New Thermostat Overheating House

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HeatingHelp
HeatingHelp Posts: 737
in Thermostats and Controls
This discussion was created from comments split from: How to test which wire is R and W in a 2 wire only thermostat?.

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  • glassman
    glassman Posts: 16
    edited October 15

    I was trying to figure out how to post a question here, and for the life of me, I couldn't figure it out.

    I am posting it here in the hope that the mods can redirect it for me, or someone can tell me how to do it.

    I don't imagine it matters in this instance, but the thermostat is connected to a gas fired steam boiler.

    I am installing a Lux TX9100Uc battery powered thermostat to replace a Lux 9000.

    It is only 2 wires. I would have sworn on my children that I had the wires right, but this is now happening: I had the thermostat programmed to activate the boiler at 65 degrees. It was in the mid 70's, so no activity, as expected. Then, when it got to about 70, the heat turned on! I was surprised, but not as surprised as I was when it got up to 79 degrees. It wouldn't shut off!

    I shut the circuit breaker off and shut down the electrical to the boiler for good measure, and that eventually stopped it from running the boiler.

    There is a pre installed 'jumper wire' (?) from the 'RC to the 'RH' terminals. The 2 wires that ran the old thermostat are black and white. I connected the white one into the 'RH" terminal which already had one part of the jumper wire, and the black wire to the 'W1' terminal. This was the configuration under which that scenario occurred.

    My question is, what happens if I reverse those wires, putting the black to the 'RH' terminal and the white to the 'W1' terminal? Again, I would have sworn I had them right, but that is the only thing I can think of to try at this point. Is it a 'no harm, no foul' situation, or am I going to need a whole new whatever if I try this? As they say on Game of Thrones, 'winter is coming!' Help! Thanks so much.

  • Jamie Hall
    Jamie Hall Posts: 27,883

    Fancy! That is, I believe, a two stage heat/cool programmable? Overkill for your boiler… however, all is not lost. I suspect that there may be a programming problem in setting up the thermostat. Go through the manual very very carefully and verify which output is the first stage heat and make sure your black wire is connected to that. Then go through the whole programming and make sure that all the options are correct.

    Should do the trick.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    glassman
  • 109A_5
    109A_5 Posts: 4,584

    I'd turn circuit breaker back on if the boiler comes back on and is uncontrollable I would disconnect one of the wires (or both) from the thermostat. That should shut the boiler down. If does not, it is a thermostat wiring to the boiler issue or a boiler issue.

    Since you only have two wires to the thermostat it really makes little difference if the Black and the White are reversed.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • HVACNUT
    HVACNUT Posts: 7,730

    The thermostat is battery powered so it doesn't matter which wire is on Rh or W1. As long as they each have one. Rc is for cooling so you dont need the jumper but its not hurting anything.

    I would go through the programming again and confirm all times and temperatures are correct. Then I would bypass the program by pressing the "Hold" button to see if it comes on and goes off the way its supposed to. If it does, it's programming. If it still overrides, check for the wires touching maybe behind the thermostat.

  • EdTheHeaterMan
    EdTheHeaterMan Posts: 12,816
    edited 2:00AM

    After taking a close look at the manual for the LUX 9100 thermostat, I believe there is one instruction that you need to follow. It is even posted on the wiring diagram for a Heat Only system.

    image.png

    I have made all the other terminals faded out. The heater is a one stage system and the RC is not necessary. If you connect the wires this way the system should work just fine. If it does not, then there are too many adjustable settings to go thru, so I might use the HW RST Hardware Reset feature to start over from scratch. If that does not work you can try the SW RST Software Reset to remove all user entered variables and put them back to the factory default.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • 109A_5
    109A_5 Posts: 4,584

    I'd first figure out if the thermostat is the actual issue. If it is not the thermostat actually causing the problem fooling with it will never resolve the issue.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • HeatingHelp.com
    HeatingHelp.com Posts: 282
    edited 2:51PM

    @glassman, I've created a new discussion for you here to prevent confusion within that older thread. Here are some tips for using the forum: https://heatinghelp.com/forum-user-manual/

    Forum Moderator

  • glassman
    glassman Posts: 16

    To everyone: Thank you so much! I saw my question disappear from where I put it and had no idea where to look for it! Whatever stage is below 'computer illiterate', you can slot me in there!

    Is this the only way to connect with you fine folks, through the 'comment box'?

    I was thinking there would be a reply option for each answer, but again, as Sargent Schultz used to say on Hogan's heroes, 'I know nothing'!

    I will try 'all of the above'.

    ========================================================================

    One answer from 109A_5 does confuse me though. The system was working fine into the spring. The only thing I did to it was to replace the sight glass, which involved switching off the electric, closing the valves at the top and bottom of the sight glass, removing the old and replacing the new glass (it turned out that just the upper bushing was bad, but I broke the glass slightly removing it, so replaced the glass, bushings and washers). Did all that, other than fighting the upper and lower valves on the sight tube with a little PB blaster, that seemed to go well.

    So when I put the new thermostat in, and it apparently did send a signal to the boiler because it did start to run, doesn't that prove that both the thermostat and the boiler are working, just not in sync?

    ================================================================================

    Ed the heaterman, that is the diagram I used, simply those 2 wires. It couldn't be any simpler, right?

    I think the hardware and software resets are a good idea. If I play back the settings by going through them, they seem to be good, but maybe there is something screwing up there that I am missing.

    ===========================================================================

    HVACNUT, when you say 'wires touching behind the thermostat', there are no bare wires beyond the connections to the screws. Are you suggesting that even insulated wires touching might be an issue?

    Also, it is okay to disconnect the thermostat wires while the circuit breaker is live and the boiler is running?

    =================================================================

    Jamie Hall: This is fancy??!!! Who knew, certainly not me. I didn't think you could buy anything fancy for 40 bucks anymore!

    Basically, I had a Lux9000. It served me well for 15 years plus, until it didn't. So, I figured I would go to the Lux people and tell them what I had and ask for a more or less current replacement. That's how I came to pick that, on their suggestion. Easy peasy is the name of the game for me, so this has turned into a bit of a nightmare by my standards! Thank God for the great people on this website!

    +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

    Well, I think it's time for my nap! When you're pushing 80, pretty much any time is time for a nap😊, so I will try all this great stuff tomorrow. Again, thanks to one and all, you guys are great!

  • HVACNUT
    HVACNUT Posts: 7,730
    edited 9:08PM

    @glassman , no, of course I'm not suggesting insulated wires touching would be an issue. I'm say its possible the insulation stripped somewhere and there might be a short.

    If you remove the wires from the thermostat, or even one wire, the boiler should stop. Power on of course.

  • glassman
    glassman Posts: 16

    Thanks for the clarification. I knew it didn't make any sense, but sometimes what I 'know' is a day late and a dollar short.

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