3-phase 3-wire systems have 3 hot wires and NO neutral wire. These are generally older 3-phase systems. You will need 1 Omnimeter and only 2 CTs for this kind of a system. Metering of these systems can be done with any of our EKM Omnimeter models. However, for metering 3-phase 3-wire systems above 415VAC you will need to use the Omnimeter HV v.5, which is capable of metering such systems up to 600VAC.
If you are wondering why you only need 2 CTs for a 3-phase system you can consult Blondel's Theorem
The images and diagrams shown here are in no way exhaustive. These are just a few examples of how you might set up a metering system, and are simply intend to show what is possible. These are the options that you might consider for your metering setup:
- Do I want to read the meter(s) locally with computer or do I want a cloud based solution (EKM Push).
- What diameter and amperage rating will I need for the Current Transformers? You will need two CTs for your 3-phase 3-wire electrical system.
- Do I need to go wireless?
- Do I have a need to daisy chain multiple Omnimeters together? This allows you to connect multiple Omnimeters in series, which can then be connected to a single communication device.
The answers to these questions should help you narrow down your options and allow you to select the products that you will need for your particular application.
For a 3-phase 3-wire system you will need to use 2 CTs. You will have 3 hot wires and NO neutral wire.
- Turn off power to the subpanel.
- Mark one of the hot wires as L1, mark the second wire as L2, and mark the last hot line as L3. You can pick these randomly.
- First, install a jumper wire from port 8 on the Omnimeter to port 10 on the Omnimeter. Connect the L1 hot line voltage reference wire to port 7 on the Omnimeter, connect the L2 hot line voltage reference wire to port 8 on the Omnimeter and connect the L3 hot line voltage reference wire to port 9 on the Omnimeter.
- Connect the CT1 so that the L1 hot wire passes though it and the arrow on the CT points towards the load. Connect the CT3 so that the L3 hot wire passes though it and the arrow on the CT points towards the load.
- Connect the CT1 black wire will go to port 1 on the Omnimeter and the CT1 white wire will go to port 2 on the Omnimeter. Connect the CT3 black wire will go to port 5 on the Omnimeter and the CT2 white wire will go to port 6 on the Omnimeter.
When this meter is properly connected it will read volts and current on L1 and L3, but will read 0 volts and current on L2.
This video tutorial provides an example of how to install an Omnimeter Pulse v.4 on a 120/240v electrical system. You can use this video to infer how a three phase, three wire installation might go. For this type of electrical system the CT and voltage reference wiring will be different so refer to the diagram above for that information:
See this model for reference of how to properly connect an Omnimeter to a 3-phase 3-wire system: