Electrical Design for Industrial Buildings

What You Need to Know

Industrial buildings place unique demands on electrical infrastructure. Factories, warehouses, and processing facilities require significantly more power than commercial offices, with loads driven by three-phase motors, process equipment, compressed air systems, and heavy-duty HVAC plant. A typical industrial facility in Sydney draws between 500 kVA and 5,000 kVA, often requiring a dedicated high voltage (HV) supply and on-site transformer.

The electrical design must account for maximum demand calculations, power factor correction, hazardous area classifications, emergency power provisions, and industrial-grade cable management. All of this sits under AS/NZS 3000:2018 (the Wiring Rules), with additional standards applying to hazardous areas, lightning protection, and specific equipment types.

Getting the electrical design wrong on an industrial project causes expensive problems. Undersized transformers cannot be easily upgraded. Poor power factor attracts ongoing network penalties. Missing a hazardous area classification exposes the owner to serious safety and compliance risk. The cost of electrical infrastructure on an industrial project typically represents 8% to 15% of the total construction cost, making early and accurate design critical.

• AS/NZS 3000:2018 (Wiring Rules) governs all electrical installations. Industrial buildings must comply with the same fundamental wiring requirements as any other building, plus additional clauses for industrial equipment, motor circuits, and high-current installations. (AS/NZS 3000:2018)
• Maximum demand must be calculated per AS/NZS 3000 Section 2. For industrial loads, diversity factors are lower than commercial buildings because process equipment often runs at full load simultaneously. Motor starting currents and duty cycles must be included in the calculation. (AS/NZS 3000:2018, Section 2)
• Cable sizing must comply with AS/NZS 3008. Industrial cable runs are often longer and carry higher currents than commercial installations. Voltage drop, current carrying capacity, and short-circuit rating must all be verified. Cable derating factors apply for grouped cables in tray and elevated ambient temperatures. (AS/NZS 3008.1.1)
• Hazardous areas must be classified under AS/NZS 60079. Any facility handling flammable gases, vapours, dusts, or fibres requires a hazardous area classification study. All electrical equipment in classified zones must be Ex-rated and installed to the relevant part of the AS/NZS 60079 series. (AS/NZS 60079.10.1, AS/NZS 60079.10.2)
• Lighting must comply with AS 1680 for the specific industrial task. Warehouses, manufacturing areas, and loading docks each have different minimum maintained illuminance levels. High bay LED luminaires are standard for ceiling heights above 6 m. (AS 1680.1, AS 1680.2.4)
• Earthing systems must comply with AS/NZS 3000 and AS 1768. Industrial buildings require a comprehensive earthing system including main earthing conductor, equipotential bonding of metallic structures, and lightning protection where required by the risk assessment. (AS/NZS 3000:2018, AS 1768)
• Emergency power systems must comply with AS/NZS 3010. Essential services, fire systems, and critical process loads require standby power from generators or UPS systems with automatic transfer switching. (AS/NZS 3010)
• Energy metering for large sites falls under the NCC and network distributor requirements. Sites above 500 kVA typically require interval metering and may require sub-metering of major load groups for energy management purposes. (NCC 2025 Part J9, Distributor Connection Standards)

Power supply and transformer sizing. The first decision on any industrial project is whether the site needs a high voltage (HV) or low voltage (LV) supply. In NSW, Ausgrid and Endeavour Energy generally require an HV supply for loads above 500 kVA. This means the owner must provide a substation with one or more transformers stepping 11 kV down to 415/240 V. Transformer sizing is based on the maximum demand calculation plus a growth allowance of 10% to 20%. Oversizing wastes capital. Undersizing creates a bottleneck that is expensive to fix after construction.

Maximum demand for industrial loads. Industrial maximum demand calculations differ from commercial ones because diversity factors are much lower. A warehouse with 20 dock levellers, a cold storage area, and packaging machinery may have 80% to 90% of connected load running simultaneously during peak production. Motor starting currents, which can be 6 to 8 times full load current for direct-on-line starters, must be assessed for their impact on voltage dip at the main switchboard. Variable speed drives (VSDs) reduce starting current but introduce harmonic distortion that affects other equipment on the same supply.

Three-phase power distribution. Industrial buildings distribute power at 415 V three-phase from the main switchboard (MSB) through sub-main distribution boards (SDBs) to final circuits. Motor control centres (MCCs) are dedicated switchboards housing motor starters, VSDs, protection devices, and control wiring for process equipment. The MCC layout directly affects cable routing, maintenance access, and future expansion. Locating MCCs close to their associated equipment reduces cable costs and voltage drop but requires consideration of environmental conditions such as dust, heat, and vibration.

Power factor correction. Industrial facilities with large motor loads typically have a power factor between 0.70 and 0.85 lagging. Network distributors impose financial penalties when the power factor at the point of supply drops below 0.90 or 0.95. Automatic capacitor banks are the standard solution, switching capacitor steps in and out based on real-time reactive power demand. Where VSDs generate significant harmonics, detuned reactors or active harmonic filters must be used to prevent capacitor resonance, which can damage equipment and cause nuisance tripping.

Emergency and essential power. Industrial buildings require standby power for fire systems, emergency lighting, and smoke control. Beyond code-minimum requirements, many industrial facilities also need backup power for critical process loads such as control systems, refrigeration, and safety interlocks. Diesel generators are the standard solution, sized to carry the essential load with automatic transfer via an ATS within the code-required time (typically 10 seconds for fire systems). UPS systems protect sensitive electronic equipment from power interruptions and provide ride-through during the generator start-up period.

Industrial lighting design. Warehouses and factories with ceiling heights of 8 m to 15 m require high bay LED luminaires. AS 1680.2.4 specifies maintained illuminance levels: 160 lux for general warehousing, 240 lux for packing and dispatch, 400 lux for inspection and quality control areas, and 600 lux for fine assembly. Lighting controls including occupancy sensors and daylight harvesting reduce energy consumption by 30% to 50% in areas with intermittent use or significant roof glazing. Emergency and exit lighting must comply with AS 2293 with maintained fittings in hazardous areas.

Cable management. Industrial environments demand robust cable management. Heavy-duty galvanised cable tray is standard for power and control cables in open warehouse and factory areas. Cables in floor-level traffic zones require concrete-encased conduit or below-ground trenching. In areas with chemical exposure, stainless steel or fibreglass cable tray may be required. Cable segregation between power, control, and data circuits must be maintained per AS/NZS 3000 to prevent electromagnetic interference with control systems.

Hazardous area classification. Facilities handling flammable substances require a formal hazardous area classification study under AS/NZS 60079.10. This identifies zones (Zone 0, 1, 2 for gases; Zone 20, 21, 22 for dusts) and specifies the extent of each zone. All electrical equipment within classified zones must be certified Ex-rated for the relevant zone, gas group, and temperature class. Common industrial hazardous areas include paint spray booths, battery charging rooms, grain storage, chemical dosing areas, and fuel storage facilities. The classification study must be completed before the electrical design begins, as it fundamentally affects equipment selection, cable installation methods, and costs.

Earthing and lightning protection. Industrial buildings, particularly those with large metal roof areas, tall structures, or storage of flammable materials, require a risk assessment for lightning protection under AS 1768. Where lightning protection is required, a system of air terminals, down conductors, and earth electrodes is designed to safely conduct lightning current to ground. The earthing system must integrate with the electrical installation earthing, structural steel bonding, and any cathodic protection systems. A well-designed earthing grid also reduces step and touch potentials, protecting personnel during earth fault conditions.

Energy metering and sub-metering. Large industrial sites benefit from sub-metering of major load groups including production equipment, HVAC, compressed air, lighting, and office areas. Sub-metering enables energy benchmarking, identifies waste, and supports ISO 50001 energy management certification. Modern metering systems with Modbus or BACnet connectivity integrate with building management systems (BMS) for real-time monitoring and automated reporting.

Solar PV integration. Industrial rooftops are ideal for solar PV due to large unshaded roof areas and daytime load profiles that align with solar generation. A typical industrial roof can accommodate 100 kW to 500 kW of PV capacity. The electrical design must address inverter sizing, grid connection requirements, export limiting (if required by the distributor), and protection coordination with the existing LV switchboard. Solar PV offsets daytime energy costs and can reduce maximum demand charges if paired with battery storage or load management.

Electrical safety. Industrial electrical installations present heightened arc flash and electrocution risks due to high fault currents at the main switchboard. An arc flash study per IEEE 1584 determines the incident energy at each switchboard and establishes the required personal protective equipment (PPE) ratings and safe working distances. Isolation and lockout/tagout procedures must be documented and integrated into the electrical design through clearly labelled isolation points, lockable circuit breakers, and maintenance access provisions at switchboards and MCCs.