Bus Bar (Opening) CT


The CTS series CTs are available with windows from 0.75 inch up to 2.0 inch. They have a removable section, so that they can be installed without interrupting the circuit.

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High Current Split-Core CTs

Bus bar style CTs are similar to split-core CTs, but are available in a wider range of window openings and current ratings. They have a removable section, so that they can be installed without interrupting the circuit.

  • Safe: burden resistor built-in, 333 mVac voltage output at rated full scale current, no shorting blocks needed
  • Current ratings from 100 to 6000 amps.
  • Accuracy ±1.5% from 10% to 130% of rated current
  • Phase angle <1.5 degrees
  • Lead wires 8 ft. long, 600 Vac rated, black and white, twisted-pair
  • UL recognized for voltages up to 600 Vac
  • Assembled in USA, qualified under the Buy American provision in the American Recovery and Reinvestment Act of 2009 (ARRA).
  • CTB Table of Dimensions
  • CTB Bus-Bar CT Datasheet (PDF)

Safety Note

Warning: Hazardous Voltages – Only qualified personnel or licensed electricians should install the WattNode meter and current transformers.

List prices (MSRP) for 1-30 piece quantities. Call for pricing on larger quantities.

Model Opening Rated Amps MSRP
CTB-1.5×3.5-0800 1.5″ x 3.5″ (38 mm x 89 mm) 800 $99.00 each
CTB-4.0×4.0-0800 4.0″ x 4.0″ (102 mm x 102 mm) 800 $99.00 each
CTB-4.0×4.0-1200 4.0″ x 4.0″ (102 mm x 102 mm) 1200 $109.00 each
CTB-4.0×4.0-2000 4.0″ x 4.0″ (102 mm x 102 mm) 2000 $116.00 each
CTB-4.0×4.5-3000 4.0″ x 4.5″ (102 mm x 114 mm) 3000 $125.00 each
Custom Models
Opening Widths from 1.0″ to 12.0″ (25 mm to 305 mm)
Leg Lengths from 2.5″ to 24.0″ (64 mm to 610 mm)
100 to
6000 amps


Bus-bar style CTs measure high currents in multiple parallel conductors and bus bars. They are typically installed where the multiple conductors making up one phase connect together at the end of a bus-bar, or at the lugs of a breaker or disconnect. Space is typically limited at these locations which makes selecting a window opening size difficult. We only stock five popular sizes but hundreds of different lengths, widths, and current ratings are available on a custom order basis.

Below are full scale drawings of the bus-bar CTs that we stock. These can be download, printed out, and glued to a piece of cardboard. Cut around the perimeter and then cutout the window opening and the removable section. Use as a gauge to help determine if the CT will fit. Keep in mind that these CTs are about 1.25 inches thick and should be spaced at least an inch apart.

To order custom opening sizes and current ranges of CTB Series CTs, replace the ‘W’ in the Custom Model part number with the opening width in inches and the ‘L’ with the leg length in inches, and the ‘Amps’ with the full scale current rating required. Note: Custom CTB Series CTs are non-cancelable and non-returnable (NC/NR) items with typical lead times of 3 to 4 weeks.