240v如何從120 / 208v饋電中獲得


我的公寓饋線是120 / 208v 4線(加地線)。

公寓提供120 / 240v服務。




the advantage of feeding a complex with 3 phase is the phases can be split up and balanced allowing smaller feeders at the main. The only negative the water heater will be slightly slower to heat up same with the oven or range and dryer. The dryer motor is usually 120 v so that is not a problem. In residential complexes there are normally very few 240 motor loads, a 240 motor will usually work ok , remember the voltage described by code is 208 / 230 so we are right at +-10% so most motor loads won’t have a problem. The big advantage comes when the complex has elevators or provides hot water or cooling 3 phase power is more efficient than single phase .

Today 208 is the common “low voltage” 3 phase years back it was 230v


It isn't.

120/240V is a 240V single phase supply, center tapped to produce a "split phase" with 120V between either side to neutral, and 240V between the two hot lines.

120/208V is two phases from a three-phase supply. There is 120V from either phase to neutral, and 208V between the phases.


Apartments have 120/240v service.

Says who? Apartments have the service they have. 120/240V implies a “split-phase” service which is universal for single-family dwellings outside NYC, but apartment buildings are actually commercial and are often wired to commercial standards. It really depends what the power company has in the area, and what they are willing to provision to the development.

My apartment house feed is 120/208v 4 wire (plus ground) wye connected.

Well, then, that is that. Your apartment does not have 240V service.

Water heater, range and dryer are resistive loads, and they will work alright on 208V instead of 240V, just will heat at a 25% reduced capacity. Consider that when sizing those appliances, although it’s usually not a big deal.

Motor loads (A/C; heat pump water heater or dryer) will care about 208V vs 240V, but many of them can be internally jumpered for either voltage. Shop carefully!


first, thanks to everybody. i came into this with a mistaken impression based on a lifetime in single-family homes with 120/240 service (at 180 degrees). my apartment indeed has 120/208 at 120 degrees. (the service panel, etc look the same). i imagine 1/3 of the apartments are on AB, 1/3 on AC and 1/3 on BC. as others have said, heating appliances take 30% longer to come up but achieve the target temperature because they are thermostat-limited. i greatly appreciate all the interest and support. enjoy yourselves and stay safe!