The Vue energy monitor uses Current Transformer (CT) sensors to measure the current flowing through each circuit line. This article covers how to correctly place, orient, and configure your sensors — including special cases for 200A mains sensors, multi-pole circuits, and multiplier settings.

200A CT sensors are included in all Vue packages. They connect to the three main ports (labeled A, B, C) on the Vue gateway and monitor whole-home energy usage from your main service lines. The number included depends on your system type — split-phase packages include 2 and three-phase packages include 3.

50A CT sensors are included in the 8-Sensor and 16-Sensor bundles only — they are not included in the Monitor Only package. They connect to the numbered side ports and monitor individual branch circuits such as HVAC systems, EV chargers, dryers, water heaters, and other appliances. Additional 50A sensors can be purchased individually or in packs of 8 from the Emporia shop at any time to expand up to 16 circuits total.

Sensor current limits. 50A side sensors on Vue Gen 2 and Gen 3 can handle up to 75A through the clamp before mechanical saturation begins (full accuracy through 63A — see CT Accuracy: What to Expect from Your Measurements). On the older Vue Gen 1, the side sensors are rated to 50A maximum. For circuits that may exceed these limits, use a 200A CT with a multiplier (covered below) or contact Customer Support for guidance.

Flexible Sensors (Rogowski coils) are available separately and are required for certain panel types where standard 200A clamp sensors cannot fit. This includes panels with metal bus bars instead of individual wire connections, and combination panels with four main lines. Flexible Sensors are not included in any standard kit. If you are unsure whether your panel requires them, send a photo to our Customer Support team before ordering, or visit the Emporia shop to purchase.

CT sensors do not need to be placed at the breaker itself. They can be positioned anywhere along the circuit line — at the breaker end, midway along the wire, or closer to the load. This flexibility is useful when panel space near the breaker is tight. Sensors must only be placed on live (hot) wires. Do not place a sensor on a neutral wire.

Each CT sensor has a directional arrow labeled "Breaker" on the body of the clamp. This arrow should always point toward the breaker — away from the load or appliance — on every circuit, including solar and generation circuits.

For solar and generation circuits, current direction is handled in the app through the Bi-Directional circuit setting rather than by physically reversing the sensor. When enabled, the app will prompt you to confirm whether the circuit is currently consuming or generating to establish the correct direction. See the Solar Monitoring article for full setup details.

The Vue Gen 3 automatically identifies the phase and voltage on each port — you do not need to match a specific sensor to a specific port number.

Terminal block sizes

The 200A and 50A sensors use different terminal block sizes — 50A sensors use a 3.81mm terminal block and 200A sensors use a 5.0mm terminal block. This means sensors cannot be swapped between port types without first re-terminating the sensor wires into the correct terminal block size.

Can a 200A sensor be used in a side port?

Yes. To use a 200A CT sensor in a side port, re-terminate the sensor wires from the 5.0mm terminal block into a 3.81mm terminal block to fit the side port. When re-terminating, match the black wire (positive) to the solid-marked terminal and the white wire (negative) to the empty-marked terminal. Once connected, set a multiplier of 4.0 on that circuit in the app to correct for the calibration difference between sensor sizes.

Can I use a 50A CT sensor in a main port (A, B, or C)?

Yes. To use a 50A CT sensor in a main port, re-terminate the sensor wires from the 3.81mm terminal block into a 5.0mm terminal block for compatibility with the main port. Once connected, set a multiplier of 0.25 on that circuit in the app settings to correct for the calibration difference between sensor sizes.

Important: Any sensor connected to the ABC main ports — regardless of what it is clamped around — will be counted as Total Usage in the app. If you connect a 200A sensor to a main port but clamp it on a branch circuit rather than the mains, the app will treat that branch circuit reading as your whole-home total, which will cause incorrect Balance and usage calculations across all other circuits.

As a general rule, each CT sensor should encircle only one wire. This provides the most accurate measurement for that circuit.

Exception — multiple same-phase lines through one sensor: It is acceptable to run more than one wire through a single sensor, provided all wires are from the same phase of power. In this configuration, the sensor measures the combined total current from all lines inside the clamp and displays it as a single reading in the app.

Never mix phases through a single sensor. Placing wires from Phase A (L1) and Phase B (L2) together inside one sensor causes the two currents to partially cancel each other, resulting in significantly understated readings. This is a common installation mistake in split-phase panels where breakers alternate phases down each column.

Do the 200A CT sensors need to be connected?

No. The 50A sensors on branch circuits operate independently and do not require the 200A sensors to function. If you only want to monitor individual circuits and are not interested in whole-home totals, you can leave the 200A sensors disconnected.

When the 200A sensors are not connected, the app adjusts automatically:

If space in your panel makes installing standard 200A clamp sensors difficult, Flexible Sensors are designed for tight spaces and can monitor your main service cables from a different position. Note that the small Flexible Sensor power unit also requires panel space.

Can the 200A sensors be used to monitor a branch circuit?

Yes. 200A CT sensors can accurately monitor branch circuits and sub-panels, including 30A circuits. To do this, re-terminate the sensor wires from the 5.0mm terminal block into a 3.81mm terminal block and connect it to any available side port. Set a multiplier of 4.0 on that circuit in the app settings to account for the calibration difference. See the Port Assignments section above for full wiring details.

Flexible Sensors install differently from rigid 200A or 50A CTs. They're Rogowski coils paired with active integrators, and they need their own power supply. The full step-by-step install reference is the Flexible Current Sensors Installation Guide at emporiaenergy.com/product-documentation. This section covers the points specific to flex sensors that differ from rigid CT install.

What ships in the kit

Critical: coil orientation. Each Rogowski coil has a directional label on the body. The label must point AWAY from the breakers — the white label faces the service entrance side of the panel. Installing with the label in the wrong orientation inverts your readings (the same effect as a rigid CT installed backwards). Confirm orientation before closing the coil clasp.

Step-by-step

Video walkthrough

Wiring scenarios for the flex sensor power supply. The flex sensor power supply needs its own breaker landing in addition to the Vue's wire harness. The right wiring depends on (a) how many empty breakers you have, and (b) how many main CTs you've installed. The four scenarios in the install guide are:

For the exact wiring diagram for your scenario, see Steps 7a–7d in the Flexible Current Sensors Installation Guide.

Flexible Sensor specifications

Dual-pole and multi-pole breakers supply 240V to large appliances like electric water heaters, dryers, air conditioners, EV chargers, and electric ranges. These circuits have two hot legs rather than one, which creates a monitoring decision: use one sensor or two.

Option 1 — Two sensors (one per leg): This is the most accurate approach. Place one 50A CT sensor on each hot leg of the circuit. No multiplier is needed. The two sensors can be merged into a single combined reading using the Circuit Merging feature in the app (Settings → Manage Devices → select circuit → Merge). This is recommended for sub-panels, appliances with a neutral wire return (dryers, ranges, ovens), and any circuit where load may be unbalanced between the two legs.

Option 2 — One sensor with a multiplier of 2.0: Place a single 50A CT sensor on one leg of the circuit and set a multiplier of 2.0 in circuit settings. This conserves a sensor port and works well for balanced 240V loads with no neutral return — such as electric water heaters, baseboard heaters, air conditioners, EV chargers, and similar resistive or motor loads. It is not suitable for appliances with both 240V heating elements and 120V control components (like dryers or ranges), as those loads can be unbalanced and the multiplier will overstate or understate actual usage.

For single-phase systems and any single-pole breaker, the default multiplier of 1.0 is correct in all cases — no changes are needed.

Vue Gen 1 mains. Older Vue Gen 1 devices still require a 2.0 multiplier on the mains for 240V split-phase systems. The Gen 2 and Gen 3 measure voltage directly and adjust automatically — do not apply a mains multiplier on those generations.

To set or adjust a multiplier for a circuit:

For all standard single-pole circuits, leave the multiplier at the default value of 1.00.

This knowledge base is continuously updated to provide the most helpful guidance for Emporia customers. If you found this article unclear or have suggestions for improvement, please contact our Customer Support team.