8 Electrical Wiring
8.1 General
8.2 Power Supply Wiring
Power supply wiring design and installation should adhere to the following requirements:
Separate power supplies should be provided for the indoor units and outdoor unit.
Where five or more outdoor units are installed, additional residual current protection (leakage protection) should be
installed as shown in Figure 3-8.1.
All the indoor units in a system (i.e. all the indoor units connected to the same outdoor unit) should be tied into the
same power circuit with the same power supply, overcurrent and residual current protection (leakage protection) and
manual switch, as shown in Figure 3-8.2. Do not install separate protectors or manual switches for each indoor unit.
Powering on and shutting down all indoor units in a system should be done simultaneously. The reason for this is that
if an indoor unit that is running were to suddenly power off whilst the other indoor units continued running, the
evaporator of the powered-off unit would freeze since refrigerant would continue flowing to that unit (its expansion
valve would still be open) but its fan would have stopped. The indoor units that remain running would not get sufficient
refrigerant so their performance would suffer. Additionally, liquid refrigerant returning directly to the compressor from
the powered-off unit would cause liquid hammering, potentially damaging the compressor.
For outdoor unit power wire sizing and circuit breaker sizing, refer to Table 2-6.1 in Part 2, 6 “Electrical Characteristics”.
The refrigerant piping, power wiring and communication wiring are typically run in parallel. However, the
communication wiring should not be bound together with the refrigerant piping or power wiring. To prevent
signal interference, the power wiring and communication wiring should not be run in the same conduit. If the
power supply is less than 10A, a separation of at least 300mm between power wiring and communication wiring
conduits should be maintained; if the power supply is in the range 10A to 50A then a separation of at least 500mm