Neutral Axis

Modulating Thermostat Firmware Glitch

by on Nov.04, 2009, under Uncategorized

Rheem thermostatLast winter I had an old Rheem gas furnace and air conditioner replaced with what amounts to Rheem’s top of the line air-source heat pump system.  Its a dual fuel heat pump with a modulating gas burner and variable speed fan.  To make that part of the system work required a modulating thermostat and the one Rheem sells is made by White Rodgers (Emerson).  Rheem’s model number is RHC-TST411MDMS.  White Rodgers and Emerson refer to it as “Big Blue” under several different variations.  That stat added $300 to the cost and had a stupid programming glitch in it that came to light with the daylight savings time switch last weekend. [Problem resolved, see updates]

[Update 11-5-09:  See comment from White Rodgers offering a replacement.]

[Update 11-6-09:  Commenter Tim Burke of White Rodgers really came through.  Not only has he arranged to send a replacement thermostat, but it will be an upgraded model that will show humidity.  The fact that he was able to discover my post and respond so quickly impressed me, but then I’ve had a soft spot for WR for years.  In college I shared an apartment with a guy who interned for them during the summers, and who’s father worked there.  As a result, I had freebie programmable stats back when they weren’t so common.]

The glitch also happened at the time change in the spring, but I wasn’t sure then if it was my mistake of the stat’s.  The November time change confirmed that it was the stat.  The glitch is that the thermostat computes the DST change date incorrectly if the first of March or November falls on a Sunday.  In both spring and fall of 2009, that’s what happened.  The stat doesn’t seem to recognize that the first can possibly be a Sunday, so it doesn’t count that day and changes the time a week too late.  I can manually adjust the time for the intervening week, but then when the stat thinks its the right time for the change, it will get adjusted and be wrong again.  An email to White Rodgers confirmed the bug.

“This DST issue will only occur in early production models when the March or November DST (Sunday) falls on the 1st, 8th, 15th. This will happen in 2009 and after which the next event will be 2015.  In this scenario, the thermostat will correct itself the Sunday after the DST event.  You can correct it manually now, but next Sunday you will need to correct it again when the thermostat adjust itself late.”

I then asked about getting it swapped out with a new model that doesn’t have the glitch.

“By the time I got you a replacement thermostat and you spent the time swapping them out, the situation would be resolved and won’t be an issue for over 5 years.  If you are still not satisfied, please email back and I will find a way to get you satisfied.”

So it looks like they’re willing to cooperate, but they’re not exactly volunteering.  I called the local Rheem distributor and mentioned the problem to him as well.  He volunteered to check that the thermostats he has on the shelf are glitch-free and will swap mine out with a new stat under warranty.  Its a simple change-out because the thermostat is two pieces, consisting of a base where the wiring is connected, and a display with the brains.  All I will need to do is pull off the old display, and push on the new.

I don’t think I’m being unreasonable in wanting this thermostat replaced.  True, the problem won’t appear again for 5 years, but when it does it means 4 manual adjustments will be necessary that year.  A $300 programmable thermostat shouldn’t create problems like that.  Now hopefully the US Congress won’t decide to adjust DST start and end dates again any time soon.

Download (PDF, 931KB)

9 Comments for this entry

  • Tim Burke

    My name is Tim Burke of White-Rodgers. Of course we back our product and would be happy to send you a no charge replacement with the upgraded software. I am not sure who responded from White-Rodgers originally. Can you give me that name please?

    Can you please see what the model number is on the back of the thermostat so we get the right one for you. Just put it in the OFF system mode and pull off the wall–there should be a White tag on the subbase(where the wires hook up) Send me the model number which is probably something like 1F95-12XX

    Please send directly the model number and your mailing address to:

    and we will have the thermostat sent so you can change it out.

    Best regards,

    Tim Burke

  • Jim V.

    I also own a 1F95-1291, with a date code 0838. When the time adjustment came for DST I thought I was going crazy when it didnt adjust, so I did, and then it did and so on. There is also another firmware glitch in this stat, that being when used in a dual-fuel geo install, and the stat requires the gas furnace to meet the demand for heat, it will switch over to gas just fine, but it will never,ever go back to the heat pump. I have tried to talk to the local rep but to no avail.
    They deny that this is possible, but after seeing this post Im even more confident in what is happening.

    • walter

      I’ll forward your comment to Tim Burke at White-Rodgers. He helped me, so hopefully you’ll hear back from him about your situation.

    • Jim V.

      This is a final update on the White Rodgers thermostat firmware glitch in my last entry. Emerson agreed to replace the stat, although they were not sure what was happening. The new thermostat finally arrived and has been installed and running for 4 or so days. When the time came for a switch to gas for backup heat the new stat performed perfectly. Afterwards it staged the Geo at stage 2, then after a period of time stage 1, The old unit never performed like this. White Rodgers is now in possession of the defective unit, and they are testing to find out what the firmware problem is. At this time they think it may just be a problem with early units. If you are having a similar problem call them, they will work with you and get the problem solved. Jim V.

  • Keith M.

    Walter: I’m confused! You state that you bought a Rheem RHC-TST411MDMS thermostat. The PDF file in your post is for a White Rogers 1F95-1291 which is not the same as the Rheem (its not a modulating thermostat). Then Jim V. says he has the WR 1F95-1291 with the same problem as the Rheem. Do all of the WR/Rheem thermostats have this problem? I had 2 top of the line Rheem modulating heatting/AC systems installed in the first half of 2009 year, both with RHC-TST411MDMS thermostats (manufacture date 08-38 and 08-52). I also have a WR 1F95-1291 for a non-modulating HP system on our 3rd floor (manufacture date 08-19). Maybe Tim can confirm if all of my thermostats have this problem?

    • walter

      Keith, I couldn’t find a PDF of the Rheem model thermostat, so I used that WR 1291 because its the one commenter Jim V mentioned. I didn’t pay close enough attention to see that it wasn’t a modulating stat. So good eye. I have a feeling the DST glitch was probably on all the “Big Blue” style stats.

  • Steve Dune

    Emerson thermostats are the best in both manual and touchscreen, these are efficient and affordable.

  • walter

    Yep, sure enough, the glitch reoccurred in 2015. OK, so a key step in not having this glitch reoccur every few years is to not forget to actually install the replacement thermostat they send.

  • Willan

    White Rodgers thermostat are the best flexible thermostat, easy to use but no color display , don’t have Auto-Schedule

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