If a moderate percentage of non-permanent faults is present in a system, two or more shots are justified. If fused ‘tees’ are used and the fault level is low, the timer of the fuses may not discriminate with the main IDMT relay: several shots are usefull. This would not warm up the
fuse to a such extent that it would eventually blow before the main protection operated.
QO-HID and QOB-HID circuit breakers are for use in high intensity discharge (HID) lighting systems,
such as systems using mercury vapor, metal halide or high-pressure sodium lighting units. These
circuit breakers are designed to handle the high inductive loads, harmonic currents and cycling which
are inherent in HID lighting systems. QO-HID and QOB-HID circuit breakers are physically
interchangeable with standard QO circuit breakers and accommodate the complete range of QO
accessories.
QO-HID and QOB-HID circuit breakers are manufactured with larger contacts than standard QO and
QOB circuit breakers to allow switching of high inductive loads. They also have magnetic
characteristics similar to QO-HM and QOB-HM high-magnetic circuit breakers to allow the circuit
breaker to hold in against the high starting inrush currents which are typical in HID lighting systems.
QO and QOB Miniature Switches
Miniature switches are intended for use as disconnecting devices only. They provide no overcurrent
protection. QO and QOB switches are UL Certified for use on circuits capable of delivering not more
than 10 kA when protected by an equivalent rated circuit breaker or fuse. These switches are available
in 60 and 100 A rating.
QO and QOB switches are available with auxiliary switches only. (Shunt trip and bell alarm electrical
accessories are not available on QO and QOB miniature switches.) QO and QOB switches are
available with the complete range of handle accessories.
QOK and QOBK Key-Operated Circuit Breakers
Key-operated QOK and QOBK circuit breakers provide an alternative means for turning a circuit
breaker ON or OFF, as well as for resetting a tripped circuit breaker. The circuit breaker is turned on,
off or reset with a special key included with the circuit breaker. Key-operated circuit breakers are
available in one-pole construction only and can be mounted in any one-pole space which will accept a
standard QO circuit breaker. These circuit breakers are available in 10–30 A ratings, with interrupting
ratings of 10 kA at 120 Vac.
Replacement keys are available separately. Factory-installed or field-installable accessories are not
available on key-operated circuit breakers.
