Distribution Board Sizing: Single Phase vs. Three Phase, and Why It Matters
Undersizing a distribution board is one of the most expensive mistakes to fix after handover. Here's how load calculation actually works.
A distribution board sized for today's load with no headroom for tomorrow's tenant fit-out is one of the most common — and most expensive to retrofit — mistakes in commercial electrical design.
Single Phase Covers Less Than You'd Think
Single-phase boards suit small commercial units and residential-scale loads, but once you're running significant motor loads, HVAC plant, or a building with genuinely balanced three-phase demand, single-phase distribution becomes a bottleneck fast — both in capacity and in load-balancing complexity.
Three Phase Isn't Just "More Capacity"
Three-phase distribution balances load across phases, which matters for both capacity and for equipment that specifically requires three-phase power (larger motors, certain HVAC compressors). A three-phase board also gives you room to add single-phase sub-circuits without re-engineering the whole board.
Way Count: Plan for the Fit-Out, Not Just Day One
A 4-way board that's fully populated at handover leaves zero room for a tenant's future fit-out — every additional circuit becomes a board replacement instead of a spare-way connection. Specifying two or three spare ways at design stage costs little and saves a full board swap later.
What We Stock
Our distribution board range covers single-phase (4-way and 8-way) and three-phase (12-way) configurations, plus standalone energy meter boxes with tamper-proof sealing for sub-metered tenancies.