Installation
SiE33-003
48
General Information
Power Supply
(Cabling of Main
Power Supply)
1. Choosing a circuit breaker
The power supply work must conform to local regulations. In Japan, the relevant regulations are the MITI
ordinance determining technical standards for electrical equipment, and the Internal Wining Provisions.
a) The indoor unit circuit breakers
In accordance with the provisions for internal wiring (JEAC8001-1986), power may be supplied by
means of crossover lines between the indoor units in a single system branch circuit.
When using high static pressure indoor units the fan motors must have a large capacity. Single phase
220~240V branch circuits are therefore required for each indoor unit.
Example: Up to 10
×
2.5HP indoor units or 5
×
5HP indoor units can be wired together.
b) The outdoor unit circuit breaker
A separate circuit breaker must be fitted for each unit.
The motors incorporated into air conditioning system compressors are treated as special motors under
the internal wiring provisions. The values which apply to normal motors are thus somewhat variance
with those which apply to such compressor motors. You are recommended to adhere strictly to the
procedures laid down in the technical materials included in, for example, the system design manuals.
Calculation of load (Refer to local regulation.)
With respect to the calculation of load for motors with special applications such as elevator, air conditioner
and refrigerator motors, not only must the rated current be shown on the name plate of the said motor or
piece of apparatus but it must also included all special characteristics or applications.
Note:
The rated current for package air conditioners which use special purpose built-in compressor motors in
their compressors in 1.2 times the operating current shown on the name plate.
2. Cable size
The thickness of the cables in the circuits (branch circuits) providing the main power supply to each item of
apparatus must satisfy the following conditions:
1. To have a current tolerance of 40% or more of the rated current of the overcurrent circuit breaker
(wiring circuit breaker, etc.).
2. To have a current tolerance of 125% or more of the rated current in cases where the rated current of the
apparatus is 50A or less.
3. To have a current tolerance of 110% or more of the rated current in cases where the rated current of the
apparatus is more than 50A.
4. To satisfy voltage drop standards.
3. Separation of control and power supply cables
If control and power cables are run alongside each other then there is a strong likelihood of
operational faults developing due to interference in the signal wiring caused by electrostatic and
electromagnetic coupling.
Branch circuit facility (Internal wiring provisions
305-2)
The motors must be set up with a dedicated branch
circuit for each unit. However, where they
correspond to any of the following situations, this
limitation does not apply.
When used in a 15A branch circuit of a 20A
circuit breaker branch circuit
Note: It is recommended that the total rated
capacity of the motors set up in a 15A branch circuit
or a 20A circuit breaker branch circuit should be no
more than 2.2kW.
Si33-003.book Page 48 Monday, June 25, 2001 9:06 AM
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