Introduction
General
Information
QOB (bolt-on) one-, two- and three-pole thermal-magnetic
circuit breakers provide overcurrent protection and
switching on ac and dc systems. Bolt-on QOB circuit
breakers are for use in NQO and NQOD panelboards.
Operating
mechanism
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
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.
Construction
Standards
QOB circuit breakers are built to comply with UL Standard
489, CSA 22.2 No. 5, NOM/ANCE and NEMA Standard AB1
and to meet Federal Specification W-C-375B/GEN.