A cold room is only as reliable as the electrical supply behind it. Here's how to plan power supply, wiring compliance and backup power before your compressor is ever switched on.
Most cold rooms in Singapore beyond a small chiller unit need a three-phase 400V electrical supply, installed and certified by a Licensed Electrical Worker (LEW) registered with the Energy Market Authority (EMA), on a dedicated circuit sized well above the compressor's steady running current. Backup power, where needed, has to be sized around the compressor's starting current — not just its running wattage — or the generator will fail to start the refrigeration system exactly when you need it most.
Electrical planning is one of the most commonly underestimated parts of a cold room project. Get it wrong and the symptoms show up later as tripped breakers, a generator that can't actually start the compressor, or a failed EMA inspection that delays your handover. Get it right from the design stage and it's a one-time cost that quietly protects everything the cold room is built to store.
| Facility Type | Typical Compressor Load | Power Supply | Backup Power Priority |
|---|---|---|---|
| Small chiller room (under 20 sqm) | Roughly 3–5 HP, small condensing unit | Single-phase 230V often sufficient | Moderate — chilled stock tolerates short outages |
| Medium cold/freezer room (20–80 sqm) | Roughly 5–15 HP | Three-phase 400V typically required | High — frozen stock at risk within hours |
| Large multi-compartment facility | Multiple compressors, combined load often 20kW+ | Three-phase, dedicated submain/DB | Critical — simultaneous restart current must be planned for |
| Blast freezer cell | Oversized compressor for rapid freeze cycle | Three-phase, dedicated circuit | Critical — highest starting current demand on site |
These figures are general planning ranges, not a substitute for a proper load calculation. Actual compressor size, phase requirement and cable sizing depend on your specific room dimensions, insulation, door traffic and target temperature — always get a site-specific electrical load assessment before finalising your design.
A single-phase 230V supply can run a small chiller compressor comfortably, which is why some compact walk-in chillers in cafes or small F&B outlets get by on standard commercial single-phase wiring. Once you move into freezer rooms, larger chillers, or anything with multiple compressors, three-phase 400V power becomes necessary — three-phase motors run more efficiently at higher loads, draw lower current per phase for the same power output, and handle the starting surge of a larger compressor far more gracefully than a single-phase circuit ever could.
If your building doesn't already have a three-phase supply at the point where the cold room will sit, that's a conversation to have with your electrical contractor and, where the load is significant, with SP Group very early in the project — not after the refrigeration equipment has already been ordered.
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. LEW licences come in three classes (Electrician, Electrical Technician, and Electrical Engineer) with the scope of work each is permitted to certify scaling with qualification: a Licensed Electrician, for example, is generally limited to installations up to 45kVA and 1,000 volts.
Where the approved load of the installation exceeds 45kVA, a separate EMA electrical installation licence is also required, and you cannot apply for or hold one without engaging an LEW. In practice, this means your cold room contractor should be coordinating directly with a licensed electrician or engineer on the DB (distribution board) sizing, cable routing and load submission — not leaving it to unlicensed general labour, however capable they might seem on site.
Pro Tip
Ask your contractor for the name and licence class of the LEW who will certify the installation before work starts, not after. It's a normal, reasonable question, and any contractor doing this properly will have the answer ready.
This is the single most common mistake we see in backup power planning: sizing a generator against the compressor's running current, then discovering it can't actually start the compressor at all. Refrigeration compressors draw significantly more current the instant they start than they do once running steadily. A direct-on-line (DOL) started compressor can briefly draw somewhere in the region of four to six times its running current; soft starters bring that down to roughly 2.5–3 times running current, and variable frequency drives (VFDs) can limit the surge to closer to 1–1.5 times running current.
The problem compounds in facilities with multiple compressors. After a power interruption, several units can try to restart at the same moment, and the combined starting current can spike well past anything the running-load total would suggest. A generator or UPS sized purely on nameplate running watts will frequently trip out, stall, or simply fail to bring the compressor up to speed — leaving you with a generator that runs, but a cold room that doesn't.
A proper backup power plan for a cold room accounts for more than the compressor alone. The load schedule should separately identify:
For an automatic response to a power failure, a diesel generator paired with an automatic transfer switch (ATS) is the standard setup for facilities that can't tolerate manual intervention during an outage — the ATS senses the loss of mains power, starts the generator, and switches the load over within seconds, minimising the time the cold room spends without active cooling.
Whether you need backup power at all comes down to what's inside the room and how long you can afford to lose active refrigeration. A well-insulated, fully-loaded freezer room can often hold safe temperature for several hours on thermal mass alone during a short outage. For high-value stock, pharmaceutical or cold chain storage — see our guide on refrigerant choices for cold rooms for related compliance considerations — or any operation where a prolonged outage means real financial loss, backup power moves from "nice to have" to a core part of the design.
Every cold room project we quote includes a proper electrical load assessment as part of the design phase — compressor starting and running current, cable and breaker sizing, phase requirement, and a backup power recommendation where relevant — coordinated with a Licensed Electrical Worker from day one, not bolted on after the refrigeration system is already speced. This keeps the installation compliant, avoids nasty surprises at EMA inspection, and means your generator (if you choose one) will actually start your compressor when it matters.
Does a cold room need single-phase or three-phase power?
Small chiller rooms with a compressor under roughly 3-5 HP can often run on a single-phase 230V supply. Most cold rooms and freezer rooms above that size, and virtually all multi-compartment or blast freezer facilities, need a three-phase 400V supply because the compressor motors, starting current and overall load are too high for a single-phase circuit to handle reliably. Always confirm the exact requirement against the specific compressor and condensing unit your contractor specifies.
Who is allowed to do the electrical wiring for a cold room in Singapore?
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 Energy Market Authority (EMA). Installations with an approved load exceeding 45kVA also require a separate EMA electrical installation licence. Your cold room contractor should coordinate this directly with a licensed electrician or engineer, not leave it to unlicensed labour.
Do I need a backup generator for my cold room?
It depends on what you're storing and how long you can tolerate an outage. A short power cut is rarely a problem for a well-insulated, fully-loaded freezer room, which can often hold safe temperature for several hours on its own. But for high-value stock, pharmaceutical or cold chain storage, or any facility where a prolonged outage means spoiled inventory or a food safety breach, backup power (generator or UPS with automatic transfer switch) is a reasonable and often necessary investment.
Why does a cold room need a bigger generator than its running load suggests?
Refrigeration compressors draw far more current when starting than when running steadily — a direct-on-line compressor can briefly draw around 4-6 times its running current. If a facility has multiple compressors that all try to restart at once after a power cut, that starting current can spike well beyond what the running load alone would suggest, which is why generators sized only on nameplate running watts frequently fail to start the compressor at all.
What electrical mistakes should I avoid when installing a cold room?
The most common issues we see are undersized cabling or circuit breakers that trip under compressor starting current, no dedicated circuit for the refrigeration system (sharing a DB with other equipment), skipping surge protection in a country with frequent lightning activity, and backup power sized on running load without accounting for compressor startup current or simultaneous restart of multiple units.
We'll assess your compressor load, phase requirement and backup power needs as part of your project design — coordinated with a Licensed Electrical Worker from the start, so there are no surprises at inspection.
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