The Short Answer
Most Singapore cold rooms beyond small chiller units require a three-phase 400V electrical supply, installed and certified by a Licensed Electrical Worker (LEW) registered with the Energy Market Authority. Backup power sizing must account for compressor starting current—not merely running wattage—or generators will fail to initiate the refrigeration system when needed.
Cold Room Electrical Planning at a Glance
| Facility Type | Typical Load | Power Supply | Backup Priority |
|---|---|---|---|
| Small chiller room (under 20 sqm) | ~3–5 HP, small unit | Single-phase 230V often sufficient | Moderate |
| Medium cold/freezer (20–80 sqm) | ~5–15 HP | Three-phase 400V typically required | High |
| Large multi-compartment facility | 20kW+ combined | Three-phase, dedicated submain/DB | Critical |
| Blast freezer cell | Oversized compressor | Three-phase, dedicated circuit | Critical |
Single-Phase vs Three-Phase
Small chiller compressors can operate on single-phase 230V supply. However, freezer rooms, larger chillers, and multi-compressor installations necessitate three-phase 400V—offering improved efficiency, lower per-phase current, and better handling of starting surges.
Licensed Electrical Work Requirements
Under Singapore’s Electricity Act, any new wiring, rewiring, or extension to an electrical installation must be carried out — or directly supervised — by a Licensed Electrical Worker (LEW) registered with the EMA. Installations exceeding 45kVA require separate EMA licensing. Contractors should provide LEW credentials before work commences.
Compressor Startup Current Impact
Direct-on-line compressors briefly draw somewhere in the region of four to six times their running current; soft starters reduce this to roughly 2.5–3× running current; VFDs limit surges to approximately 1–1.5×. Multiple simultaneous restarts after outages compound this effect, making generator sizing on running load alone insufficient.
Backup Power Sizing Components
Proper backup plans identify:
- Starting (surge) load with soft starter/VFD considerations
- Running (holding) load for compressor, fans, condensing unit
- Control and monitoring loads (controllers, alarms, data loggers, door heaters)
- Life-safety and operational loads (emergency lighting, compliance equipment)
Automatic transfer switches (ATS) paired with diesel generators provide standard automatic response during mains failure.
Common Electrical Mistakes
- Undersized cabling/breakers tripping on startup
- Non-dedicated circuits sharing databases with unrelated equipment
- Omitted surge protection despite Singapore’s lightning frequency
- Backup power sized on running load without startup considerations
- Delayed three-phase supply coordination with SP Group
Frequently Asked Questions
Single-phase or three-phase?
Small chillers (~3–5 HP) may use single-phase 230V. Most cold rooms, freezer rooms, and multi-compartment facilities require three-phase 400V for reliability.
Who performs electrical work?
A Licensed Electrical Worker (LEW) registered with the EMA must carry out or supervise all new wiring. Installations over 45kVA require separate EMA licensing.
Generator necessity?
Backup power depends on contents and outage tolerance. Well-insulated, fully-loaded freezers maintain safe temperatures for several hours on thermal mass. High-value, pharmaceutical, or cold chain storage typically justifies generators with automatic transfer switches.
Why larger generators?
Compressors draw far more current when starting than when running steadily. Multiple simultaneous restarts after power loss can spike demand well beyond running-load calculations, causing inadequately-sized generators to fail starting the compressor entirely.
Key avoidance points?
Undersized cables, shared circuits, missing surge protection, and backup power sized on running load without accounting for startup surges represent primary installation failures.