Electrical installations must be designed and installed so that they comply with IEE requirements and all applicable national or local codes and standards.

There are three voltages commonly used in HVAC work. These are 380V 3ph, 220V 1ph, and 24V. In addition low voltage signal wiring from sensors etc must be considered.

• Different voltages must never be mixed in the same cable.
• The speed should be reduced to 3 m/s at the approach to grilles and louvres
• Use screened cable for all sensor and signal wiring.
• Electrical cables must be sized to carry the rated current.

If a cable is too small then there may be an excessive voltage drop. In order to size the cable the rated power load and the length of cable must be known. Cable sizes can then be selected according to the following charts.

Power Wiring

This is required to supply motors and resistance loads etc.

Power wiring is normally 220 V AC or 380 V AC.

The size (cross section) of the cable required varies with the voltage, power load and cable length.

Sensor Wiring

Low voltage DC signals from sensors should be transmitted in separate screened cables. Minimum cable size 0.5mm ²