Three-phase supply upgrades: when your building has run out of power

Older commercial buildings were wired for the loads of their time. Add air conditioning, EV charging, catering equipment or modern plant and the supply, not the building, becomes the constraint.

Signs you are at capacity

Nuisance tripping of the main protective device, voltage drop under load, a distribution board with no spare ways, and contractors declining to add circuits are all indicators that the supply is fully committed.

The load survey

Before anything is specified, the existing demand is measured over a representative period, including peaks. Diversity is then applied to give a realistic maximum demand rather than a worst-case sum of every nameplate rating.

Single-phase to three-phase

A three-phase supply carries more power over the same cable sizes and balances heavy loads across phases. For most sites adding significant plant, it is the difference between an installation that works and one that runs permanently near its limit.

Working with the DNO

The Distribution Network Operator owns everything up to the supply cut-out. An application produces a quotation and a connection date, and network reinforcement can extend that timescale considerably. Applying early is the single biggest saving on the programme.

Inside the building

New main switchgear, submains, containment and earthing arrangements usually follow the supply upgrade. Planning these together, with an agreed changeover window, keeps the building operational through the transition.