CTBL Large Split-Core CT


The CTBL Series of current transformers (CTs) are stocked in five rated currents from 800 A to 3000 A. Custom models are available with current ratings up to 6000 A and window openings up to 8 in by 24 in.

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Large Opening High Current Split-Core CTs

The CTBL Series of CTs are similar to split-core CTs, but are available with higher rated currents and larger window openings. Commonly called bus-bar CTs, they are typical installed on parallel phase conductors. They have a removable section, so that they can be installed without interrupting the electrical service.

  • Safe: burden resistor built-in, 0.333 Vac (333 mVac) voltage output at rated full scale current, no shorting blocks needed!
  • Accuracy ±1.5% from 10% to 100% of rated current
  • Phase angle 0.0 to 1.5 degrees leading from 20% to 100% of rated current
  • UL Listed 2808 (XOBA) for field installation in panels up to 600 Vac
  • Current ratings from 800 to 6000 amps.
  • Lead wires 8 ft. long, #18 AWG black and white, twisted-pair, MTW, UL 1015 600 Vac ,
  • Assembled in USA, qualified under the Buy American provision in the American Recovery and Reinvestment Act of 2009 (ARRA).

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



  • Model CTB Bus Bar Current Transformer Dimensions Table, inches (millimeters)
Bus Bar Current Transformer Dimensions Table
CTBL-1.5×3.5-08003.5 (89)1.5 (38)5.47 (139)3.74 (95)1.08 (27.5)
CTBL-4.0×4.0-08004.0 (102)4.0 (102)6.22 (158)6.61 (168)1.15 (29.0)
CTBL-4.0×4.0-12004.0 (102)4.0 (102)6.22 (158)6.61 (168)1.15 (29.0)
CTBL-4.0×4.0-20004.0 (102)4.0 (102)6.22 (158)6.61 (168)1.15 (29.0)
CTBL-4.0×4.5-30004.5 (114)4.0 (102)6.72 (171)6.61 (168)1.15 (29.0)

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. Custom CTs are non cancelable non returnable (NC/NR) items.

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.

Models & Pricing

List prices (MSRP) for 1-30 piece quantities. Call for pricing on larger quantities.  Custom CTs are non-cancelable non-returnable (NC/NR) items.

ModelOpeningRated AmpsMSRP
CTBL-1.5×3.5-08001.5″ x 3.5″ (38 mm x 89 mm)800$130.00 each
CTBL-4.0×4.0-08004.0″ x 4.0″ (102 mm x 102 mm)800$140.40 each
CTBL-4.0×4.0-12004.0″ x 4.0″ (102 mm x 102 mm)1200$150.80 each
CTBL-4.0×4.0-20004.0″ x 4.0″ (102 mm x 102 mm)2000$161.20 each
CTBL-4.0×4.5-30004.0″ x 4.5″ (102 mm x 114 mm)3000$176.80 each
Custom Models
Opening Widths from 1.5″ to 12.0″ (38 mm to 305 mm)
Leg Lengths from 2.0″ to 12.0″ (51 mm to 305 mm)
100 to
6000 amps


CTBL – Downloads

Brochure, Datasheet, Manual, and Application Notes

  • Manual & Installation Instructions


CTBL – Options

Custom Sizes

  • Custom Part number: (CTBL-WxL-Amps)
  • Replace the ‘W’ in inchs for inside opening width
  • Replace the ‘L’ in inchs for the inside leg length
  • Replace ‘Amps’ with full scale rated current
  • Typical lead times of 3 to 4 weeks
  • Custom CTBL’s are non-cancellable and non-returnable (NC/NR)