Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Reexamination Certificate
2001-09-12
2004-04-06
Leja, Ronald W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
Reexamination Certificate
active
06717782
ABSTRACT:
BACKGROUND
1. Field
The present application relates to a family of resettable circuit breakers that include a reset lockout operation and optionally an independent trip operation, and to power distribution systems in which such circuit breakers are utilized. More particularly, the present application is directed to circuit breakers that include a reset lock out capable of preventing the circuit breaker from resetting if a circuit interrupting portion used for fault protection is not functioning properly and/or if an open neutral condition exists. In addition, a trip portion may be added to the circuit breaker to permit the breaker to be tripped independent of the operation of the circuit interrupting portion.
2. Description of the Related Art
The electrical wiring device industry has witnessed an increasing call for circuit interrupting devices or systems which are designed to interrupt power to various loads, such as household appliances, consumer electrical products and branch circuits. In particular, electrical codes require electrical circuits in home bathrooms and kitchens to be equipped with ground fault circuit protection. Presently available GFCI devices, such as the GFCI receptacle described in commonly owned U.S. Pat. No. 4,595,894, use an electrically activated trip mechanism to mechanically break an electrical connection between one or more input and output conductors. Such devices are resettable after they are tripped by, for example, the detection of a ground fault. In the device discussed in the '894 patent, the trip mechanism used to cause the mechanical breaking of the circuit (i.e., the connection between input and output conductors) includes a solenoid (or trip coil). A test button is used to test the trip mechanism and circuitry used to sense faults, and a reset button is used to reset the electrical connection between input and output conductors.
However, instances may arise where an abnormal condition, caused by for example a lightning strike, occurs which may result not only in a surge of electricity at the device and a tripping of the device but also a disabling of the trip mechanism used to cause the breaking of the circuit. This may occur without the knowledge of the user. Under such circumstances, an unknowing user faced with a GFCI which has tripped may press the reset button which, in turn, will cause the device with an inoperative trip mechanism to reset without the ground fault protection available.
Further, an open neutral condition, which is defined in Underwriters Laboratories (UL) Standard PAG 943A, may exist with the electrical wires supplying electrical power to such GFCI devices. If an open neutral condition exists with the neutral wire on the line (versus load) side of the GFCI device, an instance may arise where a current path is created from the phase (or hot) wire supplying power to the GFCI device through the load side of the device and a person to ground. In the event that an open neutral condition exists, current GFCI devices which have tripped, may be reset even though the open neutral condition may remain.
Commonly owned application Ser. No. 09/138,955, filed Aug. 24, 1998, which is incorporated herein in its entirety by reference, describes a family of resettable circuit interrupting devices capable of locking out the reset portion of the device if the circuit interrupting portion is non-operational or if an open neutral condition exists. Commonly owned application Ser. No. 09/175,228, filed Oct. 20, 1998, which is incorporated herein in its entirety by reference, describes a family of resettable circuit interrupting devices capable of locking out the reset portion of the device if the circuit interrupting portion is non-operational or if an open neutral condition exists and capable of breaking electrical conductive paths independent of the operation of the circuit interrupting portion.
Current resettable circuit breakers with fault protection capabilities, such as the HOM-GFI series of GFCI circuit breakers manufactured by Square-D Company, Palatine, Ill., have line and load power and neutral connections and a switch for controlling power distribution to a load. To provide fault protection, such circuit breakers have sense circuitry and linkage to the switch, which are capable of sensing faults (e.g., ground faults) between the load power and the line neutral conductors and opening the switch. A test button accessible from an exterior of the breaker is used to test the operation of the fault protection portion of the breaker when depressed. However, like conventional resettable receptacles, conventional resettable circuit breakers do not include either a reset lockout or an independent trip portion.
SUMMARY
The present application relates to a family of resettable circuit breakers having fault protection capabilities. The circuit breakers according to the present application include a circuit interrupting portion, a reset portion and a reset lockout portion. The circuit breakers may also include an independent trip portion. The reset lockout portion inhibits the resetting of the circuit breaker if the circuit interrupting portion is non-operational or if an open neutral condition exists. The trip portion operates independently of the circuit interrupting portion and facilitates tripping of the circuit breaker whether or not the circuit interrupting portion is operating properly.
In one embodiment, a GFCI circuit breaker having a housing, a circuit interrupting portion, a reset portion and a reset lockout portion is provided. Preferably, the housing has line phase and load phase connections that are accessible from an exterior of the housing and a conductive path within the housing between the line and load phase connections. The circuit interrupting portion is disposed within the housing and is configured to open the conductive path upon the occurrence of a ground fault. Examples of faults contemplated include ground faults, arc faults, immersion detection faults, appliance leakage faults and equipment leakage faults. The reset portion includes an actuator that is also accessible from the exterior of the housing, and is configured to close the conductive path upon actuation. Preferably, the reset lockout portion inhibits the closing of the conductive path if the circuit interrupting portion is non-operational or if an open neutral condition exists. The reset lockout portion may be an active type lockout that prevents the resetting of the conductive path, or a passive type lockout whose characteristics inherently inhibit the resetting of the conductive path.
The circuit breaker may optionally include a trip portion disposed at least partially within the housing. The trip portion is configured to open the conductive path independently of the operation of the circuit interrupting portion. Thus, in this configuration, if the circuit interrupting portion is not operating properly, the circuit breaker can still be tripped but it cannot be reset, since the reset operation utilizes the circuit interrupting portion when resetting the breaker.
The present application also provides a method for testing the operation of a circuit breaker having a housing with line and load phase connections accessible from an exterior surface of the housing, and a conductive path between the line and load phase connections. The method includes the steps of: 1) manually activating a trip portion of the circuit breaker to open the conductive path and to enable a reset lockout portion that inhibits closing the conductive path; and 2) activating a reset portion to perform a reset operation. During the reset operation a circuit interrupting portion is activated, and if the circuit interrupting portion is operational the circuit interrupting portion disables the reset lockout portion and facilitates closing of the conductive path. If, however, the circuit interrupting portion is not operating properly, the reset lockout portion remains enabled so that closing the conductive path is inhibited.
The present application also provides a circuit interrupting syst
Bradley Roger M.
DiSalvo Nicholas L.
Germain Frantz
Herzfeld David
Stewart Stephen
Leja Ronald W.
Leviton Manufacturing Co. Inc.
Sutton Paul J.
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