Technical Brief for Installation of Consumption Monitoring

Installing Consumption CTs
 2016 Enphase Energy Inc. All rights reserved. January 2016
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The terminals of the Envoy-S are rated for two #18 CT wires on a single terminal or one #14-#16 conductor.
Concerns around installing parallel consumption CTs:
• It is easy to make wiring errors
• It is critical to ensure that all of the conductors that pass through the line 1 CT terminate at circuit
breakers on the black/line 1.
• Line 2 conductors must pass through the line 2 CT.
• The parallel CTs may not be used to monitor more than 600A of current
• A fill calculation should be made to ensure that no more than 60% of the CT’s cross-sectional area is
filled with conductors.
• If the solar circuit is not passed through the consumption CTs, the Envoy-S consumption metering
setting must be set to Total rather than Net.
• As always, the safety standards spelled out in the National Electrical Code must be observed,
particularly in regard to multi-wire branch circuits.
Best practices for installing parallel CTs:
• If needed, rewire the service panel to make additional space for the consumption CTs
• Turn off the main breaker to reduce the risk of electrical shock. Remember to be cautious, as the line
side of the main breaker will remain energized when the main breaker is off.
• To simplify the rewiring, flag each conductor passing through the line 2 CT with red tape.
• Be careful to ensure that all red conductors are landed on line 2.
• Ensure that the ungrounded conductors of all multi-wire branch circuits are wired to line conductors
opposite from each other. This is critical because these circuits power 120V loads and use a shared
neutral.
• Always run multi-wire branch circuits to a common-trip, 2-pole breaker. The neutral wire (grounded
conductor) of a multi-wire branch circuit carries the unbalanced current of the two line conductors. If
the red and black conductors of the multi-wire branch circuit are tied to the same line, then the
neutral will carry the full current of both circuits and may result in damaged conductors and,
potentially, a fire.
• Use a tie wrap to hold the line conductors together prior to installing the CT around them.
Two #18 CT wires on
a single terminal