Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a continuation-in-part of U.S. patent application Ser. No. 10/884,304 filed on Jul. 2, 2004 now U.S. Pat. No. 7,133,266 and U.S. patent application Ser. No. 10/942,633 filed on Sep. 16, 2004 now U.S. Pat. No. 7,173,799, U.S. patent application Ser. No. 10/884,304 is a continuation of U.S. patent application Ser. No. 09/971,525 filed on Oct. 5, 2001 now U.S. Pat. No. 6,856,498, which is a continuation of U.S. patent Ser. No. 09/718,003 filed Nov. 21, 2000 now U.S. Pat. No. 6,522,510, the contents of which are relied upon and incorporated herein by reference in its entirety, and the benefit of priority under 35 U.S.C. §120 is hereby claimed. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to protection devices, and particularly to protection devices having miswire protection. 
   2. Technical Background 
   Protective devices such as ground fault circuit interrupters (GFCIs) are well known in the art. Their intent is and always has been to protect the electrical power user from electrocution when hazardous ground fault currents are present. 
   Historical problems with these protective devices include the possibility of line/load miswiring in the field by an installer or the eventual failure of the solenoid driving device, typically a silicon controlled rectifier, which causes the interrupter device to become inoperable while electrical power is still present, even under hazardous ground fault conditions. A variety of methods are used to prevent or attempt to prevent miswiring with varying levels of success. Preventing the problems associated with a defective solenoid driving device is inherently more difficult. Labels and installation instruction sheets have been used to prevent miswiring, but can be ignored by the installer. Solenoid burn-out has been revealed by testing the protective device with a test button, but the result of the test can be ignored by the user. 
   Most GFCIs have test and reset buttons having associated instructions molded into the front cover of the device. The instructions typically require the user/homeowner to push the test button monthly. When depressed, the test button generates a current to simulate a fault condition. The device is not providing ground fault protection when the reset button fails to pop out. Accordingly, the user is instructed to replace the device. However, this approach has several drawbacks. 
   Of course, users routinely ignore the instructions printed on the cover of GFCI devices. If the device fails, the user is not aware that the device is not affording any protection. On the other hand, even if the user does press the button and discover that the device has failed, it may be some time before the user replaces the device. 
   Another drawback of the standard devices relates to the fact that a line-load miswire condition is often not tested by the test button. When a device is miswired, it may not protect the user from a fault condition even if it is functioning properly. The hazard will be present at the receptacle outlets even if the device is tripped. In other words, when a miswiring condition is present, the AC power is connected directly to the load terminals. The load terminals are typically connected to the user load terminals (i.e., the receptacles). When the device trips, the conductive path between the line terminals and load terminals is interrupted. However, since the load terminals and the user load terminals are still connected, the device fails to protect the user. In this case, the test and reset buttons may operate normally, giving the user a false sense of security. 
   In one approach that has been considered, a lock-out mechanism has been introduced such that the device will not reset if there is a line-load miswire condition. Power is denied to the load side circuit until the miswire condition is eliminated. Further, if the device is experiencing an internal fault such that the device is not operating properly, the device will likewise, not reset. One drawback to this condition is that it provides the user a disincentive to test. In other words, the user will feel inconvenienced if the device does not work after the test button is pushed. Further, this approach fails to address the scenario described above, when users fail to routinely use the test button. 
   In another approach that has been considered, a fused miswire circuit is disposed in the GFCI. If the device is miswired, the circuit induces a current simulating a fault condition, and the device trips. If the device is wired properly, the circuit again induces a current simulating a fault condition, and the device again trips. However, the current continues to flow until a fuse burns out. One drawback to this approach is that the miswire detection circuit may only be used once, and is forever disabled thereafter. 
   What is needed is a multi-shot method for testing mis-wiring. Further, a device is needed that eliminates any hazard at the receptacle outlets when the device is tripped. 
   SUMMARY OF THE INVENTION 
   The present invention address the needs described above. The present invention provides a multi-shot miswire detection circuit. Further, the present invention eliminates hazardous conditions at the receptacle outlets when the device is tripped. 
   One aspect of the present invention is directed to an electrical wiring protection device that includes a housing assembly having at least one line terminal and at least one load terminal partially disposed therein. A first conductive path is electrically coupled to the at least one line terminal. A second conductive path is electrically coupled to the at least one load terminal, the second conductive path being connected to the first conductive path in a reset state. A fault detection circuit is coupled to the first conductive path. The fault detection circuit is configured to generate a fault detection signal in response to detecting at least one fault condition. A wiring state detection circuit is coupled to the first conductive path. The wiring state detection circuit selectively provides a wiring state detection signal when the at least one line terminal is coupled to a source of AC power, and not providing the wiring state detection signal otherwise. An actuator assembly is configured to provide an actuation stimulus in response to the fault detection signal or the wiring state detection signal. A circuit interrupter is coupled to the actuator assembly. The circuit interrupter is configured to disconnect the first conductive path and the second conductive path in response to the actuation stimulus. 
   In another aspect, the present invention is directed to an electrical wiring protection device that includes a housing assembly having at least one line terminal and at least one load terminal partially disposed therein. A first conductive path is electrically coupled to the at least one line terminal. A second conductive path is electrically coupled to the at least one load terminal, the second conductive path being connected to the first conductive path in a reset state. A fault detection circuit is coupled to the first conductive path, the fault detection circuit being configured to generate a fault detection signal in response to detecting at least one fault condition. A reset button is coupled to the at least one line terminal. A wiring state detection circuit is coupled to the reset button, the wiring state detection circuit selectively providing a wiring state detection signal when the reset button is actuated and the at least one line terminal is coupled to a source of AC power, and not providing the wiring state detection signal otherwise. An actuator assembly is configured to provide an actuation stimulus in response to the fault detection signal or the wiring state detection signal. A circuit interrupter is coupled to the actuator assembly, the circuit interrupter being configured to disconnect the first conductive path and the second conductive path in response to the actuation stimulus. 
   In yet another aspect, the present invention is directed to an electrical wiring protection device that includes a housing assembly including at least one line terminal and at least one load terminal partially disposed therein. A first conductive path is electrically coupled to the at least one line terminal. A second conductive path is electrically coupled to the at least one load terminal, the second conductive path being connected to the first conductive path in a reset state. A fault detection circuit is coupled to the first conductive path, the fault detection circuit being configured to generate a fault detection signal in response to detecting at least one fault condition. A reset mechanism is coupled to the at least one line terminal. A wiring state detection circuit is coupled to the reset mechanism, the wiring state detection circuit selectively providing a wiring state detection signal when the reset mechanism is actuated and the at least one line terminal is coupled to a source of AC power, and not providing the wiring state detection signal otherwise. An actuator assembly is configured to provide an actuation stimulus in response to the fault detection signal or the wiring state detection signal. A circuit interrupter is coupled to the actuator assembly, the circuit interrupter being configured to disconnect the first conductive path and the second conductive path in response to the actuation stimulus. A reset lockout is coupled to the circuit interrupter, the reset lockout preventing the circuit interrupter from connecting the first conductive path and the second conductive path in response to an actuation of the reset mechanism in the absence of the wiring state detection signal. 
   In yet another aspect, the present invention is directed to a circuit interrupting device that includes a housing. A phase conductive path and a neutral conductive path are each disposed at least partially within the housing between a line side and a load side, the phase conductive path terminating at a first connection capable of being electrically connected to a source of electricity, a second connection capable of conducting electricity to at least one load and a third connection capable of conducting electricity to at least one user accessible load, and the neutral conductive path terminating at a first connection capable of being electrically connected to a source of electricity, a second connection capable of providing a neutral connection to the at least one load and a third connection capable of providing a neutral connection to the at least one user accessible load. A circuit interrupting portion is disposed within the housing and configured to cause electrical discontinuity in the phase and neutral conductive paths between the line side and the load side upon the occurrence of a predetermined condition. A reset portion is disposed at least partially within the housing and configured to reestablish electrical continuity in the phase and neutral conductive paths. The circuit interrupting device further includes a reset lockout portion that prevents reestablishing electrical continuity in the phase and neutral conductive paths if a reverse wiring condition exists. The reset portion includes a reset button and at least one reset contact which, when depressed, is capable of contacting at least a portion of the phase conductive path to cause the circuit interrupting portion to operate if the device is properly wired. If the circuit interrupting portion is operational, the circuit interrupting portion is activated to disable the reset lockout portion and facilitate reestablishing electrical continuity in the phase and neutral conductive paths. If the reverse wiring condition exists, the circuit interrupting portion is non-operational, and the reset lockout portion remains enabled so that reestablishing electrical continuity in the phase and neutral conductive paths is prevented. 
   In yet another aspect, the present invention is directed to a circuit interrupting device that includes a housing. A first electrical conductive path is disposed at least partially within the housing and terminating at a first connection, the first connection being capable of electrically connecting to a source of electricity. A second electrical conductive path is disposed at least partially within the housing and terminating at a second connection, the second connection being capable of electrically connecting to at least one load when electrical continuity between the first and second electrical conductive paths is made. A third electrical conductive path is disposed at least partially within the housing and terminating at a third connection, the third connection being capable of electrically connecting to at least one user accessible load when electrical continuity between the first and third electrical conductive paths is made. A circuit interrupting portion is disposed within the housing and configured to break electrical continuity between the first and second conductive paths and between the first and third conductive paths upon the occurrence of a predetermined condition. A reset portion is disposed at least partially within the housing and configured to make electrical continuity between the first and second conductive paths and between the first and third conductive paths. The circuit interrupting device further comprises a reset lockout portion that prevents the making of electrical continuity between the first and second conductive paths and between the first and third conductive paths, if the circuit interrupting portion is non-operational. The reset portion includes a reset button and at least one reset contact which when depressed is capable of contacting at least a portion of one of the first or second conductive paths to cause the circuit interrupting portion to operate if the device is properly wired. If the circuit interrupting portion is operational, the circuit interrupting portion is activated to disable the reset lockout portion and facilitate making of electrical continuity between the first and second conductive paths and between the first and third conductive paths. If the device is reverse wired the circuit interrupting portion is non-operational, the reset lockout portion remains enabled so that making of electrical continuity between the first and second conductive paths and between the first and third conductive paths is prevented. 
   In yet another aspect, the present invention is directed to a circuit interrupting device that includes a housing. At least one input conductor is disposed at least partially within the housing and capable of being electrically connected to a source of electricity. At least one output conductor is disposed within the housing and capable of conducting electrical current to a load when electrically connected to the at least one input conductor. A circuit interrupter is disposed within the housing and configured to break the electrical connection between the input and output conductors in response to the occurrence of a predetermined condition. A reset lock-out is operable between a lock-out position wherein the reset lock-out inhibits resetting of the electrical connection between the input and output conductors, and a reset position wherein the reset lock-out does not inhibit resetting of the electrical connection between the input and output conductors. A reset mechanism is operatively associated with the reset lock-out and the circuit interrupter such that activation of the reset mechanism activates the circuit interrupter if the device is properly wired to facilitate movement of the reset lock-out from the lock-out position to the reset position by the reset mechanism, the reset mechanism does not activate the circuit interrupter if the device is reverse wired such that the reset lock-out remains in the lock-out position. 
   In yet another aspect, the present invention is directed to ground fault circuit interrupting device that includes a housing. At least one input conductor is disposed at least partially within the housing and capable of being electrically connected to a source of electricity. At least one output conductor is disposed within the housing an capable of conducting electrical current to a load when electrically connected to the at least one input conductor. A circuit interrupter is disposed within the housing and configured to break the electrical connection between the input and output conductors in response to the occurrence of a ground fault or test cycle. A reset mechanism includes a reset lock-out responsive to activation of the circuit interrupter so as to be movable between a lock-out position wherein the reset lock-out inhibits resetting of the electrical connection between the input and output conductors and a reset position wherein the reset lock-out does not inhibit resetting of the electrical connection between the input and output conductors. An actuation of the reset mechanism in a proper wiring condition activates the circuit interrupter to facilitate movement of the reset lock-out from the lock-out position to the reset position by the reset mechanism and resets the electrical connection between the input and output conductors. An actuation of the reset mechanism in a reverse wiring condition does not activate the circuit interrupter to facilitate movement of the reset lock-out from the lock-out position to the reset position. 
   In yet another aspect, the present invention is directed to a method for interrupting and resetting electrical connections in fault interrupting devices having a housing. An input conductor is disposed at least partially within the housing and electrically connected to a source of electricity, and an output conductor is disposed at least partially within the housing and capable of conducting electrical current to a load when electrical continuity between the input and output conductors is made The method includes the steps of sensing the occurrence of a predefined condition; breaking electrical continuity between the input and output conductors when the predefined condition is sensed using a circuit interrupting mechanism; enabling a lock-out mechanism to inhibit the making of electrical continuity between the input and output conductors after breaking electrical continuity between the conductors; and activating a reset mechanism to activate the circuit interrupting mechanism to disable the lock-out mechanism and make electrical continuity between the input and output conductors if the input connector is coupled to AC power, and wherein the circuit interrupting mechanism is not activated if the input connector is not coupled to AC power. 
   In yet another aspect, the present invention is directed to a circuit interrupting device that includes a line side connection capable of being electrically connected to a source of electricity. A load side connection is capable of being electrically connected to a load side conductor for providing electricity to a load side. A user load connection is capable of conducting electricity to at least one load for providing an electrical connection to the source of electricity. A first conductive path provides an electrical connection between the line side connection and the user load connection. A second conductive path provides an electrical connection between the line side connection and the load side connection. A reset mechanism is also included. A fault detection circuit is configured to detect a fault condition. A wiring state detector is included, separate from the fault detection circuit, the wiring state detector being configured to test for a proper wiring condition when the reset mechanism is actuated. A circuit interrupter is configured to interrupt the at least one of the first conductive path or the second conductive path when a proper wiring condition or a fault condition is detected. 
   Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
   It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic of a GFCI circuit with miswire protection and an indicator lamp according to one embodiment of the present invention; 
       FIG. 2  is a diagrammatic depiction of a protective circuit with miswire protection according to an alternate embodiment of the invention; 
       FIG. 3  is a diagrammatic depiction of a protective circuit with miswire protection according to another embodiment of the invention; 
       FIG. 4  is a diagrammatic depiction of a protective circuit with miswire protection according to yet another embodiment of the invention; 
       FIG. 5  is a diagrammatic depiction of a protective circuit with miswire protection according to yet another embodiment of the invention; 
       FIG. 6  is a schematic of the electrical wiring devices in accordance with yet another embodiment of the present invention; 
       FIG. 7  is a detail view of a reset lock-out mechanism according to one embodiment of the present invention; 
       FIG. 8  is another detail view of a reset lock-out mechanism; 
       FIG. 9  is yet another detail view of a reset lock-out mechanism; 
       FIG. 10  is yet another detail view of a reset lock-out mechanism; 
       FIG. 11  is yet another detailed view of a reset lock-out mechanism. 
   

   DETAILED DESCRIPTION 
   Reference will now be made in detail to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. An exemplary embodiment of the ground fault circuit interrupter (GFCI) of the present invention is shown in  FIG. 1 , and is designated generally throughout by reference numeral  10 . 
   As embodied herein and depicted  FIG. 1 , a GFCI circuit in accordance with one embodiment is shown. When a differential transformer L 1  senses unequal amounts of current flowing in the hot and neutral conductors due to a ground fault condition, device  10  causes a breaker coil  110  to activate, opening circuit interrupting mechanism  120 . As shown, circuit interrupting mechanism  120  includes hot and neutral bus bars  502 ,  504 . The circuit interrupting mechanism  120  is configured to establish and break connectivity between the hot and neutral AC power lines, and the hot and neutral load lines, respectively. Bus bar  502  and bus bar  504  includes interrupting contacts designed to mate with corresponding contacts located on both AC power lines and the load lines. 
   Device  10  includes a test circuit. The test circuit includes test button  130 . Test button  130  is configured to induce a simulated ground fault when pushed. If the fault detection circuitry is operating properly, breaker coil  110  activates circuit interrupter  120 . 
   GFCI  10  also includes a miswire circuit which uses a fault resistance R 10 , R 13  to create a differential current on the primary of the differential current transformer L 1 . The differential current exceeds the level of differential current that the GFCI has been designed to interrupt, typically 6 milliamperes. The fault resistance R 10 , R 13  is on the line side of interrupting contacts  120 . Note that the ground fault circuit sensing electronics, including IC U1, derive power from the line side terminals of the GFCI. 
   In this embodiment, if GFCI  10  is miswired such that AC power is connected to the load terminals, nothing visible happens if the GFCI is tripped. On the other hand, if the GFCI is in the reset condition, it will immediately trip when powered. Thus, when device  10  is miswired, the current flowing through the fault resistance R 10 , R 13 , will be interrupted when the device trips. Resistors R 10 , R 13  will remain intact because the estimated time it takes for the fault resistors R 10 , R 13  to “clear,” or burn out, is greater than 50 ms, and typically in the 300 ms range. On the other hand, the trip time of the GFCI is less than or equal to 25 ms. Thus, fault resistors R 10 , R 13  do not have enough time to clear. If the device is reset in the miswired condition, the device trips out immediately thereafter. This cycle will continue until the device is wired correctly, i.e., when power is connected to the GFCI line terminals. 
   Thus, a properly wired device  10  operates as follows. When electrical power is connected in a correct manner to the line terminals, a differential current is created by the fault resistance R 10 , R 13  when power is applied to the device. If the device is reset before power is applied, the device trips as a result of this differential current. If the device is already in the tripped condition before power is applied, nothing visible happens. However, because the fault resistor is on the line side of the interrupting contacts  120 , current through fault resistance R 10 , R 13  continues to flow, regardless of interrupting contacts  120  being open. This internal differential current, created by the fault resistance R 10 , R 13  clears itself in a short time, typically 300 ms. The clearance time is a function of the resistors&#39; power rating. Thus, a resistor(s) is selected having a power rating that is greatly exceeded by the current. Another option is to provide a fuse F 1  that is placed in series with the fault resistances R 10 , R 13 . The fuse is selected such that its I 2 t rating is less than the resistors. Accordingly, the fuse opens instead of the fault resistors R 10 , R 13 . The term “resistive element” as used herein may refer to either a resistance or a fuse. Once the device has been properly wired and the fault has been cleared, the device can be reset and provide its normal protective functions. 
   Device  10  also includes indicator circuit. The indicator circuit includes a light  140  that is configured to have multiple indication meanings. The indicator circuit includes resistors R 11 , R 12 , R 14 , and indication device  140 . In one embodiment, light  140  is implemented using a neon light. Those skilled in the art will recognize that light  140  may be implemented using LEDs or other such means. The first function of light  140  is as a trip indicator. The light is off if the GFCI is in the reset condition, and illuminates if the GFCI trips. The second function of light  140  is to indicate miswiring. A third function of light  140  is to notify the user that the solenoid-driving device is defective and that the GFCI is no longer operational. 
   The indicating circuit operates as follows. When the GFCI is wired properly, i.e., power from the supply source is connected to the line terminals and not the load terminals, and the device is reset, light  140  is off, as the line disconnecting contacts  120  are closed, resulting in no voltage across light  140  and resistor R 12 . If the GFCI trips for any reason, light  140  energizes as a result of line voltage being applied across light  140  and resistors R 12  and R 11 . When the device is reset, voltage is removed and light  140  turns off. If the device is miswired for any reason, light  140  is off when the GFCI is reset, but when the device trips in this condition, there is not return path to neutral through resistor R 11 , and light  140  does not turn on as it would if the GFCI were wired properly. This feature is not dependent on the fault resistance R 10 , R 13 ; therefore, if the miswire detection circuit has been previously used and the fault resistance cleared, miswire detection is still possible by exercising this light in conjunction with tripping out the GFCI. 
   Indicating a defective solenoid driving device, such as SCR Q 1 , is achieved with the addition of a resistor R 14 . With resistor R 14  in the circuit, light  140  energizes when the SCR Q 1  short circuits and a path to supply neutral develops. When this occurs, and the device is reset, the GFCI trips, energizing light  140  through resistor R 14 . Continuously applied line voltage to the solenoid occurring as a result of a shorted SCR Q 1  causes the trip solenoid (coil  110 ) to open within a few seconds. Coil  110  burns out since it is continuously energized, so it cannot trip again after the device is reset. When the GFCI is reset in this condition, light  140  remains energized, indicating a defective solenoid driving device. The value of resistor R 14  must be kept low relative to the value of resistor R 12  as a voltage divider occurs between resistors R 12  and R 14  which limits the voltage across light  140 . A neon lamp needs a minimum of about 60 volts to arc over and energize. A value of 33K for resistor R 14  is suitable for this embodiment, which provides for about 66 volts across the neon lamp at a worst case line voltage of  102  VAC. Computing different values for resistors R 11 , R 12 , and R 14  based on different types of lights  140  is considered within the capabilities of one skilled in the art. 
   Of course, device  10  also includes a reset button which is not shown in  FIG. 1  for clarity of illustration. As described in more detail in  FIGS. 4–11 , a multi shot miswire detection circuit may be implemented as part of the reset mechanism. 
   As embodied herein and depicted in  FIG. 2 , a schematic diagram of a miswire protection circuit in accordance with another embodiment of the present invention is disclosed. The embodiment is generalized to apply to different protective devices such as ground fault circuit interrupters (GFCIs) or devices intended to interrupt ground faults from personnel contact with a power line conductor, arc fault circuit interrupters (AFCIs) intended to interrupt line current which if allowed to continue could cause an electrical fire, combination devices that provide both AFCI and GFCI protection, or the like. 
   Accordingly, the protective device  10  includes a protective circuit  402  that is configured to detect one or more fault conditions (arc fault, ground fault, etc.). In response to detecting a fault, protective circuit  402  drives electronic switching device  404  (SCR) into a conducting state to thereby energize solenoid  406 . Solenoid  406  opens interrupting contacts  408  in an energized state. Note that solenoid  406  receives power from the line conductors. Thus, when AC power is applied to the load terminals, no power is applied to either protective circuit  402 , SCR  404 , solenoid  406 , or multi-shot miswire detection circuit  410 . 
   With regard to the miswire circuit, fault resistors R 10 , R 13 , switch S 1 , and fuse F 1 , have the same functions as previously described in  FIG. 1 . The indicator circuit, i.e., resistors R 11 , R 12 , R 14 , and light  140  also have the same functions as previously described. When power is miswired to the load terminals and the protective device is reset such that interrupting contacts  408  are closed, current flows through normally closed switch S 1 , fuse F 1 , fault resistors R 10 , R 13  and the gate-cathode junction of SCR  404 , energizing solenoid  406  and tripping the interrupting contacts  408 . Fuse F 1  and fault resistors R 10 , R 13  are chosen to withstand the current flow for the time that power is applied to the load terminals to the moment when interrupting contacts  408  open, approximately 25 milliseconds. If line power is connected as intended to the line terminals of the protective device, current flows through normally closed switch S 1 , fuse F 1 , fault resistors R 10 , R 13 , and the gate cathode junction of SCR  404  until such time as fuse F 1  clears, after which it is possible to accomplish a resetting of the interrupting contacts  408 . Solenoid  406  is designed not to burn out during the interval that SCR  404  is conductive, which interval is designed to be approximately 100 milliseconds. In this manner the protective functions described in  FIG. 1  are provided without necessarily requiring a differential current transformer L 1  in the construction of the protective device nor attachment of the fault resistor and fuse circuit to both the hot and neutral line conductors. If an electronic switching device other than an SCR is used, e.g., a bipolar transistor, the connections shown here are being made to the gate of the SCR would instead be made to the base of the bipolar transistor. “Gate” and “base” are intended to have an equivalent meaning in this specification and claims. 
   As embodied herein and depicted in  FIG. 3 , a schematic of an electrical wiring device  10  in accordance with another embodiment of the present invention is depicted. Device  10  is configured to sense and detect fault conditions that may occur in the electrical distribution system, as well as simulated fault conditions, that are either manually or automatically generated. Fault conditions may include arc faults, ground faults, or both. 
   Device  10  includes three main portions: a detection circuit  1300 , a miswire detection circuit  1308 , and tripping mechanism  801 . Detection circuit  1300  includes differential transformer  100 . Transformer  100  is configured to sense a difference in the current between the hot and neutral conductors connected respectively to terminals  20  and  200 . The difference current is generated by a fault current to ground when a person is contacting ground at the same time as an inadvertently exposed hot conductor connected to terminals  300  or  48  (the current through the person flows through the hot conductor but does not return through the neutral conductor.) The sensed signal is detected by detector  104  which can include any of a variety of integrated detection circuits, such as the RV  4141  manufactured by Fairchild Semiconductor Corporation. The detected signal turns on SCR  106  to actuate solenoid  52  to trip the trip mechanism  801  as has been described. 
   In one embodiment of the present invention, trip mechanism  801  includes an auxiliary switch  812 . Auxiliary switch contacts  812  open when trip mechanism  801  is in the tripped position. If SCR  106  has reached end-of-life and is permanently ON, auxiliary switch  812  assures that solenoid  52  is not permanently connected to a source of current. Otherwise, solenoid  52  may become thermally damaged by continuous exposure to the current, and be unable to operate trip mechanism  801  to interrupt a fault condition. If SCR  106  has reached end of life, and reset button  822  is depressed to close the various contacts associated with trip mechanism  801 , auxiliary switch  812  closes. In response thereto, solenoid  52  will immediately trip the mechanism again. Thus, auxiliary contacts  812  ensure that trip mechanism  801  will not remain reset when an end-of-life condition has been reached. Accordingly, load terminals  30  and  300 , and receptacle terminals  42  and  48  may not be permanently connected to line terminals  200  and  20  when SCR  106  has reached end of life, sometimes referred to as safe failure of device  10 . 
   Device  10  also includes a trip indicator  1302 . Indicator  1302  is coupled to auxiliary switch  812 . When trip mechanism  801  is in the tripped state, indicator  1302  is illuminated. Thus, when the indicator is activated, the user realizes that device  10  is the cause of the power interruption in the circuit. Indicator  1302  furthermore demonstrates to the user if auxiliary switch  812  is operational. Those of ordinary skill in the art will recognize that indicator  1302  may be implemented as a lamp, an annunciator, or both. In the ON state, indicator  1302  may transmit continuously or intermittently. Device  10  also may include a “power-on” indicator  1304 . Dashed line  1306  between indicator  1304  and DC ground represents the power-on indicator circuit. Indicator  1304  is configured to demonstrate that power is being delivered to the load terminals  30  and  300 , and receptacle terminals  42  and  48 . Those of ordinary skill in the art will recognize that indicator  1304  may be implemented as a lamp, an annunciator, or both. In one embodiment, miswire detection circuit  1308  includes a miswire resistor  1310  in series with an optional switch  1312 . Switch  1312 , if provided, is open during manufacturing assembly to facilitate electrical testing of device  10 . After device  10  has been tested, switch  1312  is closed during assembly, before device  10  is in the commercial stream. When device  10  is properly wired, i.e., the source of power of the electrical distribution system is connected to line terminals  20  and  200 , a constant current flows through resistor  1310 . Resistor  1310  is configured to open circuit when the electrical current has flowed for a predetermined time. In one embodiment the predetermined time is about 1 to 5 seconds. After resistor  1310  has open circuited, reset button  822  may be depressed, enabling trip mechanism  801  to enter the reset state. Optionally, a fuse or an air gap device (not shown) can be connected in series with resistor  1310  whereby resistor  1310  remains closed and the fuse or air gap device is responsible for open circuiting within the predetermined time. As described in more detail below, a multi-shot miswire detection circuit may be implemented as part of the mechanism that includes reset button  822 . See  FIGS. 4–11 . 
   Referring back to  FIG. 3 , device  10  includes auxiliary switch  1404  in accordance with an alternate embodiment of the present invention. In this embodiment, the auxiliary switch  1404  is disposed between the detector  104  power supply line and the detector output. Of course, the detector output is connected to SCR  106  control input. When switch  1404  is closed, SCR  106  is turned ON. 
   If device  10  is miswired, the current fails to flow through resistor  1310  in the manner described above and resistor  1310  fails to open-circuit. Instead, the current through resistor  1310  is sensed by differential transformer  100  as a differential current. Detector  104  interprets the differential current as a fault condition. Accordingly, detector  104  signals the control input to SCR  106 . SCR  106  is turned ON to thereby actuate solenoid  52 . Solenoid  52  generates a magnetic field and mechanism  801  is tripped. Thus, the current flowing through resistor  1310  is interrupted before resistor  1310  open-circuits. The duration of the current flow through resistor  1310  is approximately the response time of device  10 . In other words, the current flowing through resistor  1310  is interrupted in less than 0.1 seconds. As such, the duration of the current flow is too brief to cause opening of resistor  1310 . If reset button  822  is depressed to reset trip mechanism  801 , current starts to flow again through resistor  1310 . However, the current is again detected and device  10  is immediately tripped. Accordingly, device  10  will repeatedly trip when the source of power of the power distribution system is miswired to the load terminals. 
   Accordingly, the present invention is configured such that contact pair  808 / 804  and contact pair  804 / 800  are open (tripped) when device  10  is miswired. The tripped state prevents the AC power source, having been miswired to the load terminals ( 30 , 300 ), from permanently providing power to the receptacle terminals even though a fault condition in the user attachable load might be present. Although the miswire circuit has been described with respect to a resistor  1310  that opens when the device has been properly wired, any number of fusible links familiar to those skilled in the art may be employed. The fusible link may open (clear) due to a predetermined fusing characteristic. The fusible link may be configured to open when a nearby resistance heats the fuse link to a predetermined temperature. 
   Those of ordinary skill in the art will recognize that there are other miswire protection methods configured to permanently block the ability to reset device  10  until device  10  has been properly wired. For example, resistor  1310  may provide a physical block that prevents interference between escapement  830  and latch  826 . See  FIG. 8 . When device  10  is properly wired, resistor  1310  conducts a steady current which causes resistor  1310  to heat sufficiently to melt solder on its solder pads. A spring bias (not shown) may be implemented to urge resistor  1310  to dislodge. Dislodged resistor  1310 , no longer providing a physical block, permits reset button  822  to establish the interference between escapement  830  and  826 . Accordingly, until the device is wired properly, resistor  1310  will not be dislodged and device  10  cannot be reset. 
   As will be described in more detail relative to  FIGS. 4–11 , a multi-shot miswire detection circuit may also include a miswire lockout mechanism that prevents reset unless the device is properly wired. 
   An AFCI or other protective device may be protected from miswiring by including trip mechanism  801  and a miswiring circuit  1308 ′. Sensor  100 ′ and detector  104 ′ are configured to sense and detect the particular fault condition(s) being protected. The miswire resistor may be configured to generate a simulated fault signal. As described above, the miswire resistor clears when device  10  is properly wired. As such, the simulated fault condition is likewise cleared, permitting the trip mechanism  801  to reset. Alternatively, the miswire resistor may be configured to generate a trip signal that does not represent a fault condition. The trip signal similarly interrupts when device  10  is properly wired, permitting the trip mechanism  801  to reset. For example, miswire resistor  1310 ′ generates a trip signal to turn SCR  106  ON. Solenoid  52  is activated until device  10  is properly wired, whereupon resistor  1310 ′ is cleared to create an open circuit. 
   As embodied herein and depicted in  FIG. 4 , a miswire protection circuit in accordance with another embodiment of the present invention is disclosed. The circuit may also be referred to as a wiring state detection circuit because the circuit operates when the device is properly wired and does not operate if miswired. This embodiment is very similar to the embodiment depicted in  FIG. 2  and is also generalized to apply to different protective devices such as ground fault circuit interrupters (GFCIs) or devices intended to interrupt ground faults from personnel contact with a power line conductor, arc fault circuit interrupters (AFCIs) intended to interrupt line current which if allowed to continue could cause an electrical fire, combination devices that provide both AFCI and GFCI protection, or the like. Therefore, the protective device  10  includes a protective circuit  402  that is configured to detect one or more fault conditions (arc fault, ground fault, etc.). 
   In this embodiment, the miswire circuit  410  is disposed between the hot line conductor and the input to SCR  404 . One difference between this embodiment and the embodiment depicted in  FIG. 2  is that switch S 1  is coupled to the reset button. When the reset button is depressed, switch S 1  is closed. If device  10  is properly wired, current flows through the miswire circuit  410  to activate SCR  404 . SCR  404  energizes solenoid  406 . The armature in solenoid  406  is configured to drive a miswire lockout mechanism (not shown in  FIG. 4 ) into an unlocked state, permitting the circuit interrupting contacts  408  to close (reset.) However, if AC power is connected to the load terminals, miswire circuit  410  is not connected to a source of power. When the reset button is depressed, solenoid  406  is not energized and the armature fails to dislodge the miswire lockout. Note that the indicator circuit including resistors R 11 , R 12 , R 14 , and light  140  have the same functions as previously described in the previously disclosed embodiments. 
     FIG. 5  is another embodiment of the multi-shot miswire circuit. In this case, switch S 1  is connected in parallel with SCR  404 . If device  10  is properly wired, current flows through solenoid  406 . Again, the armature moves in response thereto. The armature in solenoid  406  is configured to drive miswire lockout mechanism (not shown) into an unlocked state, permitting the circuit interrupting contacts  408  to close (reset.) However, if AC power is connected to the load terminals, switch S 1  is not connected to a source of power. When the reset button is depressed, solenoid  406  is not energized and the armature fails to dislodge the miswire lockout. 
     FIG. 6  is a four pole version of the embodiment depicted in  FIG. 4 . Thus, this embodiment is very similar to the embodiment shown in  FIG. 2  as well. A four pole device includes four circuit interrupters—two for the hot conductors and two interrupters for the neutral conductors. For example, when the device is tripped, the connection between the hot line conductor and the hot load conductor is interrupted. In addition, the connection between the hot line conductor and the hot user load conductor (i.e., the hot outlet receptacle) is likewise interrupted. The neutral side of the device is identical. When the device is tripped, the connection between the neutral line conductor and the neutral load conductor is interrupted. In addition, the connection between the neutral line conductor and the neutral user load conductor (i.e., the neutral outlet receptacle) is interrupted. 
   The miswire circuit operates as follows. When the reset button is depressed, switch S 1  is closed. If device  10  is properly wired, current flows through the miswire circuit  410  to activate SCR  404 . SCR  404  energizes solenoid  406 . The armature in solenoid  406  is configured to drive a miswire lockout mechanism (not shown in  FIG. 6 ) into an unlocked state, permitting the circuit interrupting contacts  408  to close (reset.) 
   However, if AC power is connected to the load terminals, miswire circuit  410  is not connected to a source of power. When the reset button is depressed, solenoid  406  is not energized and the armature fails to dislodge the miswire lockout. Again, the indicator circuit including resistors R 11 , R 12 , R 14 , and light  140  have the same functions as previously described in the previously disclosed embodiments. 
   Referring to  FIG. 7 , a three-pole version of the miswire circuit depicted in  FIG. 5  is disclosed. In a three pole arrangement, the circuit interrupter  408  includes an additional circuit interrupter disposed between the neutral line conductor and the neutral user load (receptacle outlet). In this embodiment, switch S 1  is connected in parallel with SCR  404 . If device  10  is properly wired, current flows through solenoid  406  and the armature moves in response. The armature in solenoid  406  is configured to drive miswire lockout mechanism (not shown) into an unlocked state and the circuit interrupters  408  are tripped. However, if AC power is connected to the load terminals, switch S 1  is not connected to a source of power. When the reset button is depressed, solenoid  406  is not energized and the armature fails to dislodge the miswire lockout. 
   As embodied herein and depicted in  FIGS. 8–11 , a detail view of a reset lock-out mechanism is disclosed.  FIGS. 8–11  assume that the device is properly wired. Initially, when device  10  is in the tripped condition, latch  826  is not coupled to escapement  830 . 
   Referring to  FIG. 8 , reset is effected by applying a downward force to reset button  822 . Shoulder  1400  on reset pin  824  bears downward on switch S 1  as previously described. In  FIG. 9 , the wiring state detection circuit (See  FIGS. 4–7 ) is properly powered and provides a signal that causes solenoid  52 ,  406  to activate armature  51 . Armature  51  moves in the direction shown, permitting hole  828  in latch  826  to become aligned with shoulder  1400 . The downward force applied to reset button  822  causes shoulder  1400  to continue to move downward, since it is no longer restrained by shoulder  1400 . Referring to  FIG. 10 , since shoulder  1400  is disposed beneath latch  826 , it is no longer able to apply a downward force on latch  826  to close electrical switch S 1 . Accordingly, switch S 1  opens to thereby terminate the activation of solenoid  52 ,  406 . Armature  51  moves in the direction shown in response to the biasing force of spring  834  and latch  826  is seated on latching escapement  830 . As a result, device  10  is reset. 
   Referring to  FIG. 11 , a user accessible test button  50  is coupled to the trip mechanism. When test button  50  is depressed, device  10  is tripped by a mechanical linkage  1402 . In particular, mechanical linkage  1402  urges latch  826  in the direction shown when a force is applied to test button  50 . Latch  826  counteracts the biasing force of spring  834  causing the hole  828  in latch  826  to become aligned with escapement  830 . Contacts  800 ,  804 , and  808  become separated, to trip device  10 , because latch  826  is no longer restrained by escapement  830 . 
   As previously described, device  10  is reset when solenoid  52 ,  406  is energized, causing armature  51  to unlock the reset lockout mechanism. However, if the protective device  10  is not properly wired, armature  51  cannot be activated. As a result, the mechanical barrier is not removed and the trip mechanism is prevented from resetting. The physical barrier prevents the protective device from being resettable if there is a miswire condition. 
   The four-pole circuit interrupter design with indicator may be implemented using a sandwiched cantilever mechanism. The indicator may be a visual and/or audible indicator. A visual indicator may be of various colors. The indicator may be steady or intermittent, e.g., a flashing red indicator. Reference is made to U.S. patent application Ser. No. 10/729,392 and U.S. patent application Ser. No. 10/729,396, which are incorporated herein by reference as though fully set forth in their entirety, for a more detailed explanation of a protective four pole device with a lockout and indicator. 
   It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Technology Category: 5