Single-Phase Connections: (See Diagram)
The tankless water heater was designed for single-phase, 240 volt operation on residential and light commercial electrical services. When properly connected, the load of the tankless water heater is automatically balanced across both legs (or poles) of the service. It doesn’t matter how many circuits the tankless water heater requires, the load will always be balanced on a single-phase service.
However, the only way the tankless water heater will work properly, is with both distinct poles or legs connected to each circuit. If the legs making up the circuit are from the same side of the service bus, then they will cancel and the resultant voltage will be zero (0) volts instead of 240 volts. This is usually referred to as "out-of-phase" or simply having the circuit wires crossed or out of sequence. Refer to the Single-Phase Diagram that illustrates the correct connections to the single-phase service in this section of the manual.
Three-Phase Connections: (See Diagram)
The tankless water heater will operate on 240 or 208 volt three-phase systems, that are commonly used in commercial and industrial buildings. However, the tankless water heater will not work on 480 volt three-phase or 277 volt phase-to-ground services. In three-phase applications, it is recommended to balance the tankless water heater load as much as possible, particularly, on 208 volt wye services.
Since the tankless water heater has an even number of heating elements and associated circuits, the load cannot be balanced evenly across a three-phase service. However, it is possible to spread the load across the three phases so that all the load of the tankless water heater is not on one phase. Refer to the Three-Phase Diagram that illustrates proper connections to the three-phase service in this section of the manual.
As shown in the diagram, model RA-28 requires four (4) 30 amp, double pole 240 or 208 volt circuits. The load of the four circuits can be connected to each phase of a three-phase service. Six of the eight legs from the four circuits can be distributed evenly across the three phases. The remaining two legs have to be connected to two phases, leaving one phase out of balance. In some buildings with three-phase service, there is a lighting load or single phase load that creates an imbalance anyway. So it may be possible to spread the load of the tankless water heater to the non-lighting load phase, which will help balance the load of the whole building.