Mitsubishi Electric City Multi PQHY-P72 Service Handbook page 158

(2) Heat source unit (cooling only, heating only, cooling main and heating main modes)
"HO" / "PLEASE WAIT" blinks
on the remote controller
Protection function
self-holding cancelled.
1. 52C 4-way valve OFF
2. Inverter output 0Hz
3. All solenoid valves OFF
Cooling Only
*Note 1. For about 3 minutes after power on, search for the indoor unit address, for the remote controller address,
and for the group information will start. During this, "HO"/ "PLEASE WAIT" blinks on the display of the
remote controller. When the indoor unit to be controlled by the remote controller is missing,
"HO"/ "PLEASE WAIT" keeps blinking on the display of the remote controller even after 3 or more minutes
after power on.
*Note 2. The system may go into the error mode on either the indoor unit or the heat source unit side. The heat
source stops only when all of the connected indoor units are experiencing problems. The operation of even
a single indoor unit will keep the heat source unit running. The error will be indicated on the LED display.
*Note 3. The units will follow the operation mode commands from the BC controller
*Note 4. When the operation mode commands from the BC controllers are mixed (both cooling and heating), the
actual operation mode is determined by the heat source unit.
Start
Breaker NO
turned on
YES
*Note 1
Indoor units
registered to the
remote controller
NO
YES
2
NO
Operation
command
YES
fan
Operation
Cooling only, Heating only
mode
Mixture of units in cooling and heating
*Note 2
YES
Error mode
NO
52C ON
*Note 3
Mixture of units in cooling and heating
Operation
mode
Operation
mode
Heating Only Cooling Main
Operation command to the BC controller
2
- 149 -
Normal operation
Error
Unit in the stopped state
Error display on the
heat source unit LED
*Note 4
protection function
Operation command
to the BC controller
Heating Main
[ VII Control ]
Error stop
Self-holding of