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  1. #1
    Join Date
    Mar 2004
    Posts
    171

    Rheem Modulating Stat Reading too Low?

    New construction on 2 story completed in September 2006. Rheem Mod downstairs, and a rheem 2 stage in the attic to service the upstairs. Had no problems with heat this winter, except for the Mod Stat going bad on us and having to get a replacement.

    We keep the temperature set at about 77 F upstairs on the Honeywell thermostat, and that keeps things comfortable. Downstairs, we have the stat set at 71 F and it still feels warm downstairs. We set an indoor/outdoor thermostat on top of the mod stat, and it reads 76 F. The downstairs has more windows and two sliding patio doors, but even on days when the doors are not opening and closing a lot. It feels warmer downstairs than upstairs. If we set the thermostat lower, it gets cool enough, so I don't think there is a problem with a leak or anything else wrong with the setup.

    Can the thermometer on the mod stat be recalibrated? Any other thoughts on why it feels warmer downstairs?

  2. #2
    Join Date
    Oct 2006
    Location
    So. NH
    Posts
    745
    I have the same thing and had the same problem, you can go into the menu and adjust it. It has been brought up by some this may cause it not to modulate properly and I do have some questions about that.

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,907
    I wouldn't think calibrating the actual reading would affect operation at all. No complaints from the guy we did it for recently.

  4. #4
    Join Date
    Jul 2007
    Location
    north east Illinois
    Posts
    11
    Witch stat do you have the old one or the new blue screen?

  5. #5
    Join Date
    Oct 2006
    Location
    So. NH
    Posts
    745
    I have a blue screen, there has been several threads about this but not sure if anyone ever came to a resolution. It does not seem to be a isolated incident.

  6. #6
    Join Date
    Jul 2007
    Location
    north east Illinois
    Posts
    11
    If you have the installation manual, it will tell you how to adjust the temp. on the stat in the instalers configuration

  7. #7
    Join Date
    Oct 2006
    Location
    So. NH
    Posts
    745
    That's what I said and did, Thanks for the input though.

  8. #8
    Join Date
    Aug 2002
    Location
    manitowoc wisconsin
    Posts
    4,943
    Seal the hole in the wall that the wires come through.
    Take your time & do it right!

  9. #9
    Join Date
    Oct 2006
    Location
    So. NH
    Posts
    745
    Did that too, interior wall, put ins. from behind, sealed holes top and bottom, used armaflex to seal where wires entered t-stat. No change. This of course is my situation and not the original posters, but alot of coincidence.

  10. #10
    Join Date
    Jul 2005
    Posts
    10
    We have exactly the same set up with the Rheem 2-stage upstairs and Rheem Mod down. Both are connected to identical 2.5 ton Rheem heat pumps. Also have the new W-R/Rheem blue screen thermostats.

    In cooling mode, I have noticed that the Mod system brings the furnace blower fan on for several minutes before the condenser kicks on outside. At the end of the cycle, the fan stays on after the outside unit shuts down. This does not occur on the upstairs unit. Seems to me this is not good for humidity control.

    The installer has said this must be related to the Mod units (this was his first installation) but he has not been out to check.

    Is this a furnace, heat pump or thermostat issue?

  11. #11
    Join Date
    Mar 2004
    Posts
    171
    Original poster here. Our T-stat was on an interior wall, and I put several different thermometers on top of the new blue screen stat, and all thermometers read 4-5 degrees above the mod stat. Unfortunately, you can only adjust the mod stat +/- 4 degrees, but + 4 degrees did the trick and seems to be more in sync with the upstairs. I do notice that the downstairs seems to be a bit more humid, particularly during this nasty NJ heatwave, but that may be due to us opening and closing the outside doors, which is not an issue upstairs.

    The installer's config menu is not for the technically challenged. Fortunately, I'm used to progammable logic controllers for industrial furnaces during my engineering days, but the menu did take a little figuring out to get to the right place to change the temperature setting.

  12. #12
    Join Date
    Nov 2003
    Posts
    91
    One of these days someone will have the answer to the touchscreen thermostate issue concerning the problem with the temp offset function (when thermostat offset is adj to anything other than zero the furnace only runs on high). Come on Rheem step up to the plate with some answers. Other that small problem, the furnace is wonderful.

  13. #13
    Join Date
    Oct 2006
    Location
    So. NH
    Posts
    745

    new info

    I just made a new discovery on this problem. With heating season arriving I started to wonder again what was going on with this. I reset the temp display to 0 from 2 because it always read 2 degrees low, but wouldn’t modulate, only run on high. Furnace now modulates. I thought maybe the constant backlight maybe throwing it off so I turned it off to check. To my surprise the next time I looked it was in perfect agreement with 2 other thermometers in the room for the first time ever. I though I had it until I went to show my wife how the light would only come on if you touched the screen. It didn’t, and then I remembered I had shut off power to the furnace while I changed the filter but didn’t turn it back on. I turned it back on and in 10 minutes back to reading 2 deg low. Turned power back off, 10 minutes all better again. Back on 2 deg low again. I can’t explain why but power from the furnace is definitely causing the misreading. On battery power it’s perfect. With this new info hopefully someone can help figure this out.

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