Issue
A user would like to total multiple loads with an Energy meter.

Product Line
Powerlogic Energy Meter

Environment
Energy Meter Installation

Cause
The installation guide for the Energy meter does not contain instructions on wiring the meter to monitor multiple loads.

Resolution
*Warning: Installation and maintenance of this device should only be performed by qualified, competent personnel that have appropriate training and experience with high voltage and current devices. Failure to follow the instructions / warnings in the Meter Installation Guide can result in permanent damage to the meter, severe injury or death.

The Energy meter is calibrated with the set of CTs that are included with the meter, however the Energy Meter can be installed with up to three sets of parallel CTs to monitor multiple loads. When wiring multiple current transformers in parallel to the Energy Meter, all voltages corresponding to the individual loads must be the same voltage values and must be from the same source. The voltage applied to the inputs of the Energy Meter will be used in the power calculations. Monitoring different voltage values and monitoring the same voltage values from different sources will both cause the power calculations to be inaccurate.

For example, if load A has a system voltage type of 120/208 VAC, and load B has a system voltage type of 277/480 VAC, an Energy Meter cannot be used to measure both loads in a parallel configuration. Likewise, if Load A and Load B both have a system voltage type of 120/208 VAC, but are supplied their respective voltage from different transformers, an Energy Meter cannot be used to measure both loads in a parallel configuration.

Note: When multiple sets of CTs are connected in parallel to the Energy Meter, the accuracy drops from less than 1% to between 1%-3%.

Please follow the guidelines in the attached addendum for selecting and installing the parallel CTs on an Energy meter.