Weird T-Stat/Zonecontroller issue

Discussion in 'HVAC Heating & Cooling' started by RhoZeta, Nov 1, 2019.

  1. RhoZeta

    RhoZeta New Member

    Joined:
    Nov 1, 2019
    Location:
    Fort Worth
    Having an odd problem that I can not figure out and searches for similar issues turn up nothing so I am posting to the forum in hopes that somebody has seen this before.

    Equipment and setup;
    Trane 5 Ton Heat Pump unit in a 2 story home, using a Honeywell 3 zone controller, (Only uses 2 zones) for upstairs and downstairs. Have two Trane (Honeywell) T-Stats, one upstairs one downstairs with only difference being upstairs T-Stat can also control Emer Heat (Heat strips).

    Problem;
    About 1.5 years ago, came downstairs one morning to the A/C blowing and T-Stat said it was 56F, tried shutting it off at T-Stat and no response. pulled T-Stat off the wall and it shut down. Found the 3 AA batteries leaking acid, upon opening unit found that the acid had damaged the control board. Entirely my fault for not changing the batteries. ( I no longer put batteries in them, system has a power wire, really no need)
    Went to the HD and found a new Honeywell WIFI T-Stat, I think it is a T-5. Installed unit, worked fine except that the A/C would run in A/C or Heat. Did some Trouble Shooting and changed the O wire over to a B system with T-Stat programming changes as well and after that the heat pump would run with heat or A/C called. Spent a frustrating few days trying to figure it out,called the worthless Honeywell help line and they had no clue how to help.
    In TS I can touch the bare wires together and it will call for heat pump and A/C respectively, the upstairs T-Stat works as it should as well.
    Tried another Honeywell T-Stat that is identical to the Trane T-Stat except it is Honeywell branded and same results. In frustration I ordered an identical Trane T-Stat as the damaged one and the problem persist.
    Also in TS I moved the T-Stat and damper from Zone 2 to the unused zone 3, thinking there was possibly an issue with the zone controller and the problem persist.

    In summary;
    I can individually call for A/C and heat using the wires at the thermostat and it works fine so I am assuming wiring from T-Stat to zone controller is good.
    I switched the T-Stat and damper wiring from zone 2 to the unused zone 3 and problem is same.
    The system runs as it should from T-Stat upstairs, set it to heat, heat pump comes on, set it to cool and A/C comes on.
    Zone controller is not indicating any faults and it displays properly with each call, red LED lit up for heat, yellow LED lit up for A/C with condensing unit responding accordingly.

    T-Stats used;
    Honeywell T-5 Lyric WIFI, Performed setup per instructions including equipment selection (1 C 1 HP)

    Honeywell RTHD8500, identical unit to the Trane that was in use before problem.

    Trane TCONT8000, IS the identical part number as the original unit.

    I am game for thoughts and suggestions, thank you.
     
  2. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    How many wires to each thermostat? Any pictures? I'm having a hard time trying to read into what your problem is? Its possible the two thermostat do not have a common ground.
     
    Last edited: Nov 5, 2019
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  4. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    I think I found the issue, the AC runs in AC mode or Heat mode? No Heat, correct? Check the O wire and the programming of the thermostat. For AC you want power on the O lead, for heat pump no power. A valve operates outside at the compressor. The thermostat must know the type of heat and single stage or two stage.
     
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