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Miniature circuit breaker application
FAZ circuit breakers
PRODUCT OVERVIEW
EATON CORPORATION UL 489 and UL 1077 DIN Rail Miniature Circuit Breakers
Supplementary protectors
As mentioned, the standard FAZ line fulfills all of the criteria
per code of “supplementary overcurrent protective devices,”
or “supplementary protectors,” as they are better known.
What is the definition of a supplementary protector
per North American standards?
A supplementary protector is a manual reset device designed
to open the circuit automatically on a predetermined value
of time versus current or voltage within an appliance or other
electrical equipment. It may also be provided with manual
means for opening or closing the circuit. (Source: UL 1077)
In the United States (and similarly in Canada) the NEC 2005
further defines supplementary protectors as devices intended
to provide limited overcurrent protection for specific applications,
such as lighting fixtures and appliances. This limited protection
is in addition to the protection provided in the required branch
circuit by the branch circuit overcurrent protective device.
Clearly, the underlying message in those definitions is that
supplementary protectors are not branch circuit overcurrent
protective devices per code, and neither are they tested that
way per UL and CSA standards. They cannot replace the primary
protective role performed by listed and certified molded case
circuit breakers and fuses.
That explains, in part, their status by UL as “recognized only”
devices. Supplementary protectors will never bear a UL listing
mark, simply because their suitability as protective devices is
dependent on a number of acceptability conditions that can
vary from make to make and ultimately define the manner in
which they can be properly applied per code. The manufacturer
should be consulted in all cases when evaluating the suitability
of “recognized only” components such as UL 1077
supplementary protectors.
FAZ protectors are not subject to any specific restrictions in this
respect, other than, like all supplementary protectors, they must
never be used as a substitute for true listed and certified primary
overcurrent protective devices.
Where can supplementary protectors be used effectively
per code standards?
Eaton series FAZ supplementary protectors can be used
in a number of significant areas. To more clearly illustrate
potential applications, however, let’s first present the NEC’s
definition of a branch circuit:
The circuit conductors between the final overcurrent device
protecting the circuit and the outlets. (Source: NEC)
A branch circuit is that portion of the electrical distribution
system that extends beyond the final branch circuit over-
current protective device and is intended to serve lighting,
appliance, motors, and/or other individual loads.
Typically, the branch circuit overcurrent protective device
(BOPD) will be either a listed molded-case circuit breaker
or a fuse. Supplementary protectors, such as FAZ devices
from the Eaton series, can therefore be added to any of
these branch circuits to “supplement” the branch circuit
protection. Examples of applications ideally suited for these
devices can include:
• Any type of OEM electrical equipment that is fed from
a service panel board and that often requires additional
protection for sensitive internal circuitry and components
(test and medical equipment, copiers and printers, computers
and power supplies, etc.)
• The need for manual reset devices with optional accessories
such as auxiliary contacts and voltage trips to accomplish
fuseless protective circuit designs and enhance operational
diagnostics
• Isolation and protection of control cable, coils, contacts, and
circuit elements of motor control circuits tapped from the load
side of the branch circuit protective device (per NEC 430.72)
• Protection of control circuit transformers, especially in the
secondary where the manual reset protector can be used
to isolate, as well as protect, secondary circuit conductors
and loads
IEC-based miniature circuit breakers, such as the entire FAZ line,
are much more than just conventional supplementary protectors
from an internal design point of view and can provide an ideal
means to enhance the protective capabilities of any circuit.
• As mentioned, they are in full compliance with the pertinent
EN/IEC standards (EN/IEC 60898, EN/IEC 60947-2) for miniature
circuit breakers and can thus be applied, outside of North
America, as full-fledged stand-alone overcurrent protective
devices in both residential and industrial applications
• As this typical let-through current curve shows, they are highly
current limiting devices that appreciably limit the amount of
let-through current and destructive energy within their ratings
to minimize damage levels to downstream loads and circuits
Circuit breakers that are classified as “current limiting” have
the ability to clear damaging short-circuit currents within the
first half-cycle of the fault, resulting in better overall protection
for all circuit components.
• They come in a variety of tripping characteristics, which
is ideal when customizing protection to match specific load
requirements. FAZ supplementary protectors offer a total
of six different protection characteristics for this purpose:
B, C, D, K, S, and Z tripping characteristics
• They feature a number of electrical accessories to enhance
the performance and diagnostic capabilities of control panels,
as well as a means to facilitate panel mounting and wiring
Miniature circuit breaker application
FAZ circuit breakers