Join Date
    Feb 2009
    Location
    Fox Lake IL
    Posts
    436
    Have not used that stat on this furnace.Is this set up with a heat pump? the stat should be set for 2 stage with w1 and w2 wired in. and the recover turned off. when i had class with lennox dont think thay wonted that stat with that furnace. try and see if thay will put the lennox stat in.

  9. #9
    Join Date
    Dec 2007
    Posts
    4,661
    G71 also "learns" from the prior run.
    It will not start off in the lowest position if it had to ramp all the way up to satisfy temp setting. It will start out at a higher position and then ramp up from there.
    If you have the manual, which it sounds as if you do, read through it and pay close attention to its variable stage features.
    Yes, the stat being set up incorrectly can affect the furnace.
    I would also suggest that the thermostat be switched out for the Lennox Comfort Sense 5000, re badged and additional/different programming, version of the Vision Pro 8000.

  10. #10
    Join Date
    Oct 2009
    Location
    Vancouver, BC
    Posts
    12
    My new Lennox XP15/G71MPP is also flashing "H1A622" at various times. I will contact my furnace installer to have this investigated. I also spent about 500 more for the variable speed option in BC. Was there anything that needed to be changed on your Honeywell VisionPro 8000?

    Elgoosh, do you leave your temperature settings at a consistent temperature throughout the day/night.

    Thank You very much for sharing this.

    Lennox G71MPP
    Lennox Heatpump XP15
    Honeywell VisionPro TH8320U 3H/2C

  11. #11
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    Quote Originally Posted by pacnw View Post
    I would also suggest that the thermostat be switched out for the Lennox Comfort Sense 5000, re badged and additional/different programming, version of the Vision Pro 8000.
    What is the person going to gain with the Lennnox's t-stat vs the Honeywell? Does this stat up and down all the stages like the Rheem's Mod stat, rather than the Lennox locking in the high stage untill heat is no longer called for?

  12. #12
    Join Date
    Oct 2009
    Posts
    6
    Thanks everyone. I have recently seen my furnace run in some other stages such as 59%, 78%, etc. I didn't do anything to change my thermostat. As pacnw pointed out, the furnace probably needed a few weeks to "learn" my environment and adjust as needed.

    Westlaker, it sounds like you had the same problem as me. Apparently, there is a setting on the T-stat that you have to make sure is configured properly, but I would first check the furnace. If you take the bottom pannel off, make sure dip switch #2 is UP or ON (I think it's the only white switch where the others are a burnt orange). It's small, and on the left side of the board, and you may need a very small screw driver to push it up. Once it shows lowercase "h", it's setup properly and you're good to go.

    I hope this helps.

  13. #13
    Join Date
    Nov 2009
    Location
    Vancouver
    Posts
    1
    Yes, I have a similar question. My Lennox G71MPP is running in 2 stage based on the H code that is coming up. I looked at the dip switches and can see #2 is in the off position. Silly question but I see the 3 rows of dip switches all have a clear protective covering over them so not sure how to actually access the #2 dip switch to turn it on so I can get the furnace to go in variable stage instead of 2 stage? Does this protective cover come off? Also, anything I need to do to the thermostat to get it to run in variable stage?
    My setup is:
    XP19 Heat Pump
    G71MPP Gas Furnace
    Comfortsense 7000 thermostat

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