Using WattsOn in Single/Split phase installations

The WattsOn meter was natively designed for three-phase applications, however because of its flexibility, it can be used in single phase, split-phase and "multi-phase" installations.

Because the WattsOn measures and accumulates all parameters individually on a per-phase basis, one meter can be used in multi-phase applications to measure and track each phase individually. Additionaly, total and net power/energy is computed automatically.

Some considerations:
1) The WattsOn is voltage independent provided that the line-to-neutral voltage of the system is within the input specifications (approximately 80V - 347V line-to-neutral).

2) All phases/circuits measured by any one meter must share a common neutral.

3) There are no settings required to configure the type of wiring system. However, some measurements are irrelevant depending on the type of system used.

Specifically, the line-to-line measurements performed by the WattsOn are calculated based on the assumption that the phase difference between voltages is 120 degrees (as in a three-phase system).

This assumption is incorrect for single/split phase systems. As a result these registers should simply be ignored.

Additionally, the "average" register calculations have no significance for single/split systems. The average registers are calculated as (A+B+C)/3. In single/split systems, this calculation will be incorrect because one or more of the phases may be disconnected and skew the calculation.

As a result, the "total" current or voltage may be calculated by the user's system, or bit 15 of the configuration word (40153) may be set to instruct the WattsOn to perform an addition only rather than average.

In this case, the "Average Voltage" register may be used to determine the line-to-line voltage of a split phase system, as the effective calculation will be changed to (A+B+C) where C=0.

Additional information can be found in the following Application Note:

AN0805 - Using WattsOn in Single Phase Applications