Abstract:
The present invention is directed to an electrical wiring protection device that includes a housing assembly having a hot line terminal, a neutral line terminal, a hot load terminal, and a neutral load terminal partially disposed therein. A miswire detection circuit is coupled to the hot line terminal, the neutral line terminal, the hot load terminal, and the neutral load terminal. The miswire detection circuit is configured to generate a miswire fault condition when AC power is coupled to the hot load terminal and the neutral load terminal and open circuit when AC power is coupled to the hot line terminal and neutral line terminal. A fault detection circuit is coupled to the miswire detection circuit. The fault detection circuit is configured to generate a fault detection signal in response to detecting at least one fault condition. The at least one fault condition including the miswire fault condition. An interrupting contact assembly is connected to the fault detection circuit. The interrupting contact assembly includes interrupting contacts that provide electrical continuity between the hot line terminal and the hot load terminal, and the neutral line terminal and the neutral load terminal in a reset condition. The interrupting contact assembly is also configured to open the interrupting contacts in response to receiving the fault detection signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This 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 Ser. No. 09/718,003 now U.S. Pat. No. 6,522,510 filed Nov. 21, 2000, the content 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. 

   FIELD OF THE INVENTION 
   This invention pertains to the field of ground fault circuit interrupter devices, and in particular, to a ground fault interrupter device with an indicator lamp and protective circuit powered from the hot bus bar of the interrupting contacts. 
   BACKGROUND OF THE INVENTION 
   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. 
   SUMMARY OF THE INVENTION 
   Briefly stated, an AC power line protection device which includes a protection circuit which guards against miswiring also has an indicator lamp which lights when the device is in the tripped condition and turns off when the device is reset. If the device is miswired after having been wired properly, the indicator lamp does not light when the device is tripped, and so provides a supplemental indication of miswiring. The protection circuit is powered from the hot line bus bar. The indicator lamp is also powered via the hot line bus bar of the interrupting contacts to meet safety standards. 
   One aspect of the present invention is directed to an electrical wiring protection device that includes a housing assembly having a hot line terminal, a neutral line terminal, a hot load terminal, and a neutral load terminal partially disposed therein. A miswire detection circuit is coupled to the hot line terminal, the neutral line terminal, the hot load terminal, and the neutral load terminal. The miswire detection circuit is configured to generate a miswire fault condition when AC power is coupled to the hot load terminal and the neutral load terminal and open circuit when AC power is coupled to the hot line terminal and neutral line terminal. A fault detection circuit is coupled to the miswire detection circuit. The fault detection circuit is configured to generate a fault detection signal in response to detecting at least one fault condition. The at least one fault condition including the miswire fault condition. An interrupting contact assembly is connected to the fault detection circuit. The interrupting contact assembly includes interrupting contacts that provide electrical continuity between the hot line terminal and the hot load terminal, and the neutral line terminal and the neutral load terminal in a reset condition. The interrupting contact assembly is also configured to open the interrupting contacts in response to receiving the fault detection signal. 
   In another aspect, the present invention includes a method for detecting a miswire condition in an electric circuit. The method includes coupling a protection device to the electric circuit. The protection device includes a housing assembly including a hot line terminal, a neutral line terminal, a hot load terminal, and a neutral load terminal partially disposed therein. Interrupting contacts are configured to provide electrical continuity between the hot line terminal and the hot load terminal, and the neutral line terminal and the neutral load terminal in a reset condition and trip in response to receiving a fault detection signal, whereby the electrical continuity between the hot line terminal and the hot load terminal, and the neutral line terminal and the neutral load terminal is interrupted. The method also includes the step of detecting a miswire condition when the AC power is coupled to the hot load terminal and the neutral load terminal. A fault detection signal is generated in response to the step of detecting a miswire condition when the AC power is coupled to the hot load terminal and the neutral load terminal. The interrupting contacts are tripped in response to the fault detection signal, whereby the electrical continuity between the hot line terminal and the hot load terminal, and the neutral line terminal and the neutral load terminal is interrupted. The interrupting contacts are reset to restore electrical continuity between the hot line terminal and the hot load terminal, and the neutral line terminal and the neutral load terminal. The steps of detecting, generating, and tripping are repeated if the AC power is coupled to the hot load terminal and the neutral load terminal. 
   In another aspect, the present invention includes an electrical wiring protection device that includes a housing assembly including a hot line terminal, a neutral line terminal, a hot load terminal, and a neutral load terminal partially disposed therein. A fault detection circuit is coupled to the hot line terminal, the neutral line terminal, the hot load terminal, and the neutral load terminal. The fault detection circuit is configured to generate a fault detection signal in response to detecting at least one fault condition. An interrupting contact assembly is connected to the fault detection circuit. The interrupting contact assembly includes interrupting contacts that provide electrical continuity between the hot line terminal and the hot load terminal, and the neutral line terminal and the neutral load terminal in a reset condition. The interrupting contact assembly is configured to open the interrupting contacts in response to receiving the fault detection signal. An indicator circuit is coupled to the interrupting contact assembly and the fault detection circuit. The indicator circuit is configured to indicate a trip condition, a miswire condition, and an end-of-life condition. 
   In another aspect, the present invention includes an electrical wiring protection device that includes a housing assembly including a hot line terminal, a neutral line terminal, a hot load terminal, and a neutral load terminal partially disposed therein. A miswire detection circuit is coupled to the hot line terminal, the neutral line terminal, the hot load terminal, and the neutral load terminal. The miswire detection circuit is configured to generate a miswire fault condition when AC power is coupled to the hot load terminal and the neutral load terminal and open circuit when AC power is coupled to the hot line terminal and neutral line terminal. A fault detection circuit is coupled to the miswire detection circuit. The fault detection circuit is configured to generate a fault detection signal in response to detecting at least one fault condition. The at least one fault condition includes the miswire fault condition. An interrupting contact assembly is connected to the fault detection circuit. The interrupting contact assembly includes interrupting contacts that provide electrical continuity between the hot line terminal and the hot load terminal, and the neutral line terminal and the neutral load terminal in a reset condition. The interrupting contact assembly is configured to open the interrupting contacts in response to receiving the fault detection signal. An indicator circuit is coupled to the interrupting contact assembly and the fault detection circuit. The indicator circuit is configured to indicate a trip condition, a miswire condition, and an end-of-life condition. 
   In yet another aspect, the present invention includes a method for manufacturing an electrical wiring device. The method includes assembling the electrical wiring device. The electrical wiring device includes a housing assembly including a hot line terminal, a neutral line terminal, a hot load terminal, and a neutral load terminal partially disposed therein. A miswire detection circuit is coupled to the hot line terminal, the neutral line terminal, the hot load terminal, and the neutral load terminal. The miswire detection circuit includes a switch configured to disable the miswire detection circuit in an open state. The miswire detection circuit is configured to generate a miswire fault condition when the switch is in a closed state. The miswire fault condition is generated when AC power is coupled to the hot load terminal and the neutral load terminal and open circuit when AC power is coupled to the hot line terminal and neutral line terminal. A fault detection circuit is coupled to the miswire detection circuit. The fault detection circuit is configured to generate a fault detection signal in response to detecting at least one fault condition. The at least one fault condition includes the miswire fault condition. Interrupting contacts are configured to provide electrical continuity between the hot line terminal and the hot load terminal, and the neutral line terminal and the neutral load terminal in a reset condition and trip in response to receiving a fault detection signal, whereby the electrical continuity between the hot line terminal and the hot load terminal, and the neutral line terminal and the neutral load terminal is interrupted. The method also includes the step of opening the switch to thereby disable the miswire detection circuit. At least one test is performed on the electrical wiring device. The switch is closed to thereby enable the miswire detection circuit. 
   In yet another aspect, the present invention includes an electrical wiring device that includes a housing assembly having line terminals and load terminals partially disposed therein. A fault detection circuit is coupled to the line terminals and/or the load terminals. The fault detection circuit is configured to generate a fault detection signal in response to detecting at least one fault condition. A wiring detection circuit is coupled to the line terminals and/or the load terminals. The wiring detection circuit includes at least one electrical component in series with a switch. The at least one electrical component is coupled to a control input of a silicon controlled rectifier. The wiring detection circuit is configured to propagate a current signal through the at least one electrical component when the switch is closed and power is applied to the line terminals. An interrupting contact assembly is connected to the fault detection circuit and the wiring detection circuit. The interrupting contact assembly includes interrupting contacts configured to provide electrical continuity between the line terminals and the load terminals in a closed state and open the interrupting contacts in response to receiving the fault detection signal. The interrupting contact assembly is in the open state absent the current signal flowing through the at least one electrical component. 
   In yet another aspect, the present invention includes an electrical wiring device that includes a housing assembly including line terminals and load terminals partially disposed therein. At least one detection circuit is coupled to the line terminals and/or the load terminals. The at least one detection circuit is configured to generate a signal in response to detecting a correct wiring condition. An interrupting contact assembly is coupled to the at least one detection circuit. The interrupting contact assembly includes interrupting contacts that are configured to provide electrical continuity between the line terminals and the load terminals in a closed state and interrupt the electrical continuity in an open state. The interrupting contact assembly is in the open state absent the signal being provided by the at least one detection circuit. 
   In yet another aspect, the present invention includes an electrical wiring device that includes a housing assembly including line terminals and load terminals partially disposed therein. An interrupting contact assembly is coupled to the line terminals and the load terminals. The interrupting contact assembly includes a trip solenoid coupled to interrupting contacts. The interrupting contacts are configured to provide electrical continuity between the line terminals and the load terminals in a reset state and interrupt the electrical continuity in an open state. At least one detection circuit is configured to detect power coupled to the line terminals. The detection circuit permits the interrupting contacts to be driven into the reset state without an enabling signal being received from the trip solenoid. 
   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  shows a schematic of a GFCI circuit with miswire protection and an indicator lamp according to an embodiment of the invention. 
       FIG. 2  shows a schematic of a lockout configuration according to an embodiment of the invention. 
       FIG. 3  shows a schematic of an alternative lockout configuration according to an embodiment of the invention. 
       FIG. 4  shows a schematic of a protective circuit with miswire protection and an indicator lamp according to an embodiment of the invention. 
       FIG. 5  shows a schematic of a protective circuit with miswire protection and an indicator lamp according to an embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , a GFCI circuit is shown generally at  100 . When a differential transformer L 1  senses unequal amounts of current flowing in the hot and neutral conductors due to a ground fault condition, circuit  100  causes a breaker coil  110  to activate, opening circuit interrupting mechanism  120 . Circuit interrupting mechanism  120  conventionally includes hot and neutral bus bars  502 ,  504  that make and break contact with the hot and neutral power lines, respectively, via contacts located on both the bus bars and power lines at the four contact points. A test button  130  induces a simulated ground fault when pushed in and causes breaker coil  110  to activate. 
   This improved GFCI contains two unique features that address the problems noted in the background section. The first is a miswire circuit which uses a fault resistance R 10 , R 13  creating a differential current on the primary of the differential current transformer L 1  that exceeds the level of differential current that the GFCI has been designed to interrupt, typically 6 milliamperes. The fault resistance R 10 , $13 is on the line side of interrupting contacts  120  electrically located between the line and load terminals of the hot and neutral wire paths. The ground fault circuit sensing electronics of GFCI circuit  100  derives power from the line side terminals of the GFCI. 
   Should the GFCI be wired in a mode where power is supplied to the load terminals, i.e., miswired, if the GFCI is tripped, nothing visible happens. If the GFCI is in the reset condition, it will immediately trip when powered. In this mode, the current flowing through the fault resistance R 10 , R 13 , derived from the line terminal side of the device, is interrupted when the device trips. 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 300 ms. Because the trip time of the GFCI is less than or equal to 25 ms, fault resistors R 10 , R 13  do not have enough time to clear. If one attempts to reset the device when in the miswired condition, the device immediately trips out again, and this continues until such time as the device is wired correctly, that is, when power is applied to the GFCI at the line terminals. This effectively results in a GFCI that will not operate, i.e., be able to be reset, until such time as the device is properly wired. 
   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. This can be accomplished by selecting a resistor or resistors whose power rating is greatly exceeded by the current, such that the resistor or resistors open. Another option is to provide a fuse (F 1  in  FIG. 3 ) in series with the fault resistance R 10 , R 13  with a properly selected I 2 t rating so that the fuse blows instead of the fault resistance R 10 , R 13 . The term “resistive element” as used herein refers to either a resistance or a fuse. Once the device has been properly wired with power connected to the line terminals and the fault has been cleared, the device can be reset and provide its normal protective functions. 
   Two interesting issues with this miswire protection concept are how to perform the Underwriters Laboratories Standard 943 required tests during manufacturing of the protective device without the differential current produced by the fault resistor affecting the test results, or causing the fault resistor to clear in the manner previously described. A solution is to place a normally closed switch S 1  in series with the fault resistance R 10 , R 13  previously described as producing the differential current. This switch S 1  is preferably a flexible conductive spring arm that normally rests against a contact on the top side of the printed circuit board. Directly below the spring arm of switch S 1  is a hole in the printed circuit board, and below this hole is another hole in the plastic back body of the GFCI device. When the GFCI is loaded into a piece of test equipment designed to perform the required manufacturing tests, a mechanical test probe engages the spring arm of switch S 1  through the two aforementioned holes, causing the spring arm of switch S 1  to be pushed away from the contact and therefore opening the differential current circuit path. Manufacturing testing can now be performed without any circuit effect from this path, without burning out fault resistance R 10 , R 13 . The last test performed on the GFCI device in the test sequence is to disengage the probe from the spring arm of switch S 1 , which reconnects the differential current circuit path. Line voltage is then applied to the load contacts. The differential current causes the GFCI to trip, thereby checking the integrity of the differential current circuit path and components. 
   The second feature of this improved GFCI is a light with multiple indication meanings. The circuit in  FIG. 1  includes resistors R 11 , R 12 , R 14 , and an indication device, shown on the schematic as neon light  140 . 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 works as follows. When the GFCI is wired properly, a 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. 
   Referring to  FIG. 2 , an embodiment of the invention is shown at  200  in which the protection device cannot be rest if the SCR shorts out, i.e., the device is “locked out.” This is because breaker coil  110  draws its power from the load sides of contacts  120  instead of the line side as in the embodiment of  FIG. 1 . When the SCR shorts out, breaker coil  110  immediately trips and opens contacts  120 . Opening contacts  120  breaks the current to the load side of the device, so breaker coil  110  is de-energized, preventing it from burning out. When attempting to reset the device, breaker coil  110  immediately trips out contacts  120 , thus preventing the device from being reset. Since the device cannot be reset, resistor R 14  is not used in this embodiment because there is no need to indicate via light  140  that the device has a faulty SCR; the inability to reset the device signals that condition. 
   Referring to  FIG. 3 , an alternative lock-out embodiment is shown at  300  which shows the series combination of light  140  and resistor R 12  connected in parallel to the neutral conductor contact instead of the hot conductor contact as is the case in  FIGS. 1 and 2 . A resistor R 15  completes the light circuit from load neutral to line hot. The miswire circuit fault resistance is shown here as resistors R 16 , R 17 , and R 18  in series with fuse F 1 . This embodiment eliminates any trickle current that might be flowing if the device is miswired. 
   Referring to  FIG. 4 , an embodiment of the invention is shown at  400  in which the protection device can be reset if the SCR shorts out. The embodiment is similar to the one shown in  FIG. 1  except that it is generalized to apply to different protective devices such as ground fault circuit interrupters (GFCI&#39;s) or devices intended to interrupt ground faults from personnel contact with a power line conductor, arc fault circuit interrupters (AFCI&#39;s) 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. 
   According to this embodiment, the protective devices mentioned have a protective circuit  402  that detects the respective fault condition, turning on an electronic switching device such as SCR  404 , energizing a solenoid  406  coil which receives power from the line conductors, to open interrupting contacts  408 . Resistors R 11 , R 12 , R 14 , fault resistors R 10 , R 13 , normally closed switch S 1 , fuse F 1 , and light  140  have the same functions as previously described in the above embodiments. When power is miswired to the load terminals and the protective device is reset such that interrupting contacts  408  are closed, current flows are 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. 
   There are several problems with the above embodiments from a regulatory and safety viewpoint. For example, there is a high voltage dielectric test requirement in the present UL Standard. This test is performed by applying a high voltage potential between line hot and load hot (and again between line neutral and load neutral) with the GFCI in the tripped condition. The light indication circuit connection between line and load hot in the previous embodiments would cause this test to fail. Another problem is that the circuit is subject to a maximum “leakage” current of 0.5 ma. This maximum allowable current is not sufficient to drive an LED to achieve the desired light output in the indicator light. A further problem is that the mechanical embodiment of the GFCI is subjected to a reset button “tease” test if the circuit power is derived from the load side contacts. The test is performed by placing an ohmmeter across each set of contacts and then slowly releasing the reset button during the rest sequence to see if there is a point at which one contact closes while the other remains open. The required mechanical structure to pass the tease test must be kept in mind when designing the electrical circuit portion of the protection device. These problems are solved by the next embodiment. 
   Referring to  FIG. 5 , a circuit  500  is shown in which circuit power is derived from hot bus bar  502  of the tripping mechanism. Circuit  500  still meets the original circuit requirements of removing power to the SCR when the SCR shorts. When power is applied and the GFCI is in the reset condition, bus bar  502  is in contact with the line hot, so the circuit is powered. When a ground fault is senses by differential transformer L 1 , the GFCI device of this embodiment trips normally. 
   Another function of the original circuit was to have an indicator light that came on as a result of the GFCI tripping when the GFCI was correctly wired, but when the GFCI was miswired by bringing power to the load contacts, the indicator light would not energize when the GFCI was tripped. The indicator circuit of this embodiment includes a diode D 2  in series with resistors R 20 , R 21 , R 22 , and R 23 , and an LED. When the properly wired GFCI trips and the SCR is not shorted out, bus bar  502  which provides power to circuit  500  is removed from contact with line hot. Current then flows through the indicator circuit, coil  110 , diode D 1 , and resistors R 6 , R 7 , R 8  to provide the power to illuminate the LED. Nominal current through the LED is about 4 ma. 
   The indicator circuit works in conjunction with the GFCI sense circuitry to power the indicator and to protect coil  110  in the event that the SCR shorts out. When the properly wired GFCI trips due to the SCR shorting, current still flows through the indicator circuit, coil  110 , and then through the shorted SCR. Nominal current in this scenario is about 10 ma. Coil  110  is protected from burning out by the resistor chain R 20 , R 21 , R 22 , and R 23 . Diode D 1  serves to half wave rectify the voltage for circuit  500 , protects the LED from breaking over in the reverse direction when the GFCI is tripped, and halves the power across resistor chain R 20 , R 21 , R 22 , and R 23  when the SCR shorts out. 
   When the GFCI is miswired, i.e., when the power is applied to the load terminals of the device instead of the line terminals of the device, the LED cannot light because there is no path for the current to take when the device is tripped. Thus, if the device is tripped and no light appears, the installer knows that the device is miswired. 
   Although the invention is described with respect to a GFCI, the invention is equally applicable to an AFCI or indeed to any circuit interrupting device. 
   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.