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2441TH - Random blank screen on one, random mode change HEAT to OFF on other

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    2441TH - Random blank screen on one, random mode change HEAT to OFF on other

    Well here's a zinger I am still working on. I have a house with two outbuildings. The outbuildings are on subs off the main at the house so it is all the same electrical system. Let's call them "House" and "building1" and "building2".

    Two years ago, I installed a 2441TH in both House and building1. They have been working flawlessly ever since. House has both heat and central AC and building1 is just a ceiling-suspended gas garage furnace (electric start, no pilot) with heat only. There is an Insteon Hub in each building and I use the Insteon "House Management" feature to manage each building separately.

    Recently, I finally added a bunch of Insteon equipment to building2 which never had any before. This includes several light switches and dimmers, a garage door sensor and another (third) 2441TH attached to a very old heat-only furnace.

    Since I have done this, I find that the LCD on new 2441TH in building2 randomly goes blank. When this happens, I lose any connection to it from the apps and from Alexa but the furnace keeps running. At the same time, the 2441TH in building1 has suddenly started randomly changing its mode to OFF. This is very disturbing as the outside temps are now well below freezing and that building has plumbing and we are leaving for Florida soon. The 2441TH in House is apparently unaffected.


    As regards the mode change, I read in another thread that a furnace's electric-piezo starter can send a voltage surge to the tstat that can cause a mode change to OFF. But suddenly? After two years of flawless operation? Just when I added another thermostat in another building?

    Here is what I have done so far:

    For the random blank screen issue:

    1) Installed several 1626-10 Plug-In Powerline Noise Filters as a precaution, mostly on appliances with motors and compressors (furnaces, dehumidifiers, refrigerators, etc.) and one or two power bars. No change.

    2) Replaced the (40 year old) wiring in the furnace from the transformer to the gas valve (furnace in building2) with a harness that includes a 24VAC surge protector, fuse and ground. Used contact cleaner on spade connectors, screws plus dialectric grease. Turned the power back on the the thermostat came right up. Bingo! But wait, no, seconds later it went blank again. The valve is getting power, and the stat is connected to the same lugs. Why would the thermostat go blank? (This is a simple three-wire system, R to R, C to C and W to W. No green. Furnace has its own fan control sensor. No AC or other stages.)

    3) Removed both thermostats from their corresponding building/hub.

    4) Factory reset (at least I think I did, see below) and I pressed the "secret" reset button.

    For the random mode change issue:

    1) Same as 1 above.

    2) Added same 24VAC surge suppressor.

    3) Same as above

    4) Same as above.

    Result? So far, I have not seen either symptom again over several hours. I will keep monitoring and report.

    Factory reset:

    Manuals states:

    Factory Reset
    1) Press and hold Insteon Thermostat’s Set button until it beeps.
    Insteon Thermostat will beep.
    Insteon Thermostat Set LED will blink green.
    2) Press and hold Insteon Thermostat’s Set button again until it beeps.
    Insteon Thermostat will beep.
    Insteon Thermostat Set LED will blink red.
    3) Double-tap Set button.
    4) Press and hold Set button again for about 10 seconds.
    Insteon Thermostat will emit a long beep and its display will blink all segments.
    5) When blinking/buzzing stops, release Set button and wait 10 seconds.
    Insteon Thermostat will perform a series of self tests, then return to normal operations.
    Insteon Thermostat display will return to normal.

    The problem is, nothing after step 3 does anything. Holding for 10 seconds does NOT produce a long beep. Nor does the display "blink all segments" whatever that means. Rather, the LED just turns off and you find that it is starting over at step 1. There is no blinking/buzzing or anything like that. Both tstats were the same. So did I perform a reset? Dunno. But pressing the "secret" reset button inside on the PCB did maybe?

    Screwey thing today. At our church, with 9 Insteon thermostats, the power did some weird stuff. 3-phase power, one leg died, one leg became 25vac, and one leg stayed at 120vac like normal. Then, an hour or so later the power came back on normal. I assume it was the 25vac leg that screwed with the...

    Most likely it is coincidence. The likelihood of adding something in 1 building affecting another is extremely low. It's akin to me saying my neighbor bought a new TV which is why mine broke....hmmm, On the other hand, I might need to use that excuse .Lol

    If I were in your shoes, I would replace them with something different. It's one thing to keep trying something when you're in the area. It's another to be out of town worrying about them going bad.. some things are worth paying for to ensure reliability.


      Update. Minutes later, checked tstat in building2 and LCD screen was blank again. Checked it using Windows 10 Insteon for Hub app and it was online. Went back and looked at tstat and the screen was back again.

      Next day. This morning all thermostats online and working. The good news is that the tstat that was changing modes has not been found once in the OFF state since adding the surge protector. This problem could now be solved. The blank screen issue, not sure yet.

      Next day, 8:30 AM. 2441TH in building2 was dead again. Furnace was blasting heat but screen was blank and unreachable from apps. Opened it, pressed the "secret" reset button, closed it and it came back on.

      Same morning... 2441TH in building1 was on OFF. Mode had changed during the night to OFF. If the outside temps had been colder I am afraid I would be facing a burst pipe situation this morning. NO GOOD. These tstats will have to be removed/replaced. With little time left to spend debugging this issue, I will have to drain the pipes in building1 before leaving for Florida and run a space heater near the main as a precaution. $#@%^&!
      Last edited by Chuckster; 12-14-2019, 07:27 AM.


        Just found this post.

        This blank screen issue must be due to loss of voltage. (No 24VAC tester here) Will try external power supply.


          Final synopsis of blank screen issue: This was indeed caused by the limit switch. This is an old Sears gas-fired 867 circa 1968 with a Honeywell fan/limit switch. It has 110 VAC on both sides of the device and when the furnace hits it's limit temp, the switch shuts off power to the transformer.

          The problem is likely caused by the fact that this is a 7500 BTU furnace in a small outbuilding with limited return (incoming) and heat ducts (outgoing) air supply. It has probably been shutting off via the limit for years but only now that I installed a smart thermostat was it noticed.

          It could also be a partially faulty limit switch but the switch is working and rotating and doing its job. Before changing out the switch, I need to get more air in and out of the furnace so that it does not overheat! Meanwhile, I am adding a secondary 24VAC power source and relay to keep the tstat powered up.


            Originally posted by Chuckster View Post
            Final synopsis of blank screen issue:
            My advice: Ditch the Insteon thermostats. They are absolute garbage. Poorly designed, poorly executed and poorly built. Give yourself peace of mind and put in standard thermostats.