Patent Application
20090262471
According to the National Fire Protection Association and the National Fire Incident Reporting System data, during the five-year period from 1994 to 1998, there were an average of 73,500 annual electrical fires that were responsible for 591 deaths, 2,247 injuries, and property damage totaling $1,047,900,000. A report by the National Association of State Fire Marshals states that of these 73,500 electrical fires, 60,900 or 82% were caused by arcing, not overloads or short circuits. Arcing is the phenomenon that occurs when the electrons of an electric current, often strong, brief, and luminous, jump across a gap. Unwanted arcs in electrical circuits can cause fires.
Starting in 2002, the National Electrical Code (NEC) requirements in article 210.12 state, “All branch circuits that supply 125-volt, single-phase, 15- and 20-ampere outlets installed in dwelling unit bedrooms shall be protected by an AFCI listed device to provide protection of the entire branch circuit.” This includes outlets for receptacles, lights, fans, and smoke detectors in circuits that supply bedrooms.
Indeed, although the 2002 NEC code required AFCI protection only in bedrooms, many state and local “authorities having jurisdiction” (AHJs) adopted more restrictive policies, requiring AFCIs in all living spaces of a home. Beginning January 2008, only “combination type” AFCIs will meet the NEC requirement. The 2008 NEC code requires installation of combination-type AFCIs in all 15- and 20-amp residential circuits with the exception of laundries, kitchens, bathrooms, and garage, and unfinished basements. The insurance industry was involved in this direction as one of the main preventative actions to reduce electrical fires. This will likely increase implementation of AFCI support to reduce nuisance tripping.
“Nuisance tripping” takes place when an AFCI generates a trip signal with no actual arcing taking place. Current dimming module behavior does not support AFCI breakers which can cause them to trip indefinitely. This may be due to several possibilities, one of which is that with no stipulation prohibiting the separation of lighting and general-use outlets with regard to the branch circuits that feed them, it is common practice to combine these loads within rooms. It is then possible and probable that a single load or group of loads exceeding 800 watts can be simultaneously activated from a control station, thus creating a nuisance trip of the corresponding AFCI breaker.
To the AFCI breaker, cold filaments in incandescent lamps appear as having a much lower resistance until they warm up and reach the designed higher resistance value. For example, this initial resistance may be about 1/10 of its ultimate designated higher resistance value. Standard light switches do not have this effect on an AFCI breaker due to the inherent contact bounce that occurs when a light switch is turned on. This contact bounce allows the filaments to be “pre-heated” if even for a millisecond, before presenting the full load to the breaker. Solid state dimmers, however, do not have the contact bounce, but rather present the entire cold filament load to the breaker, from zero to full-load-amps in less than two half cycles. Solid state dimmers routinely contribute to nuisance tripping when supplied by an AFCI, combined with the control of loads greater than 800 watts or more.
An AFCI opens the circuit for low-level line-to-neutral faults when three to eight half-cycles exceed 50 A peak (within 0.5 second), whereas a standard circuit breaker might not open for many hundreds of half-cycles. The arc fault detection circuit includes a controller which produces a trip signal in response to a determination that an arcing fault is present in the electrical circuit, and an inhibit/blocking function for preventing the production of the trip signal under one or more predetermined conditions.
The following implementations and aspects thereof are described and illustrated in conjunction with systems, which are meant to be exemplary and illustrative, not limiting in scope. In various implementations, one or more of the above-described issues have been reduced or eliminated, while other implementations are directed to other improvements.
In view of the foregoing it is a general aspect of the presently described developments to provide for a support system for an Arc Fault Circuit Interrupter; by including functionalities and/or devices for providing for a delay between each load to prevent the cumulative wattage from creating a nuisance AFCI breaker trip, or by providing a number of pre-heat pulses prior to applying the full current to the load.
The foregoing specific aspects and advantages of the present developments are illustrative of those which can be achieved by these developments and are not intended to be exhaustive or limiting of the possible advantages which can be realized. Thus, those and other aspects and advantages of these developments will be apparent from the description herein or can be learned from practicing the disclosure hereof, both as embodied herein or as modified in view of any variations which may be apparent to those skilled in the art. Thus, in addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to and by study of the following descriptions.
In the drawings:
Described here is an Arc Fault Circuit Interrupter (AFCI) Support to eliminate nuisance tripping caused by solid state dimmers. Through unique firmware and software enhancements, here referred to as “AFCI Support,” reliable control can be had of incandescent lighting loads greater than 800 watts with little or no nuisance tripping of AFCI breakers that supply them, by using two different methods hereinafter referred to as Level One Support and Level Two Support.
In Level One Support, individual loads, arranged in scenes or groups, which when activated together, form an accumulated total of 800 watts or more, can hereby be “sequenced” with a delay, e.g., a 1 millisecond delay, between each load to prevent the cumulative wattage from creating a nuisance AFCI breaker trip.
In Level Two Support, loads with individual wattages of 800 watts or more can be provided with a number, e.g., two, “pre-heat” pulses prior to applying the full current to the load. If there is more than one load of 800 watts or more being activated, each load may receive a pulse, as well as being sequenced with a delay (e.g., the millisecond delay of Level One Support) between each individual load.
Moreover, an alternative may be to let in some high level current (or high RMS value, i.e. the effective value of a varying current) for a short period, e.g., a short number of seconds. Such high level current might be more or less than that needed for regular operation. Another alternative may be to provide something less than full power initially to moderate the value, and/or may be to step up the power over time, and/or to step up the value of two or more different “pre-heat” pulses. For example, perhaps a quarter power pulse or step followed by a half power step or pulse, and/or in some cases one or the other or both of the previous followed by a three-quarters power step or pulse. These are exemplar values only, other greater or lesser values may be uses at any of these points.
Still furthermore, an application hereof may be described in the following manner. The length or level of a particular one or more pulses, whether referred to as “pre-heat” pulses or otherwise, e.g., rather as delays; may be tuned to or for the particular load. For example, some possible alternative lighting “loads” may include halogen, quartz, incandescent or fluorescent, inter alia. Each of these may, however, present a different in-rush current need relative to the AFCI. For example it has been found that a tuned cycle for a pulse hereunder for a halogen light load may be about half that used for a quartz light load; thus, if as it has been found, a halogen light load may use a 1.5 cycle pulse, a quartz light load might use a 3 cycle pulse according hereto. Other numbers or cycles may be used depending upon the load.
However, the present development may take these different references and “program” or provide for them to be programmed according to end-user desire. For example, an end-user can use a system hereof (hardware, firmware or software, or any combination thereof) to “program” for the particular “load” to be used. Indeed, the system may only require input of the particular minimum information of, for example, whether an AFCI is being used, and then what type of light “load” is being used, whether halogen, quartz, incandescent or fluorescent, inter alia. Then, the system may provide for the pre-selected pulse for that load. A system hereof could thus be used with one or a plurality of zones, each zone potentially having different types of “loads”; and the system providing the appropriate pulse length or level (one quarter, one half, or three quarters or some other percentage of total).
An exemplar implementation will now be set forth.
The example given herein uses a dimming module. Dimming module firmware can be modified according hereto to understand a new arc fault flag that in this example can have one of 3 possible states to determine the turn on behavior.
The first state, State 1, may be a default state. State 1 involves no new behavior, but rather may turn on lights using current dimming behavior. State 2, also known as arc fault level 1, may involve some millisecond between turning on each dimmer leg. No pulsing is necessarily required during this State 2. State 3, also known as arc fault level 2, may involve some millisecond delay between turning on each dimmer leg. All legs may be pulsed twice to warm up the load.
Dimming module setup may include the following steps. The user may be prompted to specify one of the following, for example: a 15 amp breaker, a 20 amp breaker, a 15 amp arc fault breaker or a 20 amp arc fault breaker.
A dimming module may be entered into a floor plan by drag and drop in programming the floor plan. As illustrated in
In
As illustrated in
When a dimming module is wired to a breaker box, the breaker box may be set to inherit the amp and arc fault properties. As shown in
The builder programming support may determine the appropriate state for each dimming module script based on the breaker and load wattages. Table 1 provides examples of the scripts to be run in particular amp and total wattage situations.
This application claims the benefit of priority under 35 U.S.C. § 119(e) from U.S. Provisional Patent Application No. 61/046,321, entitled “Arc Fault Circuit Interrupter (AFCI) Support”, filed Apr. 18, 2008; U.S. Provisional Patent Application No. 61/046,381, entitled “Arc Fault Circuit Interrupter (AFCI) Support”, filed Apr. 18, 2008; and U.S. Provisional Patent Application No. 61/046,435, entitled “Arc Fault Circuit Interrupter (AFCI) Support”, filed Apr. 20, 2008, all of which are incorporated herein in their entirety by this reference.
| Number | Date | Country | |
|---|---|---|---|
| 61046321 | Apr 2008 | US | |
| 61046381 | Apr 2008 | US | |
| 61046435 | Apr 2008 | US |
