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The CT is the hybrid system’s eyes on the grid connection. Every smart function — self-use, export limiting, and the energy figures on the display — is only as accurate as the clamp on that one conductor. Get this right and the system controls correctly; get it wrong and the symptoms can look like an inverter fault.
For trained and authorised installers only. Isolate the AC conductor before clamping anything around it.

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What the CT is for

A current transformer (CT) clips around a grid conductor and reports the current flowing through it. The inverter uses that signal to determine whether the site is importing or exporting, and by how much. That information drives:
  • Self-use logic — directing PV and battery to cover the load before buying from the grid
  • Zero-export control — throttling PV output when the site would otherwise export
  • Energy display figures — grid import, export, and load values on the screen and the app
Without a healthy CT signal, none of these functions work correctly. The system has no reliable way to know what is happening at the meter.

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The clamp rule

  • The CT clamps around one conductor: the live. Clamping around the live and neutral together cancels the magnetic fields — the CT reads 0 W and the control logic goes completely blind.
  • Close the clamp until it clicks fully shut. A half-latched CT under-reads consistently and the fault is nearly invisible until someone moves the cable.
  • Where the CT sits and which way its arrow faces are separate disciplines — both are covered on Direction & Location.

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Ratio discipline

The CT reports a scaled-down version of the conductor current. The ratio setting tells the inverter the scale factor. A wrong ratio means every power figure on the display is wrong by a large factor — and export limits are enforced against numbers that have nothing to do with the actual grid flow.
Pending Kent validation. [KNB-VAL-08] The shipped CT scheme and ratio per Kent SKU are under confirmation. Until published here: read the ratio from the shipped CT’s nameplate and enter exactly that value — never assume a default. On the Kent G3, the box-kit CT and the meter-scheme CT carry different ratios; the kit table is on the Kent G3 CT & Meter page.

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Lead length — the quiet killer

The CT’s output is a millivolt-class analog signal. Long or improvised lead extensions pick up electrical noise, and that noise reads as phantom import or export that the control loop continuously chases.
  • The Kent G3 box kit ships with a 1 m, 2.3 mm² CT lead — that is the design lead length for that kit.
Pending Kent validation. [KNB-VAL-23] The approved CT lead extension method per Kent SKU is under confirmation. Until published here: do not extend CT leads. If the supplied lead cannot reach the grid connection point, use the platform’s meter scheme instead — never a spliced-on length of flex.

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CT scheme vs meter scheme

Both Kent platforms can sense the grid either directly with CTs on the conductor, or through a supported energy meter that carries its own CTs and communicates over RS485 to the inverter. You choose one scheme per site — not both.
On the Kent G3, if CTs are connected directly, a separate smart meter is not required for grid sensing. The platform-specific wiring options are on the Kent M1 CT & Meter and Kent G3 CT & Meter pages.

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Common mistakes

The magnetic fields cancel. Load reads 0 W and all control logic is blind. Reclamp on the live conductor only.
Ratios vary by CT model and SKU. Always read it off the physical CT you installed.
Even a short extension on an analog millivolt signal introduces noise. Use the meter scheme if the lead cannot reach.
The CT under-reads until disturbed. Always confirm the click before closing up the enclosure.