Will a Single Phase Air Conditioner Work With Three Phase Power?

By Michael Logan, eHow Contributor

 
 
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A 120-volt air conditioner won't have any trouble with a three-phase supply.

Most residential electric utility customers only have a single-phase electrical supply, but some apartment buildings use three-phase and distribute two of the phases to each apartment. Small appliances that need 110 to 120 volts will not have any trouble with the supply in an apartment building. Some large appliances that require 220 to 240 volts may have problems with certain three-phase voltage supplies if they have heating elements, but appliances with electric motors probably won't be affected.

1. Connection Considerations

   • A three-phase connection requires three hot wires, one for each phase of the current. Air conditioners that operate on single-phase current will require either a hot and neutral connection, or a connection with two hot wires. There is no way, without significant modification, to connect a single-phase air conditioner to all three-phases of a three-phase supply.

     Most three-phase supply systems include connections for lighting circuits and single-phase appliances. These systems exist in both residential apartment buildings and in some commercial environments to operate appliances such as air conditioners.

   Apartment Buildings

   • The three-phase current supply in certain apartment buildings provides two phases of current, plus a neutral wire, to each apartment. The current between any hot wire and a neutral wire is approximately 120 volts and is a single-phase circuit.

     A second type of circuit found in apartment buildings comes from the three-phase supply for operating appliances such as electric ranges and larger air conditioners. Two wires from the three-phase supply provide a total of 208 volts.
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   Air Conditioner Requirements

   • Manufacturers design and build appliances, including air conditioners, to operate on specific voltages. A typical window air conditioner may require either 120 or 208/230 volts of single-phase current. Most central air conditioning units require 208/240 volts of current.

     Manufacturers also take into consideration that the appliances they build will operate in different types of environments. Some utility customers have 120-240 volt single-phase electrical systems; others have 120-208 volt systems derived from a three-phase supply. Still others -- mainly commercial customers -- have 120-230 volt systems, also from a three-phase supply.

   Correct Voltage

   • An air conditioner designed to run on single-phase current won't have any trouble operating off a three-phase supply, as long as it connects to the correct voltage. In an apartment building, a 120-volt circuit is a single-phase circuit. A 208- or 230-volt circuit in the same building will operate single-phase appliances -- including air conditioners -- designed for the higher voltage, even though the voltage comes from a three-phase supply.

     The connection to the air conditioner does have to meet the appliance's voltage requirements. It is important to note that in some commercial three-phase systems, not all the hot wires are the same. Some hot-to-hot connections provide a much higher voltage than 230 volts, and some hot-to-neutral connections can exceed 120 volts.