Tools and Materials Needed
- Three-phase kWh sub-meter (compatible with your voltage and current requirements).
- Current Transformers (CTs) rated for your system.
- Electrical panel and necessary breakers.
- Screwdrivers and pliers.
- Wire stripper and cutter.
- Voltage-rated wiring.
- Insulation tape and cable ties.
- Personal Protective Equipment (PPE) (gloves, goggles, etc.).
- Multimeter for verification.
- Installation manual for your specific sub-meter model.
Submeter Installation Steps
Preparation
- Turn off the main power supply to the panel where the sub-meter will be installed.
- Ensure you are familiar with the electrical schematic and wiring diagrams for your sub-meter and CTs.
- Confirm that your sub-meter and CTs are rated for the correct voltage and current for your system.
- Always check the manufacturer’s sub meter installation diagram before starting the installation to confirm the correct CT orientation, terminal connections and wiring arrangement for the specific meter.
Mount the kWh Sub-Meter
- Locate a suitable spot on or near the electrical panel.
- Secure the sub-meter with screws or DIN rail mounts, as required.
Install the Current Transformers (CTs)
- Identify the three-phase conductors (L1, L2, L3) in your panel.
- Place each CT around the corresponding conductor. Ensure the orientation follows the marked arrow (often labelled “Load” or “P1”) to point toward the load.
- Tighten the CT around the conductor securely.
Sub Meter Installation Diagram & CT Wiring
- Connect the secondary wires from each CT to the corresponding input terminals on the sub-meter (e.g., CT1 to L1, CT2 to L2, CT3 to L3).
- Use the colour codes or labels provided in the installation manual for correct polarity (S1 and S2 terminals).
Connect the Voltage Inputs
- Connect the phase wires (L1, L2, L3) and neutral wire to the voltage input terminals on the sub-meter.
- Use appropriate fuses or breakers for protection as recommended in the sub-meter manual.
Verify Connections - Double-check all connections:
- Correct CT to phase matching (CT1 to L1, CT2 to L2, CT3 to L3).
- Voltage connections are properly aligned to the respective input terminals.
Power Up and Test
- Turn the power back on.
- Use a multimeter to verify that the voltage inputs to the sub-meter are correct.
- Check that the sub-meter powers on and displays correctly.
- If your sub-meter requires programming for CT ratios or system configuration, follow the manual to input these settings.
Secure Wiring - Bundle and secure loose wires with cable ties.
- Ensure all connections are insulated and safe from accidental contact.
Verify Functionality - Confirm that the sub-meter is correctly measuring the voltage, current, and energy usage for all three phases.
- Compare readings with a known load or reference meter to ensure accuracy.
Tips for Safe Installation - If you are not experienced with electrical systems, hire a licensed electrician to perform the installation.
- Adhere to local electrical codes and regulations.