Types And Maximum Allowable Length Of Cables - Mitsubishi Electric PQHY-P72ZLMU-A Service Handbook

[ II Restrictions ]

[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 heat source unit as required.
4) Run the cable from the electric box of the indoor or heat source 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.
Use a separate 2-core control cable for each refrigerant system. Do not use a single multiple-core cable to connect indoor
units that belong to different refrigerant systems. The use of a multiple-core cable may result in signal transmission errors and
malfunctions.
Heat source 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-heat source transmission line TB7: Terminal block for centralized control
7) When extending the transmission cable, be sure to connect the shield.
8) When opening or closing the front cover of the control box, keep out of contact with the internal parts.Before inspecting the
inside of the control box, turn off the power, leave the unit turned off for at least 10 minutes, and check that the voltage of the
electrolytic capacitor (inverter main circuit) has dropped to 20 VDC or less.
9) Control boxes house high-voltage and high-temperature electrical parts. Use caution not to come in contact with them.
10) When the unit is turned on, the compressor will remain energized even when it is stopped to vaporize the liquid refrigerant
that accumulates in the compressor. Disconnect the power supply cable from the compressor terminal block, and measure
the insulation resistance of the compressor.Check that the compressor is not ground faulted.If the insulation resistance is 1
M or below, reconnect power supply to the compressor, and turn on the power.
11) Read Chapter I [13] Precautions for servicing, and tighten screws to the appropriate torque.Loose screws and poor contact
can result in overheating and fire.
(2) Control wiring
Different types of control wiring are used for different systems.
Refer to section "[5] An Example of a System to which an MA Remote Controller is connected - [7] An Example of a System
to which both MA Remote Controller and ME Remote Controller are connected" before performing wiring work.

Types and maximum allowable length of cables

Control lines are categorized into 2 types: transmission line and remote controller line.
Use the appropriate type of cables and observe the maximum allowable length specified for a given system. If a given system
has a long transmission line or if a noise source is located near the unit, place the unit away from the noise source to reduce
noise interference.
HWE15150
BC Controller Indoor unit
Remote Controller
Heat source unit
BC Controller Indoor unit
TB TB TB TB
3 7 3 7
multiple-core cable
TB TB TB TB
3 7 3 7
- 19 -
Remote Controller
GB