Walk-In Cooler Electrical: Single-Phase vs Three-Phase, and 50 Hz Power Abroad

By Renato J. Alonso, Founder and President, Qube Cold Storage Solutions · Updated October 28, 2026

Most small walk-ins run on single-phase power: 208-230 V for the condensing unit and 115 V for a cooler evaporator. Larger systems and many commercial buildings use three-phase. A condensing unit is built for one or the other and cannot be converted, so confirm your building's voltage, phase and frequency in writing before we release the order.

What we assume if you don't tell us

Component	Default electrical
Condensing unit	208-230 V, single-phase, 60 Hz
Cooler evaporator	115 V, single-phase
Freezer evaporator (electric defrost)	208-230 V, single-phase
Door heaters, light, freezer pressure relief vent	Low-wattage circuit, on at all times

These are on every quote. Please confirm them, or tell us what your building has, before we release the order.

Which service does your building have?

Building service	Where you usually find it	What it means for your walk-in
120/240 V single-phase	Small shops, homes, some strip centers	Single-phase condensing units
120/208 V three-phase	Most commercial buildings	208-230 V units, single-phase or three-phase
277/480 V three-phase	Large buildings and warehouses	460 V units, or a transformer

The fastest way to know: a photo of the main panel label, or one line in writing from your electrician with voltage, phase and frequency.

Single-phase or three-phase?

• Single-phase covers most small coolers and freezers. It is the only choice where the building has no three-phase.
• Three-phase motors start easier and draw less current per wire. If the building has it, it is usually the better choice for larger condensing units.
• Some sizes only come in three-phase. Larger condensing units, around 6 HP and up, are often three-phase only.
• Evaporators usually stay single-phase even when the condensing unit is three-phase. That is normal, not a mistake on the drawing.
• "208-230 V" covers both 208 V and 230/240 V service. You don't need different equipment for each.

Circuits to plan

1. A dedicated circuit for each condensing unit, with a disconnect as your code requires.
2. A circuit for each evaporator.
3. A circuit for the door heaters, light and, on freezers, the pressure relief vent. These stay on all the time.
4. On systems with an A2L refrigerant (a mildly flammable class), power and wiring for the refrigerant detection sensor and the safety shutoff valve.

Wire and breaker sizes come from the nameplate MCA (minimum circuit ampacity) and MOP (maximum overcurrent protection). Both are on the refrigeration submittal we send with the order. Your electrician sizes the work from those numbers.

50 Hz power outside the U.S.

A 60 Hz motor on 50 Hz power turns about 17% slower. The compressor loses capacity and the motors run outside their rating. If your country is on 50 Hz, the refrigeration has to be selected and built for 50 Hz from the start. See our article on shipping walk-ins to the Caribbean and Latin America for a country-by-country table.

From the field

A multi-room project came to us specified as single-phase. The equipment was ordered that way, and only after it arrived on site did the building turn out to have three-phase service. Seventeen condensing units and evaporators had to be sorted unit by unit: photo of every nameplate, KEEP or EXCHANGE on each, and the three-phase service confirmed in writing before a single replacement was released. It worked out because most of the equipment was still sealed. It still cost the job time. That is why we now confirm site voltage and phase in writing on every order before it goes to production. One line from your electrician is all it takes.

Questions people ask

Can a single-phase condensing unit run on three-phase power?

Not as delivered. Order the phase your building has.

Does a cooler need a 220 V circuit?

The condensing unit usually does. A cooler evaporator usually runs on 115 V.

Who wires it?

A licensed electrician, from the nameplate data on our submittal.