Installing ZEM current transformers

The Zem is EpiSensor's accurate, wireless three-phase electricity monitor. It ships with its current transformers pre-wired and calibrated: one clips around each phase conductor, so nothing has to be cut or rewired to fit them. It's double insulated and sealed to IP sixty-seven, so it can go inside or outside an electrical panel, even somewhere dusty or dirty, without a separate enclosure. Fitting them is work for a qualified electrician.

Switch off every supply that feeds the panel, including any backfeed, prove it's safe with a properly rated voltage tester, and wear the right protective equipment. For conductors up to fourteen millimetres in diameter, the Zem uses split-core CTs, rated to a hundred and twenty amps per phase. For larger cables, it uses flexible Rogowski coils: three hundred amps, for cables up to about seventy millimetres in diameter, or a thousand or three thousand amps, up to a hundred and twenty.

To fit a split-core CT, open it, clip it around the conductor with its arrow pointing the way the current flows, and close it until it clicks: the click means the core is fully seated. Then check it's held firmly, and can't slip. A Rogowski coil wraps around the conductor, and clips shut at its end. Keep the conductor roughly centred in the loop, and mind the direction arrow here too.

Each current transformer is labelled for its phase, and goes on the same phase as the matching voltage reference input, so power is measured phase by phase. The current transformers are calibrated with their Zem, for system-level accuracy of Class zero point five S. So keep the set together: don't extend or shorten the cables, and don't swap them between inputs. Before you close up, check the arrows follow the current, each sensor sits on its own phase, every core has clicked shut, and nothing can slip.

Get those right, and the Zem reports accurate energy straight into Edge: total kilowatt-hours, and the energy used in each fifteen-minute interval, ready for charts, alerts, automation and dashboards, from the first reading. ZEM current transformers. The full installation instructions are at EpiSensor dot com, forward slash documentation.