General Assist Technical Reference

Backup Operation - V Series

Cooling and heating backup operation when a compressor is defective
Service procedure for multi-outdoor-unit V Series systems
Purpose: Backup operation allows the system to continue operating after isolating an outdoor unit with a defective compressor. The defective compressor can then be replaced without stopping the complete system.
Important limitation: Backup operation may not be able to continue if the total capacity of indoor units in operation is less than 60,000 BTU.
Qualified service personnel only: Stop operation and isolate power to all outdoor units before changing DIP switch settings, disconnecting transmission wiring, or closing refrigerant/oil valves.

1. Backup operation overview

Backup operation is used when one compressor in a multi-outdoor-unit system is defective. The defective outdoor unit is isolated and the remaining outdoor units are reconfigured so the system can continue operating.

ScenarioSystem action
Master unit compressor defectiveSlave unit 1 is reassigned as the master and the system is reconfigured as two outdoor units.
Slave unit 1 compressor defectiveThe defective slave is removed from operation and slave unit 2 is reassigned as slave unit 1.
Example used in the service information: Three outdoor units are connected before backup operation is configured.

2. Cooling backup - master compressor defective

  1. Stop the operation and turn off the power of all outdoor units.
  2. Fully close the 3-way valves (Liquid, Gas and Oil) of the master unit.
  3. Set slave unit 1 as the master unitand structure the system as two outdoor units:
    • Change DIP SW 3-3 / 3-4 (Outdoor unit address setup) of slave unit 1 from [OFF / ON] to [OFF / OFF].
    • Change DIP SW 4-1 / 4-2 (Connected number of slave units) of slave unit 1 from [ON / OFF] to [OFF / ON].
  4. Set slave unit 2 as slave unit 1:
    • Change DIP SW 3-3 / 3-4 (Outdoor unit address setting) of slave unit 2 from [ON / OFF] to [OFF / ON].
  5. Unplug the transmission connector from the master unit's PCB, or do not turn on power to the master unit at Step 6.
  6. Turn on the power and wait for 30 seconds or more.
  7. Check the LEDs:
    • Slave unit 1: Display of Inverter Communication error.
    • Slave unit 2: No error display.
  8. Backup operation is ready.

3. Cooling backup - slave unit 1 compressor defective

  1. Stop the operation and turn off the power of all outdoor units.
  2. Fully close the 3-way valves (Liquid, Gas and Oil) of slave unit 1.
  3. Set up the system as two outdoor units:
    • Change DIP SW 4-1 / 4-2 (Connected number of slave units) of the master unit from [ON / OFF] to [OFF / ON].
  4. Set slave unit 2 as slave unit 1:
    • Change DIP SW 3-3 / 3-4 (Outdoor unit address setting) of slave unit 2 from [ON / OFF] to [OFF / ON].
  5. Unplug the transmission connector from slave unit 1's PCB, or do not turn on power to slave unit 1 at Step 6.
  6. Turn on the power and wait for 30 seconds or more.
  7. Check the LEDs:
    • Master unit: If the error is less than level 1, the system is ready for backup operation.
    • Slave unit 2: No error display.
  8. Backup operation is ready.

4. Heating backup - master compressor defective

  1. Stop the operation and turn off the power of all outdoor units.
  2. Fully close the 3-way valves (Liquid, Gas and Oil) of the master unit.
  3. Set slave unit 1 as the master unitand structure the system as two outdoor units:
    • Change DIP SW 3-3 / 3-4 (Outdoor unit address setup) of slave unit 1 from [OFF / ON] to [OFF / OFF].
    • Change DIP SW 4-1 / 4-2 (Connected number of slave units) of slave unit 1 from [ON / OFF] to [OFF / ON].
    • Change DIP SW 4-3 (Solenoid valve control switch) of slave unit 1 from [OFF] to [ON].
  4. Set slave unit 2 as slave unit 1:
    • Change DIP SW 3-3 / 3-4 (Outdoor unit address setting) of slave unit 2 from [ON / OFF] to [OFF / ON].
  5. Unplug the transmission connector from the master unit's PCB, or do not turn on power to the master unit at Step 6.
  6. Turn on the power and wait for 30 seconds or more.
  7. Check the LEDs:
    • Slave unit 1: Display of Inverter Communication error.
    • Slave unit 2: No error display.
  8. Backup operation is ready.
Heating-only setting: DIP SW 4-3 on slave unit 1 is changed from OFF to ON only for the heating backup operation when the master compressor is defective.

5. Heating backup - slave unit 1 compressor defective

  1. Stop the operation and turn off the power of all outdoor units.
  2. Fully close the 3-way valves (Liquid, Gas and Oil) of slave unit 1.
  3. Set up the system as two outdoor units:
    • Change DIP SW 4-1 / 4-2 (Connected number of slave units) of the master unit from [ON / OFF] to [OFF / ON].
  4. Set slave unit 2 as slave unit 1:
    • Change DIP SW 3-3 / 3-4 (Outdoor unit address setting) of slave unit 2 from [ON / OFF] to [OFF / ON].
  5. Unplug the transmission connector from slave unit 1's PCB, or do not turn on power to slave unit 1 at Step 6.
  6. Turn on the power and wait for 30 seconds or more.
  7. Check the LEDs:
    • Master unit: If the error is less than level 1, the system is ready for backup operation.
    • Slave unit 2: No error display.
  8. Backup operation is ready.

6. Quick DIP switch reference

ApplicationUnitDIP switchChange
Master defectiveSlave 1SW 3-3 / 3-4OFF / ON → OFF / OFF
Master defectiveSlave 1SW 4-1 / 4-2ON / OFF → OFF / ON
Heating, master defective onlySlave 1SW 4-3OFF → ON
Master or Slave 1 defectiveSlave 2SW 3-3 / 3-4ON / OFF → OFF / ON
Slave 1 defectiveMasterSW 4-1 / 4-2ON / OFF → OFF / ON
Final check: After power is restored, wait at least 30 seconds and confirm the LED indications described above before placing the system into backup operation.

Technical content reproduced from the supplied V Series service information. Follow the applicable service manual and site safety procedures when carrying out this work.