Overview
The most common installation issue with retrofit energy metering is known as a phase mismatch, which will cause incorrect power calculations and often lower-than-expected power factor. In addition, the power readings may be the opposite of expected polarity (based on CT orientation).
It's extremely important to verify correct phase-matching between CTs and associated line voltages when making power calculations using a retrofitted energy meter. Follow the steps in this article to verify correct phase matching between CTs and Line Voltages.
Prerequisites
Electrocution hazard!
This procedure should only be attempted by a certified electrician. All proper safety precautions should be taken when completing this process.
- A Voltmeter is necessary to complete these steps.
Instructions
Step 1: Using a handheld voltmeter set for the voltage of the system, place one probe on the L1 voltage terminal of the eGauge AC Mains connector and the other probe to the conductor the CT is around.
Step 2: Check the Voltage reading between the two points. A reading of 0 VAC means they're on the same phase, while a reading of 208 VAC (or expected phase-to-phase voltage) means they're on different phases and the conductor the CT is around is not landed on L1. Check the monitored conductor against L2 and L3 (if present) and look for a 0 V reading.
Step 3: For each installed CT repeat the steps above and record the CT + Line Voltage pairs where a 0 VAC reading is noted for use in the configuration portion of the setup.
Troubleshooting and Tips
-
Issue: I've verified that my phasing is correct but my readings still don't look right.
- Solution: Ensure that the CT is fully closed, and that there are no bad splices if the CT lead has been extended. Readings should be verified when there is sufficient current flowing through the CT.