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AC split-core CTs measures the amperage of a conductor on an AC (alternating current) system. Combined with voltage measurements, this allows calculation of power and energy values. AC CTs provided by eGauge are split-core, meaning they can be wrapped around a conductor instead of having to disconnect the conductor and feed it through the CT.

eGauge supports a variety of  split core CTs that are available with standard 1% accuracy or 0.5% accuracy for revenue grade applications. Visit our webstore for more details.

Follow the steps in this article to properly install split-core CTs for your eGauge. 

Prerequisites

• Before beginning be sure to read all documentation and/or inserts that were included with your CTs.
• CTs purchased from eGauge will be compatible with your meter. If you purchased CTs from another source, check that they are compatible by reading our FAQ topic on CT compatibility.
• Supported CTs not purchased from eGauge Systems may not come equipped with 2-pin CT plugs. If needed, they can be purchased from our web store.

Instructions

Step 1: Open the CT by gently releasing the latch and then opening the CT wide enough to position over the conductor to be monitored. Do not touch the core surface inside where the CT opens. Any oils or debris in that area worsens accuracy.

Step 2: Slide the CT over the conductor of the circuit to be measured. 

Step 3: Close the CT by engaging the latch. Verify that the CT is fully closed by firmly squeezing together the top and bottom parts of the CT.

When a CT is not fully closed the clip will not lay flush against the CT:

When a CT is fully closed the two halves of the split-core CT will make good contact and the clip should lay flat against the side of the CT as shown:

Step 4:  If the CT fits so tightly around the conductor that it needs to be forced close, the CTs should be replaced with a CT with a larger opening. The CT should fit easily around the monitored conductor.

Step 5: Secure the CT to the conductor with a cable tie (optional).

Step 6: Route the twisted pair wires of the CT to the meter such that they do not directly contact live terminals or bus bars.

Step 7: Plug the 2-pin terminal at the end of the twisted pair wires into an unused port on the meter lining up the black and white leads with port markings as shown below:

Step 8: Using a handheld volt meter, verify CT phasing by taking a voltage reading between the monitored conductor and the eGauge AC Voltage ports. Check L1, L2 and L3 and make a note of the CT port used and the voltage port where you see a 0 VAC reading between points as shown in the graphic below.

Step 9: Record the eGauge sensor port used, CT model and Amp rating as well as the monitored load and phase verified in the previous step for reference. This information will be needed later for proper meter configuration. Use the Installation information pages in the back of the manual or create your own spreadsheet to record this information.

Example:

Extending AC CT Leads

If AC CT leads must be extended, please follow these guidelines:

• 18 ga. twisted pair wiring, or Cat 5 cable (1 twisted pair per CT) is recommended.
• Splices should be soldered or completed using appropriate connectors such as the eGaugeCT Extension Pack. Wire nuts should not be used.
• Extensions recommended not to exceed a maximum of 100 feet.
• Avoid running alongside any high voltage wiring to reduce the potential for interference.

Troubleshooting and Tips

• Tip:  CT orientation direction matters, be sure to orient CTs consistently. Direction will affect polarity.
• Tip: If CTs do not close easily and need to be forced onto the conductors, they should be replaced with a larger CT.  CTs that are too tight will not read correctly.

Additional Resources