Wiring guidelines for Three Phase CT and Direct Connect meters

Installers should pay careful attention to the physical and electrical orientation of current transformers when installing three phase meters that measure energy indirectly via CTs. Such as the Elster A1140-CT and Iskraemeco MT375-CT which can be purchased from our store.

Wiring Guidelines for 3 Phase Current Transformer Meters

Follow the wiring diagram inside the terminal cover

Voltage inputs to the meter must be externally fused

CTs must match the CT ratio programmed to the meter

Meters can be remotely re-programmed to a different CT ratio if the current rating of the clamp is changed.

CT clamps must all be fitted to the cables the same way round

There is normally a P1 and P2 label on either side of the CT, or an arrow pointing from P1 to P2.  For standard consumption metering or for export meters, P1 should be on the mains side with the arrow pointing towards the source of the load.

The cable leads must be wired the same way around

Reversed cabling or cross wired CTs will give a false reading on the meter.  The electrical orientation should be consistent across the 3 phases.

The CT clamps must be on the correct phase for the voltage reference

The voltage reference terminals are between each of the CT terminals for each phase.

Finally, always check the meter instant power values on the display

Using the information on the meter display, confirm that the import and export readings are increasing as you would expect.  Also check the instant power values to prove there are no reversed or missing phase power values.  The red kWh LED should flash for every Watt that flows through the meter.

Split core current transformer open
Elster A1140 Smart Meter
Three Phase Direct Connect Meters

Wire the meter according to the wiring diagram in the terminal cover

Direct connect meters must not exceed 100A on any phase

Check that the power values are correct on the meter display

The red LED on the meter should flash indicating there is energy flow through the meter