Tennessee Cool 2 Lockout

Discussion in 'Maintenance and Troubleshooting' started by gorilla33, Jun 1, 2022.

  1. gorilla33

    gorilla33 Member

    Bosch 6 Ton Unit. I have a 3 zone system utilizing a Honeywell HZ 432 Control Panel. What I have noticed in recent days is that I am getting a Mode 2 cooling lockout(flashing light on zoning board) with a DAT in the 45-49F range. Is this normal?

    This happens in the evening when the unit attempts to drop my temps. Daytime setpoint is 75F(which causes the unit to run very little) and at 9pm it drops to 70F for sleeping purposes.

    I believe that the is a protective feature to keep the coil from freezing, but not sure that I should be having the issue. Of note, if I press the “mode” button on the HZ432 the unit will cut off and when the unit comes back on it runs with Mode 2 cooling in operation.
  2. SShaw

    SShaw Active Member Forum Leader

    Sounds like the leaving air temp is too low, triggering the low temperature lockout. Increasing airflow will raise the DAT. With three zones, you likely have airflow issues when all zones are not open.

    You could take steps to increase the airflow (e.g. replace air filter, use less restrictive filter, cool other zones at night, adjust zone dampers to allow some leakage into closed zones, ensure all registers are open, etc.)

    A quick google search seems to indicate the default temperature limit for the Honeywell zoning boards is 45F but the HZ432 has an adjustable lockout temp from 30F to 60F. So, you could also lower the limit a bit to avoid the lockout. You run the risk of freezing the coil if you go too low, so more airflow would be better solution.
  3. gorilla33

    gorilla33 Member

    I am cooling all zones at this time and all filters are completely new. Do you have any idea how to change the lockout temp?
  4. SShaw

    SShaw Active Member Forum Leader

    No. I'd suggest you do an Internet search for the installation manuals and look up the procedure.

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