Power Distribution

Square D Safety Switches
QO Load Centers
QO and QOB Circuit Breakers
MULTI 9 Miniature Circuit Breakers
MASTERPACT Circuit Breakers
Circuit Breakers Enclosures
NQ Panelboard
NF Panelboard
Switchboard / Switchgear
General Purpose Dry Type Transformers
I Line Panelboard
Intelligent Load centers
Powerpact H & J Circuit Breakers
Square D Industrial Control Transformers

QO® (plug-on) and QOB (bolt-on) one-, two- and three-pole thermal-magnetic circuit breakers provide overcurrent protection and switching on ac and dc systems. Plug-on QO circuit breakers are for use in QO load centers, NQ and NQOD panelboards, OEM mounting bases, and Speed-D® switchboard distribution panels. Bolt-on QOB circuit breakers are for use in NQO and NQOD panelboards.

Operating mechanism

QO and QOB circuit breakers have an overcenter, trip-free toggle mechanism with quick-make, quickbreak action and positive handle indication. The tripping mechanisms in two-and three-pole circuit breakers operate such that an overcurrent on any pole of the circuit breaker will cause all poles of the circuit breaker to open simultaneously. Each pole has an individual thermal-magnetic trip element calibrated for 40°C ambient temperature.

Trip Indication

QO and QOB circuit breakers have Visi-Trip® trip indication, which provides a visual indication that the circuit breaker has tripped and interrupted the circuit. When the circuit breaker has tripped, the handle assumes a center position and the red Visi-Trip indicator appears in a window in the circuit breaker case. The Visi-Trip indicator is only visible when the circuit breaker has tripped. Trip indication immediately distinguishes the circuit from any other circuit which is merely in the on or off position. The circuit breaker can be reset by pushing the handle to OFF and then to ON.

The industry leader in circuit protection is easily recognized by the industry's only trip indicator—the red Visi-Trip® Indicator makes it easy to spot a tripped circuit breaker. Compact 3/4 in. wide format for one-pole circuit breakers helps minimize panel space and footprint. The Square D® exclusive Qwik-Open® protection is standard on all 15 A and 20 A circuit breakers— trip reaction within 1/60th of a second. No other circuit breaker trips faster. A comprehensive selection of 10kA rated circuit breakers is available including:

• QO® one-pole standard circuit breakers (10 A to 70 A)
• QO two-pole standard circuit breakers (10 A to 200A)
• QO three-pole standard circuit breakers (10 A to 100 A)
• QO tandem circuit breakers (15 A to 20 A)
• QO ground-fault circuit interrupters (1- and 2-pole, 15 A to 60 A; 3-pole 15 A - 50 A)
• QO-EPD circuit breakers with 30 mA equipment ground-fault protection (1-pole, 2-pole, 15 A to 60 A; 3-pole, 15 A - 50 A)
• Square D arc-fault circuit interrupters (1-pole, 15 A and 20 A)
• Square D combination arc-fault circuit interrupters (1-pole, 15 A and 20 A)
• QO-K circuit breakers, key operated (1-pole, 10 A to 30A)
• QO-SWN circuit breakers with switch neutral common trip, NEC 514-5 (2- and 3-pole, 10 A to 50 A)
• QO-HID circuit breakers for circuits feeding fluorescent or high intensity discharge (1-, 2-, and 3-pole, 15 A to 50 A)
• A full line of factory installed accessories, such as shunt trips, auxiliary switches and alarm switches, is also available.
• QO sub-feed lugs, 2-pole rated 60A, 125A and 225A; 3-pole rated 125A.
• Additional products available with interrupting ratings of 22kA, 42kA and 65kA.

Plug-on QO circuit breakers are for use in QO load centers, NQ panelboards or Speed-D switchboard distribution panels. Bolt-on QOB circuit breakers are for use in NQOD panelboards.