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  1. #1

    Question Lennox G71MPP -- not set up for variable :(

    I had a G71MPP installed a few months ago, and while the install seemed great, I grabbed the manual tonight because it seemed to me like the unit was kicking on and off in a very much 2-stage way, and not variable. Sure enough, the dip switch to enable variable wasn't flipped (#2), despite the fact the installer told me it was when they installed it.

    Anyway, I flipped it on my own tonight, but now it only runs at 40%. (The diagnostic code that flashes is h40c563.) Is there something else I need to do to get this to truly be "variable"? It is running on the 2-stage Lennox digital (touchscreen) t-stat, so my understanding is this should all be supported "out of the box".

    Right now, for instance, the t-stat is set at 68, and the inside temperature is 62. Yet, it continues to run at 40%. I set the t-stat down to 60 to shut off the furnace, and then put it back to 68. When it fired back up, it flashed h70 a few times on the furnace diagnostic, but then settled on h40 again. Thoughts??

    If not, no worries -- I can get the original installer out here, but if it is just flipping another switch somewhere, just easier to do it myself. Many thanks.

    Mark

  2. #2
    Join Date
    Aug 2008
    Location
    Minneapolis
    Posts
    79
    switch 1 off, 2 on, and 3 off. I don't know about the thermostat set up. I have mine running on a IAQ stat.

  3. #3
    Join Date
    Aug 2008
    Location
    Minneapolis
    Posts
    79
    As long as the thermostat is calling for two stage with a temperature difference like that should be a h70% after 5 minutes goes up to 90% then another 5 minutes 100%. W1 and W2 are wired on control board?

  4. #4
    Confirmed --h switch 1 off, 2 on, 3 off. And yes, both W1 and W2 are wired. I wonder if the installer tried it when he put it in, and it was defective, so they switched it to 2-stage and hoped we wouldn't notice? Regardless, we'll give them a call on Monday and have them come out. Thank you for the help!

    Quote Originally Posted by Therm76 View Post
    As long as the thermostat is calling for two stage with a temperature difference like that should be a h70% after 5 minutes goes up to 90% then another 5 minutes 100%. W1 and W2 are wired on control board?

  5. #5
    Join Date
    Sep 2008
    Location
    NW Pennsylvania
    Posts
    118
    Hope I'm not hijacking the thread but I have a Lennox G71 with a lennox comfortsense 5000 and am wondering how can you check/tell what it's doing at any given moment. I am curious to see how this furnace goes about it's business. I have not taken off the panel and pressed the diagnostic switch but I notice when it runs there are numbers and letters flashing that I'd like to decode.

    It's about 20f out, the thermostat is set to 70f (reading inside at 70f) with fan on, and the furnace is running it's reading h40A444. I just bumped the hit up to 80 then down to 75 then down to 72 and it said h70A715 or so.

    Thanks

  6. #6
    If you've got the manual you should be able to decode these... 'h' means it is on variable capacity heat ('H' would be 2-stage), 40 means it is running at 40% (the lowest output it will run). The number after the A is the CFM -- as I understand it at least -- so 444 cubic feet per minute (CFM), and then when you bumped it up to 80 it pushed the fan speed up to push 715CFM.

    Feel free to correct me if I am wrong... this is gleaned from the manual; I am certainly no expert.

    Quote Originally Posted by Briant73 View Post
    Hope I'm not hijacking the thread but I have a Lennox G71 with a lennox comfortsense 5000 and am wondering how can you check/tell what it's doing at any given moment. I am curious to see how this furnace goes about it's business. I have not taken off the panel and pressed the diagnostic switch but I notice when it runs there are numbers and letters flashing that I'd like to decode.

    It's about 20f out, the thermostat is set to 70f (reading inside at 70f) with fan on, and the furnace is running it's reading h40A444. I just bumped the hit up to 80 then down to 75 then down to 72 and it said h70A715 or so.

    Thanks

  7. #7
    Join Date
    Sep 2008
    Location
    NW Pennsylvania
    Posts
    118
    Quote Originally Posted by warmindenver View Post
    If you've got the manual you should be able to decode these... 'h' means it is on variable capacity heat ('H' would be 2-stage), 40 means it is running at 40% (the lowest output it will run). The number after the A is the CFM -- as I understand it at least -- so 444 cubic feet per minute (CFM), and then when you bumped it up to 80 it pushed the fan speed up to push 715CFM.

    Feel free to correct me if I am wrong... this is gleaned from the manual; I am certainly no expert.
    After I posted I went to read the owners manual, not a lot in there but then I cracked open the installation manual and came across what you just posted. I also read a snippet that seems to imply that when calling for high head it jumpts to 70 when high firing for awhile then adjusts. I tested this and it started at h70A### and then h80 h90 finally it was reading h100A###
    does this sound correct for this furnace?

  8. #8
    Join Date
    Jan 2007
    Location
    Chicago
    Posts
    304
    Quote Originally Posted by warmindenver View Post
    I had a G71MPP installed a few months ago, and while the install seemed great, I grabbed the manual tonight because it seemed to me like the unit was kicking on and off in a very much 2-stage way, and not variable. Sure enough, the dip switch to enable variable wasn't flipped (#2), despite the fact the installer told me it was when they installed it.

    Anyway, I flipped it on my own tonight, but now it only runs at 40%. (The diagnostic code that flashes is h40c563.) Is there something else I need to do to get this to truly be "variable"? It is running on the 2-stage Lennox digital (touchscreen) t-stat, so my understanding is this should all be supported "out of the box".

    Right now, for instance, the t-stat is set at 68, and the inside temperature is 62. Yet, it continues to run at 40%. I set the t-stat down to 60 to shut off the furnace, and then put it back to 68. When it fired back up, it flashed h70 a few times on the furnace diagnostic, but then settled on h40 again. Thoughts??

    If not, no worries -- I can get the original installer out here, but if it is just flipping another switch somewhere, just easier to do it myself. Many thanks.

    Mark
    We are a Lennox dealer, please call the installing company with any issues that you are having. We never suggest a customer open and attempt to adjust any of the dips or anything else on our units. As you are well aware the G71 is the most pricey of the line, and the last thing that you would want is for something to happen and for someone to say that you opened it up, you broke it. Your company should be more than happy to come out and check the operation. I know owners manuals are great and all but ask the service tech to go over the operation with you.

  9. #9
    Join Date
    Sep 2008
    Location
    NW Pennsylvania
    Posts
    118
    I been watching mine now that I know what to watch for and I have seen h40A###, h46A###, h51A###, h70A###, h90A###, h93A### and even h100A####.

    My dips are 1 off 2 on 3 off (in fact two looks glued into place) and w1, w2 are wired. Want to add that I just looked but didn't touch anything.

  10. #10
    For the record, it turned out the t-stat (the Lennox touchscreen) was left in its default 1-stage mode. So, once the installer flipped it over to working as a 2-stage stat, all was good to go... he did have to reset the furnace, since it had been on a learning curve with the 1-stage operation, so he cleared that out. Hoping things work better, now!

  11. #11
    Join Date
    Sep 2008
    Location
    NW Pennsylvania
    Posts
    118
    Simple mistake and simple fix, glad to hear it's working now.

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