Abstract:
The present invention is directed to an electrical wiring device that includes a plurality of line terminals and a plurality of load terminals. The plurality of line terminals are coupled to the plurality of load terminals in a reset state and decoupled therefrom in a tripped state. A wiring state detection circuit is coupled to the plurality of line terminals or the plurality of load terminals. The wiring state detection circuit is configured to monitor an electrical signal propagating on the plurality of line terminals or the plurality of load terminals and derive at least one signal characteristic therefrom. The wiring state detection circuit is configured to automatically determine a wiring state of the electrical wiring device based on the at least one signal characteristic upon device installation or device reinstallation. The wiring state detection circuit generates a miswire detection signal if the wiring state is determined to be in a miswired wiring state and generating a proper wiring detection signal if the wiring state is determined to be in a proper wiring state. A fault detection circuit is coupled to the plurality of line terminals, the fault detection circuit being configured to generate a fault detection signal in response to detecting at least one fault condition. A circuit interrupter assembly is responsive to the wiring state detection circuit and the fault detection circuit. The circuit interrupter is configured to drive the plurality of line terminals and the plurality of load terminals into the tripped state in response to either the fault detection signal or the miswire detection signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 11/870,815 filed on Oct. 11, 2007, which is a continuation of U.S. patent application Ser. No. 11/237,399 filed on Sep. 28, 2005, 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 electrical wiring devices, and particularly to protective wiring devices. 
     2. Technical Background 
     AC power is provided to a house, building or other such facilities by coupling one or more breaker panels to an electrical distribution system, or another such source of AC power. The breaker panel distributes AC power to one or more branch electric circuits installed in the structure. The electric circuits typically include one or more receptacle outlets and may further transmit AC power to one or more electrically powered devices, commonly referred to in the art as load circuits. The receptacle outlets provide power to user-accessible loads that include a power cord and plug, with the plug being insertable into the receptacle outlet. Because certain types of faults have been known to occur in electrical wiring systems, each electric circuit typically employs one or more electric circuit protection devices. Electric circuit protective devices have been disposed within the breaker panel, receptacle outlets, plugs and the like. 
     Both receptacle wiring devices and electric circuit protective wiring devices in general, are disposed in an electrically non-conductive housing. The housing includes electrical terminals that are electrically insulated from each other. The line terminals are intended to be connected by the installer to a power source of an electrical distribution system, and the feed-through load terminals are intended to be connected to provide the electrical power to downstream receptacles, lighting fixtures, switches, and the like. Receptacle load terminals are electrically connected to the feed-through load terminals. The receptacle load terminals are configured to align with the blades of an attachment plug in order to provide source power by way of the plug to a user attachable load. Protective devices typically include a circuit interrupter that connects the line terminals to the load terminals in the reset state and disconnects the line terminals from the feed-through and receptacle load terminals in the tripped state. The circuit interrupter trips when a fault condition occurs. There are various types of protective devices including ground fault circuit interrupters (GFCIs), ground-fault equipment protectors (GFEPs), and arc fault circuit interrupters (AFCIs). Some protective devices include both GFCIs and AFCIs. 
     An arc fault typically manifests itself as a high frequency current signal. Accordingly, an AFCI may be configured to detect various high frequency signals and de-energize the electrical circuit in response thereto. A ground fault occurs when a current carrying (hot) conductor creates an unintended current path to ground. A differential current is created between the hot/neutral conductors because some of the current flowing in the circuit is diverted into the unintended current path. The unintended current path represents an electrical shock hazard. Ground faults, as well as arc faults, may also result in fire. 
     A “grounded neutral” is another type of ground fault. This type of fault may occur when the load neutral terminal, or a conductor connected to the load neutral terminal, becomes grounded. While this condition does not represent an immediate shock hazard, it may lead to serious hazard. As noted above, a GFCI will trip under normal conditions when the differential current is greater than or equal to approximately 6 mA. However, when the load neutral conductor is grounded the GFCI becomes de-sensitized because some of the return path current is diverted to ground. When this happens, it may take up to 30 mA of differential current before the GFCI trips. Therefore, if a double-fault condition occurs, i.e., if the user comes into contact with a hot conductor (the first fault) when simultaneously contacting a neutral conductor that has been grounded on the load side (the second fault), the user may experience serious injury or death. 
     Another type of fault condition is commonly referred to as miswiring, or reverse wiring. A protective device may be miswired during installation by connecting the load terminals to AC power. When this happens, the circuit interrupter may be unable to interrupt the flow of electrical current to the receptacle terminals when a fault condition is present. Unfortunately, protective devices do not typically alert the user to the miswire condition. Thus, it is not until damage or injury occur that the miswired condition is evident. As noted above, receptacle load terminals and the feed-through load terminals may be permanently connected by an electrical conductor. When a device is properly wired, the circuit interrupter typically includes a single breaker that breaks the connection between the line terminals and both the feed-through load terminals and the receptacle load terminals. In other words, the typical protective device is not configured to remove power from the user load when a hazardous fault condition is extant. Accordingly, when a receptacle type device is reverse wired, unprotected AC power may be available at the receptacle load terminals when the circuit interrupter is in the tripped state. 
     Protective devices may be equipped with a test button. However, while test buttons may be determine the ability of the protective device to detect and interrupt a fault condition, they are typically not configured to reveal a reverse-wired condition. Accordingly, many devices are provided with wiring instruction sheets. Unfortunately, instruction sheets are often ignored by installers. 
     In one approach that has been considered, a protective device is equipped with a barrier(s) that is/are configured to prevent circuit reset until AC voltage is present at the line terminals. The barrier may alert the installer to the reverse-wired condition by preventing reset of the device and by denying AC power to the feed-through load. This approach may be effective during the original installation of the protective device. However, once proper installation is effected the barrier is deactivated and inoperative during a subsequent re-installation. This drawback is further exacerbated by the fact that the installation instructions are unlikely to be available for any re-installation. 
     In another approach that has been considered, a protective device may be equipped with a fuse that is configured to prevent circuit interrupter reset until AC voltage is provided to the line terminals. The fuse circuit prevents reset of the device and denies power to the feed-through load until proper wiring is effected. Once proper wiring is effected, the fuse blows and is no longer available to detect a reverse-wired condition if there is a reinstallation. Again, making matters worse, the installation instructions are likely to be lost and not available for any re-installation. 
     In another approach that has been considered, a protective device may be equipped with one or more sets of isolating contacts disposed between the feed-through load terminals and the receptacle load terminals. In this approach, the set of isolating contacts may be controlled by a miswire detection circuit. In the event of a miswire condition, the miswire detection circuit is configured to either open (or prevent closure) of the isolating contacts. After a proper wiring condition is detected, the miswire detection circuit is configured to either close (or permit closure) of the isolating contacts. Like the other approaches considered above, the miswire detection circuit is ineffectual after an initial proper installation, and is no longer available to detect a reverse-wired condition during any reinstallation. Thus, the isolating contacts are closed in spite of a reverse wired condition. 
     What is needed is a protective device that denies power to the protected circuit, including receptacle terminals, during a miswired condition. Further, a protective device, responsive to the miswired condition during each and every installation, is needed. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the needs described above. In particular, the present invention is directed to a protective device that denies power to the protected circuit, including receptacle terminals, during a miswired condition. More importantly, the protective device of the present invention is responsive to the miswired condition during each and every installation. 
     One aspect of the present invention is directed to an electrical wiring device that includes a plurality of line terminals and a plurality of load terminals. The plurality of line terminals are coupled to the plurality of load terminals in a reset state and decoupled therefrom in a tripped state. A wiring state detection circuit is coupled to the plurality of line terminals or the plurality of load terminals. The wiring state detection circuit is configured to monitor an electrical signal propagating on the plurality of line terminals or the plurality of load terminals and derive at least one signal characteristic therefrom. The wiring state detection circuit is configured to automatically determine a wiring state of the electrical wiring device based on the at least one signal characteristic upon device installation or device reinstallation. The wiring state detection circuit generates a miswire detection signal if the wiring state is determined to be in a miswired wiring state and generating a proper wiring detection signal if the wiring state is determined to be in a proper wiring state. A fault detection circuit is coupled to the plurality of line terminals, the fault detection circuit being configured to generate a fault detection signal in response to detecting at least one fault condition. A circuit interrupter assembly is responsive to the wiring state detection circuit and the fault detection circuit. The circuit interrupter is configured to drive the plurality of line terminals and the plurality of load terminals into the tripped state in response to either the fault detection signal or the miswire detection signal. 
     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 diagram of a protective device in accordance with a first embodiment of the present invention; 
         FIG. 2  is a schematic of the protective device shown in  FIG. 1  in a miswired state; 
         FIG. 3  is a schematic diagram in accordance with a second embodiment of the present invention; 
         FIG. 4  is a schematic diagram in accordance with a third embodiment of the present invention; 
         FIGS. 5A-5E  are timing diagrams illustrating the miswire protection functionality of the present invention; 
         FIG. 6  is a schematic of a miswire lockout circuit in accordance with a fourth embodiment of the present invention; 
         FIG. 7  is a front cover view of a protective device in accordance with the present invention; 
         FIGS. 8-9  are cross-sectional views of the protective device in accordance with an embodiment of the present invention; and 
         FIGS. 10-11  are cross-sectional views of the protective device in accordance with an alternate embodiment of the present invention. 
     
    
    
     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. Example embodiments of the protective device of the present invention are shown starting at  FIG. 1 , and are designated generally throughout by reference numeral  10 . 
     As described in more detail below, protective device  10  includes a plurality of line terminals coupled to a plurality of load terminals by way of at least one conductive path. When the plurality of load terminals are connected to source voltage, device  10  monitors signal propagation characteristics on the at least one conductive path. Device  10  is configured such that the step of monitoring commences each time source voltage is applied to the plurality of load terminals. A miswire trip signal is generated based on a predetermined signal propagation characteristic. An electrical discontinuity is introduced in the at least one conductive path in response to the trip signal. 
     Referring to  FIG. 1  and  FIG. 2 , a schematic diagram of a protective device  10  in accordance with a first embodiment of the present invention is disclosed.  FIG. 2  is a schematic diagram of the protective device in a miswired state. 
     Device  10  typically includes a hot line terminal  12  and a neutral line terminal  14 . Line terminals  12 ,  14  are coupled to sensor  26  and sensor  28  by way of a hot conductive path and a neutral conductive path, respectively. The conductive paths are connected to circuit interrupter  24 . Circuit interrupter  24  couples the line terminals ( 12 ,  14 ) to the feed-through terminals ( 16 ,  18 ) and the receptacle terminals ( 20 ,  22 ) when circuit interrupter  24  is in a reset state. Those of ordinary skill in the art will understand that load terminals  16 ,  18 , may be connected to wires coupled to one or more downstream receptacles, or switches, in a daisy chain arrangement. Receptacle terminals  20 ,  22  are configured to mate with an appliance plug connected by a power cord to an electrical appliance or a similar electrical load. Of course, circuit interrupter  24  disconnects the line terminals from both the load terminals  16 ,  18  and the receptacle load terminals  20 ,  22  in the tripped state. 
     In one embodiment of the present invention, isolating contacts  30  are configured to disconnect one or more of the feed-through terminals  16 ,  18  from a corresponding receptacle terminal  20 ,  22 . Such contacts are open when the device has been miswired. Isolating contacts  30  are coupled operably to circuit interrupter  24  such that they are open when circuit interrupter  24  is in the tripped state. Alternatively, isolating contacts  30  are coupled operably to a supplementary interrupter (not shown) such that they are open when device  10  has been miswired. 
     Device  10  operates as follows. Sensor  26  is a differential transformer which is configured to sense load-side ground faults. Sensor  28  is a grounded neutral transformer and is configured to generate and couple a fault signal to the differential transformer in the event of a grounded-neutral fault condition. Differential transformer  26  and grounded-neutral transformer  28  are coupled to detector circuit  32 . Power supply circuit  34  conditions AC power by providing a DC (V+) voltage supply for GFCI detector circuit  32 . Detector  32  provides a fault detect output signal  36  in response to sensor inputs from transformers ( 26 ,  28 .) Output signal  36  is directed into filter circuit  38 . The filtered output signal is provided to the control input of SCR  40 . SCR  40  is turned ON to energize solenoid  42  when it is turned ON by the filtered output signal. Solenoid  42  drives trip mechanism  44  to open the interrupting contacts in circuit interrupter  24 . 
     The trip solenoid  42  remains energized until the contacts in circuit interrupter  24  are tripped. The open contacts interrupt the flow of fault current. The sensor output signal generated by transformer  26  is also terminated by the interruption of the fault current. When the transformer signal ceases, the detector output signal changes state turning SCR  40  OFF. Once SCR  40  is OFF, solenoid  42  de-energizes within a time period that is less than about 25 milliseconds. After the fault condition has been eliminated, reset button  46  may be employed to reset circuit interrupter  24 . 
     Device  10  also is equipped with a test facility. In particular, when test button  48  is depressed by a user, a simulated fault condition is generated. The simulated fault condition is used to check the operative condition of GFCI  10 . Circuit interrupter  24  will trip if the device is properly operating. Power may be restored to device  10  after a successful test by pressing reset button  46 . In an alternative embodiment of the present invention, the test facility can be actuated by depressing the reset button  46 . Switch contacts in communication with reset button  46  close the test circuit to initiate the test in the manner previously described. 
     Device  10  includes a miswire lock-out circuit  50 . Miswire lock-out circuit  50  includes a voltage sensor  52  that monitors the polarity of the AC (or DC) source voltage. Current transformer  54  monitors the direction of the current (i.e., current polarity) from the voltage source to load  60 . When device  10  is properly wired as shown in  FIG. 1 , the current transformer also monitors the current through a user attachable load  62 . If the polarity of the current and the polarity of the voltage match each other, processor  56  determines that device  10  has been properly wired. 
     Referring to  FIG. 2 , if the current and voltage polarities oppose each other, processor  56  determines that device  10  has been reverse wired. In response to a reverse wired condition, processor  56  sends a signal to SCR  40  to turn ON, causing circuit interrupter  24  to trip. If the reset button  46  is operated, circuit interrupter  24  momentarily resets, but trips soon thereafter when the miswired condition is again detected by processor  56 . The circuit interrupter will continue to trip until the reverse wiring condition is corrected. It is noted that device tripping is automatic, i.e., the installer does not have to manually operate the test facility or manually perform some other action to initiate lock-out. However, sensing current has been described as a prerequisite for determining proper or reverse wiring. Therefore the device will fail to lock-out, even if a miswired condition is present, until such time as a load ( 60 ,  62 ) is connected to the device to generate the current. It is desirable for device  10  to lock-out in response to a miswired condition without having to wait until an external load is connected. 
     In an alternate embodiment, device  10  may include an internal load  64  disposed between current transformer  54  and circuit interrupter  24 . Internal load  64  operates in a similar manner to external load  60  by generating a current flow having a polarity indicative of proper wiring. Unlike load  60 , load  64  does not generate a current flow through transformer  54  when device  10  is reverse wired. Thus, when device  10  includes an internal load, lock-out circuit  50  is configured to permit device  10  to reset when the current polarity and the voltage polarity match each other. On the other hand, lock-out circuit  50  is configured to trip device  10  when the current polarity and the voltage polarity oppose each other or when no load current is being sensed by transformer  54  (i.e., before device is connected to an external miswired load  60 ). 
     Alternatively, an internal load  66  may be disposed between current transformer  54  and the line terminals  12 , 14 . Load  66  operates in a similar manner to load  60  by generating a current flow through transformer  54  indicative of reverse wiring. Unlike load  60 , load  66  does not generate a current flow through transformer  54  when device  10  is properly wired. In this embodiment, lock-out circuit  50  is configured to trip device  10  when the current polarity through load  66  (with or without load  60 ) compared to the voltage polarity oppose each other. On the other hand, lock-out circuit  50  is configured to permit device  10  to reset when the current polarity and voltage polarity match each other, or when there is no load current present. In yet another embodiment of the present invention, loads  64  and  66  are both be included. This also avoids the need for an external load in order to determine whether the protective device has been properly wired. 
     Referring back to  FIG. 1 , a transistor  58  may be disposed between SCR  40  and processor  56 . Processor  56  pulses transistor  580 N at a predetermined repetition rate to initiate a current through solenoid  42 . However, while each pulse generates a current through solenoid  42 , the resulting energy in the solenoid is not enough to actuate trip mechanism  44 . Solenoid  42  functions as a pulsed load. Processor  50  is configured to determine whether or not device  10  is properly wired on the basis of the direction (polarity) of the pulsed current through solenoid  42  with respect to the voltage polarity. Processor may make a miswire determination on the basis of one or more pulses. 
     In another embodiment, solenoid  42  may be connected between current transformer  54  and circuit interrupter  24 . Alternatively, solenoid  42  may be connected between feed-through load terminals  16 ,  18  or receptacle load terminals  20 , 22 . In either case, transistor  58  pulses solenoid  42  in the manner previously described. Solenoid  42  again functions as a pulsed load. 
     In yet another embodiment, transistor  58  is configured to pulse resistors  64  or  66  into conduction (not shown.) In general, the benefit of pulsing the current through an internal load ( 64 ,  66 ,  42 ) is that a thermal dissipation rating of a load may be reduced by more than ten-fold. Accordingly, the load may be miniaturized. 
     In the embodiment shown in  FIG. 1 , an indicator  62  is coupled to processor  56 . Indicator  62  includes visible and/or audible indication of a miswired condition. Processor  56  may provide a repetitive signal to indicator  62 , in which case indicator  62  provides a blinking and/or beeping indication of a miswired condition. 
     While  FIG. 1  and  FIG. 2  are directed to ground fault detection circuitry, the present invention is equally applicable to other types of protective devices. Those of ordinary skill in the art will recognize that substantially all of the various types of protective devices include similar components for sensing, detecting and interrupting the circuit interrupting contacts in response to a particular fault condition. For example, the sensor in an arc fault circuit interrupter (AFCI) is similar to transformer  26  but is typically configured to sense load current instead of differential current and/or line voltage. An AFCI sensor may include at least one of a toroidal transformer, shunt or voltage divider. Further, the detector in the AFCI may be implemented as an integrated circuit similar in form factor to the detector  32 . The AFCI detector may also be configured to detect an arc fault condition on the basis of the frequency spectrum of the load current. Those of ordinary skill in the art will recognize that an arc fault may exhibit high frequency noise burst patterns. Once an arc fault condition has been detected, a signal is sent to SCR  40  to trip the device. 
     Referring to  FIG. 3 , a schematic diagram in accordance with a second embodiment of the present invention is disclosed. Miswire lock-out circuit  300  is similar to lock-out circuit  50  shown in  FIGS. 1 and 2 . The embodiment shown in  FIG. 3  includes a shunt sensor  302  coupled to processor  304 . The function of sensor  302  is similar to transformer  54 . Processor  304  is configured to determine the polarity of the load current using shunt sensor  302 . 
     As embodied herein and depicted in  FIG. 4 , a schematic diagram in accordance with a third embodiment of the present invention is disclosed. This embodiment does not include a separate load current polarity sensor per se. Instead, the protective device itself is configured to determine the polarity of the load current. In particular, miswire lock-out circuit  400  includes a switching device  402  coupled to processor  400  by way of transistor  406 . Switching device  402  is open or closed in response to a signal from processor  404 . In particular, switching device  402  is opened or closed in response to a signal from processor  404  by way of transistor  406 . When switching device  402  is open, currents through line hot conductor  12  and line neutral conductor  14  flow equally and oppositely through differential transformer  26 . Accordingly, the differential signal generated by transformer  26  is not indicative of a fault (or simulated fault) condition. However, when switching device  402  is closed, a portion of the load current flowing through one or the other conductor is diverted through the switching device. Since the currents in the two conductors are no longer equal, a fault signal is provided to detector  32 . Detector  32  provides an output load current signal to processor  404  on detector output line  37 . Processor  404  uses the output load current signal to determine the load current polarity. 
     It is also noted that transistor  406  may perform a function similar to that performed by transistor  58  in the embodiment depicted in  FIG. 1 . Transistor  58  provided a pulsed signal to solenoid  42 . In response, solenoid  42  was momentarily driven into conduction to provide a pulsed load current. Thus, the embodiment in  FIG. 4  provides several means for detecting miswire, or reverse wiring, conditions. 
     Device  10  is shown in  FIG. 4  as being reverse wired. When the AC (or DC) source voltage is positive during the time that switching device  402  is closed, the direction of the summed current through differential transformer  26  results in detector  32  providing a negative current polarity signal to processor  404 . Since the voltage and current polarities oppose each other, processor  404  provides a signal to SCR  40  to trip circuit interrupter  24 . Switching device  402  may be closed by processor  400  only during the negative half cycle intervals of the AC source voltage cycle. This avoids the possibility of detector output signal  36  causing false tripping since SCR  40  cannot turn ON during negative half cycles. 
       FIGS. 5A-5E  are timing diagrams illustrating the miswire protection functionality of the present invention. The waveforms are described using the references in  FIG. 1  but are applicable to other embodiments of the invention as well. The waveforms pertain to a protective device  10  that is reverse-wired and in the reset state, i.e., AC source voltage is connected to the device feed-through terminals  16 ,  18 . 
       FIG. 5A  is a diagrammatic representation of the load current  502 . AC source voltage is applied to device  10  at time  500 . Referring to  FIG. 5B , processor  56  generates a predetermined time delay interval  501  also commencing at time  500 . The miswire lock-out circuit is prevented from tripping even if there is a miswire condition, until delay interval  501  elapses. Time interval  501  is pre-programmed into processor  56  based on known transient noise properties. Transient noise  505  may be generated by the initial application of AC power to a device, or by the application of AC power after a power outage. Accordingly, time interval  501  is programmed into processor  56  to prevent transients  501  from initiating a false lockout of device  10 . Those of ordinary skill in the art will understand that interval  501  is less than about 1 second. 
       FIG. 5C  is a diagrammatic representation of the source voltage  503 . Note that AC source voltage  503  is out of phase with load current  502 , shown in  FIG. 5A . As noted previously, the out of phase condition represents the fact that the protective device has been reverse wired. Note also that AC source voltage  503  and load current  502  are out of phase by a phase shift amount  506 . Phase shift  506  represents the possibility of an inductive load shift that loads  64 ,  66 , or  42 , if provided, are unable to compensate for. 
     As shown in  FIG. 5D , processor  56  pulses a load into conduction during an interval  508 . As described above, the pulsing is performed to compare the polarities of the load current and source voltage. In the example provided by  FIG. 5 , the two signals are of opposite polarity. Thus, processor  56  determines that device  10  has been miswired. Processor  56  may be programmed such that interval(s)  508  occur only during the negative half cycles of the source voltage for the reasons provided above. 
     Note also that interval(s)  508  must not be allowed to coincide with intervals  506 . Despite the fact that device  10  is miswired, the load current and source voltage polarities match in these intervals because of the phase shift  506 . Processor  56  is programmed to delay the commencement of interval  508  by a time period  510  from the current zero crossing to avoid an erroneous wiring state indication by processor  56 . 
     Window interval  512  shown in  FIG. 5E  prevents the miswire detection circuit from causing false tripping. Window  512  is initiated at time  500  and elapses after a predetermined period of time has transpired. Thus, the proper wiring/miswiring decision-making process only occurs within window  512 . Once the miswire lock-out circuit  50  completes its task, it is prevented from causing false tripping after interval  512  has elapsed. 
     As embodied herein and depicted in  FIG. 6 , a schematic of a miswire lockout circuit in accordance with a fourth embodiment of the present invention is disclosed. Reference is made to U.S. patent application Ser. No. 10/884,304, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of a miswire circuit including a fuse. Miswire lock-out circuit  600  is connected to the line side of circuit interrupter  24 . When protective device  10  is installed, fuse  602  is closed. If the device is properly wired during the installation and the source voltage is turned on, current through the circuit  600  generates a simulated fault current to trip the circuit interrupter  24 . Current continues to flow through circuit  600  until a thermal element  604  disposed in circuit  600  opens fuse  602 , thus breaking electrical connectivity in the circuit. Once electrical connectivity is broken, the simulated fault current ceases, permitting device  10  to be reset. 
     Assuming the device is reset, if the device is miswired during the installation and the source voltage is turned on current flows through circuit  600  by way of circuit interrupter  24 . The simulated fault current causes the circuit interrupter  24  to trip. In turn, the fault current stops flowing by the tripping action. Note that the circuit interrupter trips in response to the simulated fault current typically in less than 25 milliseconds. The heat generated in thermal element  604  during this time frame is insufficient to open fuse  602 . Accordingly, fuse  602  is operational until the device is wired properly. Device  10  will continue to trip after each reset until the device is wired properly. 
     In an alternate embodiment, fuse  602  is configured to self-heat in response to the current flow, eliminating the need for thermal element  604 . Other miswire circuits are similar in performance to circuit  600  but are re-configured to produce a signal or simulated fault signal as appropriate for ground fault circuit interrupters, arc fault circuit interrupters, combination arc fault and ground fault circuit interrupters or other types of protective devices (not shown.) 
     Fuse  602  may also be implemented using a resettable, or reclosable, fuse. After device  10  is removed from an installation, fuse  602  is closed to thereby restore miswire circuit  600 . At this point, the protective device is configured to enter a lock-out state in the event of being miswired during re-installation. 
       FIGS. 7-11  illustrate a typical installation of the present invention. Referring to  FIG. 7 , a front cover view of a protective device in accordance with the present invention is disclosed. Device  10  includes a front housing  750  that includes a flange  752 . The protective device is configured to be covered by a wall plate  700  that is secured to device  10  by way of fasteners  702 . Alternatively, device  10  can be covered by a panel that is fastened to device  10  by way of fasteners  702 . Fasteners  702  cause wall plate  700  (or the panel) to be pressed against flange  752 . 
       FIG. 8  is a cross-sectional view of the protective device shown in  FIG. 7 . Device  10  includes a housing  754  that is configured to mate with the front housing  750 . A printed circuit board (PCB)  758  is disposed within device  10 . Resettable fuse  602  is coupled to PCB  758 . Resettable fuse  602  is reset by applying a momentary force to arm  603 . Note that wall plate  700 , or the panel, is not shown as being installed in  FIG. 8 . Thus, probe  756  to free to extend into the unoccupied region above flange  752  due to a biasing force of spring  760 . The biasing force of spring  760  also forces arm  603  against fuse  602 , urging the fuse to re-close. Accordingly, once the wall plate is removed, the fuse miswire circuit  600  is re-established. 
       FIG. 9  shows device  10  after re-installation. Wall plate  700  (or the panel) is pressed against flange  752  by way of fasteners  702  directing probe  756  in a downward direction. Probe  756  compresses spring  760  so that force is no longer being applied by arm  603 . As such, fuse  602  stays in the closed position until such time as device  10  has been properly wired. As a side benefit, if device  10  is installed, but the wall plate  700  has not been installed, fuse  602  is permanently closed. Thus circuit  600  prevents device  10  from resetting whether device  10  is properly wired or miswired. The rationale behind this safety feature is that without the wall plate, the load terminals are physically accessible to the user. Accordingly, the safety feature prevents the user from being exposed to any voltage present on the load terminals. 
     It will be apparent to those of ordinary skill in the pertinent art that modifications and variations can be made to resettable fuse  602  of the present invention depending on the form factor of PCB  758  and the disposition of arm  603 . By way of example, resettable fuse  602  may be implemented using Model X 2296 manufactured by Thermo-Disc. Of course, those of ordinary skill in the art will recognize that any suitable resettable fuse device may be employed in the present invention. 
       FIGS. 10-11  are cross-sectional views of the protective device in accordance with an alternate embodiment of the present invention. Probe  800  is similar to probe  756  except that it includes striker  802 . Striker  802  is configured to deflect cantilever beam  804  when wall plate  700  is installed. Once cantilever  804  is deflected by a predetermined amount, it clears striker  802  and rebounds to momentarily apply a force to arm  603  to re-close the fuse. Accordingly, miswire circuit  600  may be reactivated only by installation of the wall plate. In an alternate embodiment, a striker is configured so that the momentary force to arm  603  occurs when wall plate  700  is removed. For this embodiment, reactivation of the miswire circuit  600  does not require the installation of a wall plate, only the removal of a wall plate. 
     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.