Commercial buildings need electrical distribution that fits limited space, occupied areas and phased construction. The design must balance transformer efficiency, fire strategy, acoustic performance, ventilation, maintenance access and future tenant demand. Equipment should be selected from the building load schedule and room conditions, not from floor area alone.
Locate transformation close to the load—carefully
Dry-type transformers are often placed inside electrical rooms because they avoid oil containment and shorten low-voltage cable runs. Cast-resin construction can suit humid or demanding indoor environments, while VPI designs may be appropriate for clean, controlled rooms. The enclosure, ventilation and sound requirement must be coordinated with the architectural layout.
Questions that affect equipment selection
- What is the diversified demand, largest motor load and expected tenant growth?
- Is the transformer room naturally ventilated or mechanically cooled?
- What fire-resistance, smoke and emergency-egress requirements apply?
- Are offices, hotel rooms or other noise-sensitive spaces adjacent to the room?
- Does the utility require an outdoor pad-mounted transformer or customer-owned indoor substation?
- What maintenance route is available for future transformer or switchgear replacement?
Typical distribution arrangements
| Building condition | Possible arrangement | Key review |
|---|---|---|
| Utility underground service | Pad-mounted transformer with LV main switchboard | Utility interface, pad opening, metering and service clearances |
| Customer MV service | MV switchgear, indoor dry transformer and LV switchboard | Protection ownership, room ventilation and fire separation |
| Large campus or mixed-use site | Multiple substations distributed by load zone | Ring or radial MV topology, sectionalising and phased expansion |
Efficiency, harmonics and sound
Lifecycle evaluation should consider no-load loss during lightly occupied periods and load loss at expected demand. LED drivers, lifts, variable-speed HVAC and IT loads can increase harmonic current and neutral loading. Where sound is critical, the required sound level and measurement basis should be stated rather than relying on a general “low-noise” description.
RFQ baseline
Provide the load schedule, utility service data, transformer location, room temperature and ventilation, available dimensions, fire and acoustic requirements, primary and secondary voltages, standard, quantity and project programme.