Types And Maximum Allowable Length Of Cables - Mitsubishi Electric HP120TNU-A Service Handbook

[2-2 Types and Maximum Allowable Length of Cables ]

2-2

Types and Maximum Allowable Length of Cables

1. Wiring work
(1) Notes
1) Have all electrical work performed by an authorized electrician according to the local regulations and instructions in this man-
ual.
2) Install external transmission cables at least 5cm [1-31/32"] away from the power supply cable to avoid noise interference.
(Do not put the control cable and power supply cable in the same conduit tube.)
3) Provide grounding for the outdoor unit as required.
4) Run the cable from the electric box of the indoor or outdoor unit in such way that the box is accessible for servicing.
5) Do not connect power supply wiring to the terminal block for transmission line. Doing so will damage the electronic compo-
nents on the terminal block.
6) Use 2-core shielded cables as transmission cables.
Do not use a single multiple-core cable to connect indoor units that belong to different refrigerant systems. Doing so may result
in signal transmission errors and malfunctions.
Outdoor unit
TB TB TB TB
3 7 3 7
2-core shielded cable
TB TB TB TB
3 7 3 7
2-core shielded cable
TB3: Terminal block for indoor-outdoor transmission line TB7: Terminal block for centralized control
7) When extending the transmission cable, be sure to extend the shield wire.
8) When opening and closing the front panel of the control box, do not touch the internal parts. When inspecting the inside of the
control box, be sure to turn off the power of the unit at least 10 minutes beforehand and check that the electrolytic capacitor
voltage (inverter main circuit) has decreased to 20 V DC or less. (It takes about 10 minutes for the electricity to discharge after
the power is turned off.)
9) The control box (inside and rear) contains high-temperature parts. Be careful even after shutting down the power.
10) Before beginning service work, disconnect the fan board connector (CNINV) and the connector (CNFAN) on the INV board
or the connector (CNFAN2) on the capacitor board for the outdoor fan.
Before disconnecting and connecting a connector, check that the outdoor fan is not rotating and that the voltage of the main
circuit capacitor has decreased to 20 V DC or less. If the outdoor fan rotates due to a strong wind, there is a risk of an electric
shock because the main circuit capacitor will be charged. Refer to the wiring nameplate for details.
When the service work is finished, reconnect the connector (CNINV) on the fan board and the connector (CNFAN) on the INV
board or the connector (CNFAN2) on the capacitor board.
11) When connecting wires to TB7, check that the voltage is 20 V DC or less.
12) When the power is on, the compressor is energized even when it is stopped. Before turning on the power, disconnect the
power wires from the terminal block of the compressor and measure the insulation resistance of the compressor. Check that
the compressor does not have a ground fault. If the insulation resistance is 1 M or less, connect the power wires of the com-
pressor and turn on the power of the outdoor unit. (The compressor is energized to evaporate liquid refrigerant that has ac-
cumulated in the compressor.)
13) When connecting a system controller to the TB7 side of the outdoor unit, we recommend connecting a power supply unit for
transmission to the TB7 side.
If a system controller is connected to the TB3 side, up to three units can be connected.
A system controller can be connected to the TB7 side if the power supply switch connector is disconnected from CN41 and
then connected to CN40, but power will be supplied to the TB7 side even when the power of the outdoor unit is off so the
system controller may log an error and generate a warning.
14) When tightening the screws, take care that the screws are not loose or overtightened. A contact fault resulting from screw
looseness may cause the generation of heat and fire. Refer to the following page(s). [1-4 Precautions for Wiring]
2
- chapter 2
BC Controller Indoor unit
Remote Controller
Outdoor unit
BC Controller Indoor unit
TB TB TB TB
3 7 3 7
multiple-core cable
TB TB TB TB
3 7 3 7
Remote Controller
HWE18220_GB