The technical guidance on this page reflects these published codes and standards, which your local authority (AHJ) adopts, amends, and enforces. It is educational, not engineering or legal advice — confirm the current requirements for your jurisdiction.
Two numbers on an equipment spec plate decide whether it will run in your building: voltage (120, 208, 240, 480) and phase (single or three). Get either wrong and the machine either won't run, runs weakly, or trips out. This is the most common reason a piece of equipment shows up and can't be installed — so it's worth understanding before you buy, not after.
Single-phase power delivers electricity on one alternating cycle. Three-phase delivers it on three overlapping cycles, so at any instant at least one phase is near peak. That makes three-phase smoother and more efficient for big motors and heating elements, which is why heavy equipment is built for it.
The most common commercial service is 120/208V three-phase, four-wire: you get 208V three-phase for the big stuff and 120V single-phase for outlets and lighting off the same panel. Larger buildings sometimes have 277/480V service. Older or small standalone spaces may only have single-phase 120/240V like a house — and that limits what you can install.
| Service | Phase | Typical use |
|---|---|---|
| 120/240V | Single-phase | Homes, small shops, light-duty equipment |
| 120/208V | Three-phase (4-wire) | Most restaurants — big loads + 120V outlets |
| 277/480V | Three-phase | Large buildings, industrial, big HVAC |
208V and 240V are often not interchangeable. Some equipment is dual-rated (208/240V) or field-configurable, but where it is not, a 240V-rated heating appliance run on 208V produces noticeably less heat (power drops with the square of voltage), and a 208V unit on 240V can overheat. Match the nameplate and the manufacturer-approved voltage configuration to the supply.
Light-duty and countertop gear is usually single-phase. Three-phase shows up on high-horsepower motors and high-wattage heat:
Many electric appliances are field-configurable for either phase at a given voltage, but the amp draw and required breaker differ — so the electrician needs the exact model before roughing in circuits.
If a building only has single-phase and your menu needs three-phase equipment, options include bringing in a new three-phase service from the utility (often expensive and slow), installing a phase converter, or choosing gas or single-phase versions of the equipment instead. Any of these changes the project cost, so confirm the building's service early. Total up your loads with the electrical load calculator, and if you're weighing fuels see gas vs electric equipment.
Every piece of equipment carries a data plate (nameplate) that tells you exactly what circuit it needs. Learn to read it and you'll avoid nearly every install surprise:
Give the electrician the model and this plate data before circuits are roughed in. The same oven model can ship in 208V single-phase and 208V three-phase versions that draw different amps and need different breakers — guessing wastes a service call and sometimes a permit re-inspection.
Tip: Before you sign a lease, get the panel's voltage, phase, and available amperage in writing. A space that looks perfect can need a costly service upgrade to run the equipment your concept requires. Check local requirements too.