Circuit total limitation

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Circuit total limitation (CTL) is one of the present-day standards for electrical panels sold in the United States according to the National Electrical Code. The 1965 edition of the NEC, article 384-15 was the first reference to the circuit total limitation of panelboards.[1] As of 2008, the location of this language is at Article 408.54. Non-CTL panels have not been made by reputable manufacturers since 1965.[citation needed]

Non-CTL replacement only[edit]

Circuitboards and panelboards built prior to 1965 do not have circuit total limiting devices or features built-in. Even so, pre-CTL circuit breakers "for replacement use only"[2] are still sold in local hardware stores. As a result, numerous unsafe situations have resulted where panels were dangerously overloaded because these non-CTL breakers continue to be used.[citation needed] With overuse of non-CTL breakers, current is being placed on the panel's bus-bars in excess of the designed capacity of that panel.

The 2008 code did away with the previous 42 circuit limitation on panelboards.[3] One can now order panelboards with as many as 84 circuit places, and a corresponding ampacity rating. If a panelboard with a sufficient number of breaker positions is installed in the first place, the need for non-CTL breakers should be eliminated.

Gallery[edit]

See also[edit]

References[edit]

  1. ^ Terrell Croft, Wilford I. Summers, Frederic Hartwell. "American Electricians' Handbook". 15th Edition. p. 4.52. 
  2. ^ "UL's Guide Information for Electrical Equipment: The White Book 2008" (PDF). p. 90. 
  3. ^ See "bullet" in 2008 NEC between Articles 408.30 and 408.36, where 2005's Article 408.35 appeared.

External links[edit]