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Mitsubishi troubleshooting

Heat pump communication

If the Mitsubishi heat pump is not successfully communicating with Passiv Smart Thermostat then check the following:

  • Check the RS485 cable connections within the Mitsubishi indoor unit and confirm continuity back to the previous device
  • Confirm the screening drain wire is interconnected and earthed at a single point e.g. Programmer earth
  • Ensure a single twisted pair (e.g. white core + black core) is used for A (white core) & B (black core). Do NOT double up cores or use cores from different twisted pairs for A & B connections
  • Check the Mitsubishi settings have been successfully applied

If the Passiv Smart Thermostat is replacing an existing Mitsubishi wireless remote controller, then it will be necessary to change DIP switch SW-18 to OFF to avoid a J1 error on the main Mitsubishi controller.

Relay controlled Mitsubishi

In the event the MelcoBEMS RS485 Modbus module is not available, it is possible to control heating only via IN1 in TBI.1 7 & 8 on the FTC6 or FTC7 (main) and DIP switch SW2-1 should be set ON. These connections are then wired to the Passiv Programmer "Voltfree 1" COM and NO connections using an appropriately rated cable.

Within the Mitsubishi main controller menu, 1-zone temperature control select control option D.