The configurations you will actually meet
Single-phase 120/240V is the residential standard and it runs small commercial too. 120/208V three-phase wye is what most commercial buildings in Los Angeles have: 208V between any two phases for equipment, 120V to neutral for receptacles and lighting. 277/480V three-phase wye is the larger commercial and industrial standard, giving 480V for motors and larger equipment and 277V to neutral for lighting — which is why commercial lighting is so often 277V and why it cannot simply be swapped onto a 120V circuit. 240V delta still exists in older industrial buildings and carries a high leg that catches people out. Knowing which of these you have determines everything downstream.
Equipment connections and the mistake that costs most
The expensive version of this is a machine arriving on site that the building cannot run. A piece of equipment specified for 480V three-phase does not work on 208V by being wired differently, and a transformer or a different model is then an unplanned cost against a schedule that has already started. We check the nameplate requirements against the actual service before anything is ordered where we are asked early enough, and where we are not, we tell you straight away what the options are: a step-up or step-down transformer, a service change, or a different machine. Rooftop units, compressors, lifts, kitchen equipment and machine tools are where this comes up most.
Conversions, distribution and capacity
Where a building has single-phase and needs three-phase, that is a conversation with the utility about what is available in the street, not simply a change inside the building — and the answer varies by location. Sometimes a transformer or a phase converter is the practical route instead. Beyond the service itself we handle three-phase distribution: panels and switchboards, feeders sized for the run, motor circuits and disconnects, and the metering. If you are specifying equipment and are not certain what your building can support, that assessment is free and it is considerably cheaper than finding out after delivery.
Common questions
Can I run 480V equipment on a 208V service?
Not directly. It needs a step-up transformer, a service change, or different equipment. Which of those makes sense depends on the load, how much else you are running and what the utility can supply. We will price the realistic options rather than assume the largest one — but check before you order, because afterwards your choices narrow.
What is the high leg on a 240V delta service?
On a 240V delta with a center-tapped transformer, one phase sits around 208V to neutral rather than 120V. Connecting a 120V load to it damages equipment. It is marked orange by convention, but in old installations conventions were not always followed, which is why we verify rather than trust the color.
Can you get three-phase into a building that does not have it?
Sometimes. It depends entirely on what the utility has in the street at your location, and that answer varies block by block. Where it is not available or not economic, a phase converter or a transformer arrangement may do the job. We find out what is actually possible before anyone commits to equipment.
Technical planning notes & references
BEFORE WE QUOTE THE WORK
Confirm voltage and phase before ordering equipment
Use manufacturer requirements
208-volt and 480-volt systems are not interchangeable. A plug or enclosure does not establish supply requirements. Voltage, phase, load, starting characteristics and connection instructions guide the design. A transformer or utility change may be part of the solution.
Review the distribution path
Capacity, protection, disconnects, grounding, equipment ratings and routes all need assessment. Establish utility availability before promising a supply. Coordinate shutdowns and commissioning with the equipment supplier and property team.