240V to 208V Buck-Boost Transformer — Step-down, Single Phase
See how a 240V to 208V single phase buck-boost transformer corrects voltage and how to select the proper model.
Choosing a 240V to 208V transformer
Most people arrive at 240V to 208V asking a version of the same question: can this give me 208Y/120? The answer is no, and it belongs at the top of the page. A buck-boost transformer is an insulating transformer reconnected as an autotransformer. It shifts line-to-line voltage and nothing else. It cannot derive a neutral, so it cannot turn a three-wire 240V supply into a four-wire 208Y/120 system, and no connection diagram will make it do so. What a 240V to 208V buck-boost transformer does do, and does cheaply, is take equipment built for a 208V service and let it run correctly on a 240V supply. Single-phase and three-phase units are offered in 10, 15, 20, 30, 40, 50 and 60 amp ratings.
Equipment ends up on the wrong service for ordinary reasons. Somebody ordered the 208V voltage code because the space was assumed to be a typical 208Y/120 tenant suite. A machine got moved. A used unit came out of a facility with a different service. The nameplate did not change on the way over.Packaged HVAC and refrigeration ordered on the 208V code and delivered to a building fed 240V single-phase or 240V delta.Commercial kitchen equipment specified 208V, common with chains that standardize on one voltage nationally regardless of what any site is actually fed.Equipment relocated from a leased suite into an owner-occupied building, or out of a strip center into a freestanding building on its own transformer.Used and auction machinery bought out of a commercial space and installed in a shop, farm or light industrial building.Dental compressors, vacuum pumps, imaging equipment and laboratory gear built around a 208V supply.Point-of-use water heaters and process heaters nameplated 208V, which are the least forgiving loads in the group.Rural, agricultural and older industrial buildings account for a disproportionate share, because a 240V service is what is there and it is not going to change to accommodate one machine.