+ RSS FEED
Ever wondered what kind of receptacle is in your kitchen, bathroom, or garage and how it works? Or why your electrician had to put in new breakers in your panel? GFCI and AFCI protection are now integral parts of the NEC. In a residence, almost every outlet has to be protected by one or the other. The following is an interesting article from the IAEI magazine which discusses how these protective devices work, and why they are needed. Enjoy!
GFCI and AFCI protection have both become fundamental safety devices in electrical systems. Understanding the basics of ground-fault protection for people, and arc-fault protection for 15- and 20-amp branch circuits in dwelling units can ensure that your installations are code-compliant and help you in troubleshooting a circuit. As of the time this article was written (late January 2012), the NFPA code-making panels have met to consider proposals for the 2014 NEC. While the 2014 NEC code development process still has a long way to go, a number of GFCI and AFCI proposals are in the works, once again revising where these devices get installed. We’ll discuss a few of them along with some product standard and technology changes.
What is a GFCI?
Do you feel like you have a full understanding of how ground-fault protection works? If not don’t worry about it; we hope this discussion with help you and your co-workers further understand the basics.
There are two different types of ground-fault protection required in the NEC, ground-fault protection for people and ground-fault protection of equipment. Both work in a similar manner, but the protection levels are quite different. We will focus on ground-fault protection for people, provided by a device called a ground-fault circuit interrupter (GFCI). Article 100 in the NEC includes a definition for GFCIs.
Ground-Fault Circuit Interrupter (GFCI). A device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds the values established for a Class A device.
Informational Note: Class A ground-fault circuit interrupters trip when the current to ground is 6 mA or higher and do not trip when the current to ground is less than 4 mA. For further information, see UL 943, Standard for Ground-Fault Circuit Interrupters.
The Informational Note describes two very important performance criteria for GFCIs, namely that they will not trip if the leakage current to ground is less than 4 mA and will definitely trip if the leakage current is 6 mA or higher. The 4 mA level is necessary to prevent unwanted tripping due to the natural leakage in appliances, tools and other connected loads, and in the wiring itself.
The 6 mA must-trip level is important due to the amount of electrical current a human body can withstand without serious physical harm. Although physical effects will vary from person to person depending on whether they are male or female, an adult or a child, in general people will be able to sense electrical currents as low as 1 mA. At about 10 mA they may not be able to “let go” if they come into contact with an energized conductor. Current flow as low as 30 mA may cause breathing difficulty and heart fibrillation in small children. Fibrillation is almost certain for currents in the 100–200 mA range and current over 4 A will cause heart paralysis and tissue burning (see figure 1).
The ANSI/UL 943 standard defines the requirements for GFCI performance in the U.S. and is a tri-national standard, meaning that it is harmonized with CSA C22.2 No. 144.1 in Canada and ANCE NMX-J-520 in Mexico.
How does a GFCI work?
Figure 2. If there is an imbalance, an electronic circuit will determine if the leakage is enough to necessitate an interruption of the current flow.
The operation of a GFCI is really quite simple. It compares the amount of current going out to the load with the amount of current coming back from the load. In a single-phase device both the hot and neutral conductors pass through a current transformer (CT). This is why the load neutral conductor must be connected to a GFCI circuit breaker. If the current going out to the load equals the current coming back, there is no leakage to ground and the output from the CT is zero, but if there is an imbalance, an electronic circuit will determine if the leakage is enough to necessitate an interruption of the current flow, see figure 2.
In a two-pole GFCI circuit breaker, if single-phase (120 V) loads are to be served, both of the hot conductors, and the neutral conductor, must pass through the CT; therefore, the load neutral conductor must be connected to the circuit breaker, see figure 3. Three-pole (three-phase) GFCI circuit breakers are only suitable for protection of a three-phase load; hence, only the three-phase conductors must pass through the CT.
The white “pigtail” wire on a GFCI circuit breaker serves two functions. It completes the connection to the panel neutral bar for the neutral load conductor and also completes the power supply circuit for the electronics. This means that even in installations where there is no load neutral conductor, the white pigtail wire must still be connected to the neutral bar in the load center or panelboard in order for the electronic ground-fault protection circuit to function. (Note: Some manufacturers may offer circuit-breaker GFCIs with a plug-on neutral connection rather than a pigtail.)
What different types of GFCIs are available?
GFCIs are available in two different forms, circuit breakers and receptacles. Circuit-breaker GFCIs are dual listed as UL 489 circuit breakers and UL 943 ground-fault circuit interrupters, see figure 4. Receptacle-type GFCIs are listed as UL 943 ground-fault circuit-interrupter receptacles. The receptacle portion of the device must meet the requirements of UL 498.
In circuit breakers, the main circuit breaker contact(s) perform the interruption task when a ground-fault of sufficient magnitude is detected. In receptacles, a set of contacts performs the interruption task.
The terminals of circuit-breaker GFCIs are marked “Line” and “Load,” so they are not suitable for backfeeding. The terminals of receptacle-type GFCIs are similarly marked to insure that when properly wired the GFCI will also protect downstream receptacles should the installation so require.
Where are GFCIs required?
Figure 3. In a two-pole GFCI circuit breaker, if single-phase (120 V) loads are to be served, both of the hot conductors, and the neutral conductor, must pass through the CT; therefore, the load neutral conductor must be connected to the circuit breaker.
The NEC and Canadian Electrical Code (CEC) require GFCI protection in a large number of applications. The fundamental GFCI requirements are found in Section 210.8 of the NEC, although many other sections require them as well. Suffice it to say wherever electricity may be supplied in a potentially wet location, such as kitchen countertops, near sinks or outdoors, there is a good chance that GFCI protection is required there. A key revision to the 2011 NEC introduced a requirement for GFCIs to be readily accessible for monthly testing. Make sure you keep those receptacles located so as to not create an issue with this new requirement. If you are using a GFCI circuit breaker installed in a panelboard, this revised language is a nonissue.
What’s on the horizon for GFCI Protection?
A proposal to add an auto-monitoring function to the UL 943 GFCI standard is currently being considered by the industry. If adopted, this proposal will require that a GFCI be able to test itself, with the exception of the contact opening function. If a failure is detected, the GFCI will open the contacts (if possible) and deny power to the load. This new function was requested by the US Consumer Products Safety Commission because too few people regularly test their GFCIs. But even with auto-monitoring, users will still need to periodically test their GFCIs to insure that the contact opening function continues to work properly.
What is an AFCI?
Article 100 in the NEC includes a definition for AFCIs.
Arc-Fault Circuit Interrupter (AFCI). A device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.
The ANSI/UL 1699 standard defines the requirements for AFCI performance in the U.S. While CSA does certify AFCIs, a CSA standard has yet to be approved.
How does an AFCI work?
The operation of an AFCI is far more complex than that of a GFCI. Note that the NEC Article 100 definition states that an AFCI recognizes characteristics that are unique to arcing. Unfortunately, there is no single characteristic that is unique to hazardous arcs, so an AFCI must look for multiple characteristics, usually occurring at the same time or within a short period of time, to determine whether or not to interrupt the current flow. This usually involves monitoring both the current and the voltage.
We are using the term hazardous arcs in order to distinguish from operational arcs that naturally occur in an electrical system such as when switches or motors are operated. This greatly complicates the protection task. Not only must the AFCI detect whether arcing is taking place, but it must determine whether it is an operational arc or hazardous arc.
Because of this, the UL 1699 standard is unlike the GFCI or overcurrent protection device standards. In those standards, the device must operate when a specified level of current has been exceeded for a specified period of time. The UL 1699 standard, on the other hand, requires that various types and lengths of cable be intentionally damaged so as to create a hazardous arcing condition that must either be interrupted in a specified period of time or before a fire indicator is ignited.
Further, the UL 1699 standard requires that unwanted tripping tests be conducted using various loads that naturally arc or generate waveforms that might be mistaken for hazardous arcing. Masking tests are also conducted to insure that loads do not interfere with the ability of the AFCI to detect hazardous arcs.
Like in a GFCI, both the hot and neutral load conductors must be connected to the AFCI, and as is also the case with GFCIs, the white “pigtail” wire completes the connection to the panel neutral bar for the load neutral conductor which is terminated on the circuit breaker and also completes the power supply circuit for the electronics. (Note: Some manufacturers may offer AFCIs with a plug-on neutral connection rather than a pigtail.)
What different types of AFCIs are available?
AFCI circuit breakers of 15- and 20-amps are available for installation in load centers and panelboards. They are dual listed as UL 489 circuit breakers and UL 1699 arc-fault circuit interrupters (see figure 5).
Single-pole AFCI circuit breakers are available for 120-V branch circuit protection. Two-pole versions are also available from some manufacturers for the protection of 240 V loads (with common trip) or 120 V shared neutral loads (without common trip).
UL also lists AFCIs and leakage-current detector-interrupters (LCDIs) as a part of cord sets for use on appliances such as window air conditioners to meet the requirement in NEC 440.65.
While UL has a standard (UL 1699A) for outlet branch-circuit arc-fault circuit interrupters (OBC AFCI) and has listed one or two products, as of this writing none are commercially available.
In circuit breakers, the main circuit breaker contact(s) perform the interruption task when an arc fault is detected. In OBC AFCIs or cord-type AFCIs and LCDIs, a set of contacts performs the interruption task.
The terminals of circuit-breaker AFCIs are marked “Line” and “Load,” so they are not suitable for backfeeding.
When AFCI circuit breakers were first introduced, only the branch/feeder type was available. A branch/feeder type AFCI provides protection for parallel arc-faults that occur line-to-line or line-to-ground. The 2005 NEC required the use of combination-type AFCIs beginning January 1, 2008. Subsequent editions of the NEC have required the use of only combination-type AFCIs.
The UL 1699 standard requires that a combination-type AFCI provide protection against both parallel and series arc-faults. Series arc-faults are those that might occur due a break in a line or neutral conductor.
The certification label on the circuit breaker will identify if it is a branch/feeder or combination-type AFCI (see figure 3). The color of the test button is also a way to identify if a circuit breaker is a GFCI, branch/feeder or combination AFCI; however, as the standards do not define test button colors, each manufacturer has their own scheme for GFCI and AFCI test button colors.
Speaking of test buttons, it is important that users periodically test their AFCIs by pushing the test button.
Where are AFCIs required?
Section 210.12(A) of the 2011 NEC requires arc-fault protection of all 15- and 20-A 120-V branch circuits in dwelling unit “family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms or areas.” Section 550.25 requires AFCI protection in the same rooms in modular and mobile homes. An OBC AFCI may be installed at the first outlet in a branch circuit if a steel wiring method is used to protect the home run or if the home run is imbedded in at least 2 inches of concrete (see 210.12 Exceptions 1 and 2). Exception 3 allows AFCI protection to be omitted if a fire alarm circuit is encased in a steel wiring method.
Section 210.12(B) requires AFCI protection where a 15- or 20-A 120-V branch circuit “is modified, replaced, or extended.”
AFCIs and the 2014 NEC
A couple of key revisions to the NEC-2014 AFCI requirements are being considered by Code-Making Panel 2. The expansion of arc-fault protection to 15- and 20-A branch circuits serving kitchens and laundry rooms has been proposed. It is common to find AFCI protection on at least one of the kitchen branch circuits today when the dining area, which is required to have AFCI protection, is also serving the kitchen.
There is also consideration being given to permit a branch-circuit breaker to provide parallel arc-fault protection for a home run feeding an OBC AFCI installed in the first outlet without being enclosed in a steel wiring means or in concrete. A number of key conditions are essential for this protection system to work based on a recently issued UL research report:
The most significant challenge for this proposal may land in the lap of the contractor and electrical inspector. Will you be able to effectively meet and enforce these parameters? How will you know which circuit breaker has the appropriate instantaneous trip level? (Today, the instantaneous trip level of a branch-circuit breaker is not controlled by a standard and, therefore, can range well above the maximum 300-A level. Indeed, some applications require a higher trip level in order for the loads to operate.) The Code Panel rejected the fundamental requirement for a circuit breaker used in this application to have a Listed marking indicating suitability. How will you know the home run length? How will you know that the OBC AFCI was installed in the first outlet? You may want to review this proposal and provide your thoughts through an NEC comment to the Code Panel.
GFCIs and AFCIs continue to provide the protection envisioned by the electrical industry when they were first introduced in the 1960s and 1990s respectively. Here are a few items to consider as we wrap up this discussion:
Alan Manche Alan Manche is the director, Industry Standards for Schneider Electric / Square D. He is a licensed professional engineer in the state of Kentucky. He is a former member of NEC Code-Making Panel 8, served as a member of Code-Making Panels 10 and 20 during the development of the 2008 NEC and is currently a member of Code-Making Panel 10. He also currently serves as the chair of the technical committee for NFPA 70B – Electrical Equipment Maintenance, and serves on the NFPA 110 – Emergency and Standby Power Systems technical committee and on numerous UL product standard STPs. He has served as a product design engineer with responsibility for product certification of numerous Square D product lines including panelboards, switches, and busway. Alan also serves as a Schneider Electric liaison to the electrical inspection community, providing NEC educational programs across the country for inspectors and contractors.
Ed Larsen Ed Larsen is the manager, Industry Standards for circuit protection for Schneider Electric / Square D. He is responsible for managing company activities relating to product standards for overcurrent protective devices, including circuit breakers. Ed currently serves on NEC Code-Making Panel 11, is a member of the UL 1699 Standards Technical Panel and CSA C232(270) Technical Subcommittee for AFCIs and is chairman of the NEMA Personnel Protection Section (GFCIs). As an IEEE member, he authored a chapter in the Blue Book, the IEEE Recommended Practice for Applying Low-Voltage Circuit Breakers Used in Industrial and Commercial Power Systems and has presented papers on selective coordination and the safe application of arc-flash reduction systems. He has also authored articles in various trade journals. He is a member of several other UL, CSA, CANENA, IEEE and NEMA technical committees, the IAEI, IEEE Standards Association, Standards Engineering Society, and NFPA.
Tags: AFCI, AFCI breakers, AFCI protection, arc fault, GFCI, GFCI protection, GFI, GFI receptacles, Ground Fault, National Electric Code, NEC, Personnel protection, protection —
Below is an interesting article from the January 2011 IAEI magazine. Interesting basics of how electricity works. Enjoy!
By strict definition a material can be classified as either a conductor, an insulator, or a semiconductor based on its electrical properties. Before getting into the definition of each of these, a brief introduction to atomic theory is in order.
The atom is the smallest individual structure that makes up any chemical element while retaining properties of the element. The atom has a nucleus that contains protons and neutrons. Electrons orbit the nucleus at various distances and with varying amounts of energy. Protons are positively charged particles, electrons are negatively charged particles, and neutrons are uncharged particles. These electrons known as valence electrons are what we are primarily interested in from an electrical perspective. The valence shell is the outermost orbiting shell around the nucleus of the atom. It is important to note that electrons in the valence shell have higher energy than those orbiting closest to the nucleus. The distance away from the nucleus also allows these valence electrons to escape easier. The electrons that are given up from the valence shell become known as free electrons and contribute to current flow. Figure 1 shows the atomic structure of Hydrogen.
A conductor has the property of conducting electrical current very easily. Examples of conductors are gold, silver, copper, and aluminum. Gold and silver are not used as conductors in electrical construction because they are extremely cost prohibitive. Copper and aluminum are the traditional conductors used in electrical construction. These chemical elements are characterized by atoms that contain electrons in the valence shell that are not tightly bound and can easily contribute to current flow. Most conductors are metals and have high conductivities based on their resistivities.
An insulator has the property of not conducting electrical current very easily. Examples of insulators are glass, porcelain, rubber, and mica. Note how these products are not individual chemical elements but rather chemical compounds made up of different chemical elements. These chemical compounds are characterized by atoms that contain electrons in the valence shell that are tightly bound and do not easily contribute to current flow. Most insulators are non-metals and have low conductivities based on their resistivities.
A semiconductor has the property of behaving like something in-between an insulator and conductor. Examples of semiconductors are silicon and germanium. Silicon and germanium in elemental form are poor insulators and poor conductors. But when combined with other chemical compounds these devices can become insulators, conductors, or variations of both. Through a process known as doping, impurities are added to elemental silicon or germanium allowing the electrical properties of these materials to be changed.
So we have now learned that conductors can conduct current very easily, and insulators cannot conduct current very easily. What exactly is current and how does it flow through a conductor? To understand how current flows through a conductor we have to discuss four important terms: voltage, current, resistance, and resistivity.
The technical definition of voltage is the unit of potential difference between two points when 1 joule (unit of energy) of work is expended to move a test charge of 1 coulomb (unit of electric charge) from point A to point B. The unit of voltage is the volt and the meter used to measure voltage is the voltmeter. The voltmeter is placed in parallel with the device under test. Depending on whether the voltage representation is an AC or DC waveform, terms you will encounter are Average, RMS (root mean square), and P-P (peak to peak).
The technical definition of current is the movement of a test charge of 1 coulomb past a given point in 1 second. The unit of current is the ampere and the meter used to measure current is the ammeter. The ammeter is placed in series with the device under test.
The definition of resistance is the opposition to current flow that is measured when electric current flows through a conductor. The unit of resistance is the ohm and the meter used to measure resistance is the ohmmeter. A very useful equation known as Ohm’s Law is helpful in solving for the derived unit of resistance. See figure 2 for an example of Ohm’s Law.
Sometimes a mechanical analogy helps to keep these terms in perspective. Consider a garden hose that supplies the flow of water to a water fountain. The voltage would be the pressure of the water in the hose, the current would be the flow of water through the hose, and the resistance would be the friction the hose presents to the flow of water. The water fountain would be the load because it is performing some useful work.
The last term to define is resistivity. Resistivity is the resistance offered by a material to the flow of current designated by a specific length and specific cross-sectional area. The unit of resistivity is the circular mil-ohm/ft. One circular mil is the area of a circle having a diameter of 1 mil. One mil is 1/1000th of an inch. Copper is a conductor and therefore has a low resistivity and high conductivity. Rubber is an insulator and therefore has a high resistivity and low conductivity.
An example will help to clarify these points. Let’s take a #16 THHN copper conductor with a length of 100 ft. First recognize that the copper wire is a conductor and has a very low resistivity which means it will pass current very easily. Next recognize the THHN (thermoplastic insulation, high heat resistant, dry location only, nylon jacket) insulation is an insulator and has a very high resistivity which means it will not pass current very easily. From Table 8 Conductor Properties in Chapter 9 of the NEC, we find the diameter of #16 THHN to be 0.051 in. The resistivity of copper is 10.371 cmil-ohm/ft. Let’s calculate the resistance of 100 ft of this conductor.
L = 100 ft
Ρcu = 10.371 cmil − Ω ⁄ ft
D = 0.051 in = 51 mils
A = 2601 cmil
R (100 ft) = (ρ * (L)/A
= (10.371) * (100) / 2601
= 0.398 Ω
Voltage, current, resistance, and resistivity are important electrical units. Conductors and insulators are very common materials used every day in electrical construction. These core definitions will allow for further discussion of devices like resistors, capacitors, and inductors and how they perform in a variety of circuits and under a variety of conditions.
Tags: atom, conductor, electricity, resistance, volt, voltage —
Below is an interesting article in the IAEI magazine from July of 2009 highlighting key residential wiring code standards. It is interesting, as the author of the article points out, that residential wiring oftentimes is overlooked by many in our industry. As far as the state of Vermont is concerned, single family owner occupied residences do not have to be permitted or inspected, meaning anyone can perform wiring in residences that are not apartments. We feel that residential wiring safety is of the utmost importance. Our homes are where we spend the majority of our time, and where we and our families sleep, making it essential to make sure wiring is safe. Some standards have changed since the new 2011 version of the Electrical code has come out, however much having to do with residential wiring has stayed the same since the 2008 code (the major change concerns Arc Fault protection, please call us to learn about new requirements for this). This article should be very informative for homeowners looking to see whether or not their home wiring is safe and up to code. As always, we are more than happy to answer any questions on whether or not your home is up to current code standards Enjoy!
This article can be found at the following link:
A house is just a building…right?
The battle lines are drawn, you must choose a side! Somewhere along the way, it seems that we in the electrical industry have gotten off track a bit when it comes to Commercial vs. Residential applications. Why do some people and/or jurisdictions place more emphasis on their commercial electricians or inspectors than they do their residential counterparts? How did the notion get started that commercial applications are more important than residential applications? From this author’s standpoint, I don’t think one is more important than the other. It is interesting that the National Electrical Code includes more specific requirements for dwelling units than for any other type of occupancy. In this article, we will take a look at some of these specific requirements for dwelling units that would not be required in other type occupancies.
Receptacle Spacing Requirements
How many 125-volt general convenience receptacle outlets are required in that warehouse over there? How about the meeting room at the hotel we met in last week? Surely we are required to have several receptacle outlets in my office at work? The answer to all these questions is zero! In these non-dwelling unit occupancies, we’re not even required to have a receptacle outlet installed; much less, question how far apart can they be spaced. Yet, at a dwelling unit, we’re required to have no point along the floor line that is further than 1.8 m (6 ft) from a receptacle outlet. In other words, we could space receptacle outlets 3.7 m (12 ft) apart if we had a long enough wall.
Figure 1. Typical receptacle outlet spacing requirements for bedrooms, living rooms, etc., in dwelling units
Required receptacle outlets in dwelling units as specified in NEC 210.52 are those convenience receptacle outlets for circuits rated 125-volt, 15- and 20-amperes. This makes it clear that any receptacle outlets beyond those ampacity and voltage configurations are not permitted to be counted as the required receptacles for spacing, etc. For example, a 30-ampere, 240-volt receptacle outlet at a kitchen countertop location is considered over and above the required 125-volt, 20-ampere receptacle outlet required for that space.
The Code requires receptacle outlets for general use in every dwelling unit kitchen, family room, dining room, living room, parlor, library, den, sunroom, bedroom, recreation room, or similar room or area. The receptacle outlets are required to be installed so that no point along the floor line in any wall space is greater than 1.8 m (6 ft), measured horizontally, from an outlet in that space.
The Code describes wall space as: “A wall space 600 mm (2 ft) or more in width and unbroken along the floor line by doorways, fireplaces, and similar openings.” Every wall space of 600 mm (2 ft) or more in width is required to be treated individually and separately from all other wall spaces within the room. A wall space includes two or more walls of a room (around corners) where they are unbroken at the floor line [NEC 210.52(A)(2)(1)]. Spaces occupied by fixed panels in exterior or interior walls are considered wall space for required outlet spacing. Sliding patio or deck panels in exterior walls are exempt from this requirement [NEC 210.52(A)(2)]. See figure 1 for the receptacle layout in a typical room.
Figure 2. Typical receptacle outlet spacing requirements for kitchen countertops in dwelling unit kitchens
Space created by fixed room dividers, such as freestanding bar-type counter or railings, is considered wall space for the purpose of applying these receptacle outlet requirements at dwelling units. Railings create wall spaces where electrical appliances such as televisions, stereos or luminaires are commonly located. Floor receptacles are a common solution for railings and banister locations where receptacle outlets are required to be placed [NEC 210.52(A)(3)].
Where floor receptacles are installed to meet the receptacle outlet spacing provisions, they must be located within 450 mm (18 in.) of the wall they are intended to serve. Without receptacles located for these spaces, occupants often resort to the unsafe practice of using extension cords across walkways or doorways, or they place these extension cords under carpeting or other floor covering, creating a possible fire hazard [NEC 210.52(A)(3)].
Although not an enforceable requirement, a good rule of thumb for receptacle outlet spacing is to space receptacle outlets equal distances apart. Required wall receptacle outlets are in addition to any receptacle that is part of any luminaire or appliance that may be located within cabinets or cupboards, or located over 1.7 m (5½ ft) above the floor (NEC 210.52).
Electric baseboard heating units (fixed electric space heating) create a potential hazard. A flexible cord that is draped in front of or on the hot fins of the baseboard heater can create a fire and shock hazard. Listed baseboard heaters may contain instructions that prohibit the installation of the unit below receptacle outlets. There is no specific vertical distance or separation above which receptacle outlets are then permitted. The Code permits factory-installed receptacle outlets or outlets provided as a separate assembly by the manufacturer in permanently installed electric baseboard heaters to serve as the required outlet or outlets for the wall space utilized by such permanently installed heaters. These receptacle outlets are not permitted to be connected to the electric baseboard heater circuits. The branch circuit that serves that area must be used to supply the receptacle located in the baseboard heater (NEC 210.52).
Small Appliance Circuits (Kitchen)
The Code requires at least two or more 20-ampere small-appliance branch circuits to be installed at dwelling units to serve all receptacle outlets in the dwelling unit kitchen, pantry, breakfast room, dining room or similar area of a dwelling unit. The 20-ampere small appliance circuits are permitted to supply refrigeration equipment located in these areas as well [210.52(B)(1)].
The Code also permits an individual branch circuit for refrigeration equipment per NEC 210.52(B)(1) Ex. No. 2. Where installed, this refrigeration circuit must not be smaller than 15 amperes in rating. The receptacle supplying refrigeration equipment in the kitchen does not require GFCI protection if the receptacle outlet is located behind the appliance and is not readily accessible to serve the countertop.
Photo 1. Combinations AFCI overcurrent devices installed in dwelling unit panelboard
The two or more small-appliance branch circuits cannot have other outlets, with two exceptions. The term other outlets refers to lighting, appliance, and receptacle outlets that do not serve countertops or wall spaces in the kitchen, pantry, breakfast room, dining room, or similar areas. This means that additional circuits must be provided to supply lighting outlets in these areas, kitchen hood fans, built-in microwave ovens, dishwashers, garbage disposals, etc. A receptacle installed solely for an electrical clock in kitchens, dining rooms or related spaces can be supplied by one of the small-appliance branch circuits. Receptacles installed to provide power for supplemental equipment and lighting on gas-fired ranges, ovens or counter-mounted cooking units are also permitted to be supplied from one of the small-appliance branch circuits. Outdoor receptacles and other outlets not specified above are not permitted to be connected to the small appliance branch circuit(s) [NEC 210.52(B)(2)].
At least two of the 20-ampere small-appliance branch circuits are required to serve the countertop surfaces in the kitchen. Either or both of these two circuits can also supply other receptacle outlets in the same room or adjacent areas permitted on the small-appliance branch circuits such as a dining room or pantry receptacle outlets. No small-appliance branch circuit shall serve more than one kitchen. Some dwellings have a kitchen in the basement or in an in-law-type apartment in addition to the main dwelling kitchen. Each kitchen must be supplied by not less than two 20-ampere, small-appliance branch circuits [NEC 210.52(B)(3)].
Kitchen is defined in the Code as an area with a sink and permanent facilities for food preparation and cooking. Permanent facilities for food preparation and cooking are not defined; therefore, is a microwave oven “permanent facilities for food preparation and cooking?” The enforcing agency often has to use good judgment and discretion relative to making this determination to ensure that adequate circuitry and receptacle outlets are provided for the anticipated use.
Kitchen Receptacle Spacing
In kitchen and dining area countertop spaces of dwelling units, a receptacle outlet must be installed at each wall counter space that is 300 mm (12 in.) or wider. In addition, receptacle outlets must be installed so that no point along the wall line is more than 600 mm (24 in.) measured horizontally from a receptacle in that space. For applicable wall counter spaces, this means the first receptacle must be located not more than 600 mm (24 in.) from the edge of the counter space, and the next receptacle can be no more than 1.2 m (48 in.) from the first one, and so on along the wall counter space. Though not specifically mentioned here, the provision of measuring around the corner of the floor for wall receptacles is commonly accepted for wall counter spaces. This 600 mm (24 in.) rule is only applicable to wall or base countertops and does not apply to peninsular or island countertops [NEC 210.52(C)(1)].
Photo 2. Tamper-resistant receptacles (Courtesy of Pass & Seymour/Legrand)
The term appliance garage is referenced in NEC 210.52(C)(5). An appliance garage is often an integral part of the dwelling unit kitchen cabinetry. Although it is permitted to install a receptacle within the appliance garage, that receptacle is not permitted to serve as the required receptacle for the countertop space. Also any receptacle installed within an appliance garage located on the countertop must be GFCI-protected to meet the requirements of NEC 210.8(A)(6).
Receptacle outlets may be required to serve wall space behind sinks or ranges. Two figures are included in the Code to illustrate the condition (NEC figure 210.52). One illustration is for a sink or range that extends from the front face of the countertop. If the space between the sink or range and the wall is 300 mm (12 in.) or greater, a receptacle outlet is required to serve that space. The other illustration is of a sink or range mounted in a corner. If the space between the sink or range and the corner of wall is 450 mm (18 in.) or greater, a receptacle outlet is required to serve that space. The third function of both illustrations is to show where the measurement to the first required receptacle outlet starts at the sink or range.
Island Counter Spaces
At least one receptacle outlet is required to be installed at each island counter space with a long dimension of 600 mm (24 in.) or greater and a short dimension of 300 mm (12 in.) or greater. In essence, this means you can cut a pattern of those dimensions and any island counter space that is 600 mm (24 in.) by 300 mm (12 in.) or larger must have a receptacle outlet for that space. Only one receptacle outlet is required for the island countertop space regardless of how large it is unless a range or sink is installed in the island countertop that creates a 600 mm (24 in.) by 300 mm (12 in.) space on both sides of the range or sink. Additional receptacles, of course, can be added but are not required to meet the minimum provisions of the Code [NEC 210.52(C)(2)].
Peninsular Counter Space
Some kitchens include cabinet configurations that incorporate peninsular extensions from wall counter space. A peninsular countertop is measured from the connecting edge of the base cabinet. The Code requires a receptacle outlet be installed at each peninsular counter space with a long dimension of 600 mm (24 in.) or greater and a short dimension of 300 mm (12 in.) or greater. Like the island counter space, any peninsular counter space that is equal to or larger than 300 mm (12 in.) by 600 mm (24 in.) must have a receptacle outlet for that space. Again, only one receptacle outlet is required for the space regardless of how large it is unless a range or sink is installed in the peninsular countertop that creates a 600 mm (24 in.) by 300 mm (12 in.) space on both sides of the range or sink. Additional receptacles are permitted but are not required [NEC 210.52(A)(3)].
Separate Countertop Spaces
Dwelling unit kitchen countertop spaces separated by range tops, refrigerators or sinks are considered separate countertop spaces insofar as applying the rules for wall-counter, island and peninsula spaces. This means each side of one of these separators is considered an individual counter space, and measurement to determine if a receptacle is required must be made for each space. An example of this would be a rangetop installed at a dwelling unit kitchen island. If the countertop on the left side of the rangetop is 300 mm (12 in.) by 600 mm (24 in.) or greater and the countertop on the right side of the rangetop is also 300 mm (12 in.) by 600 mm (24 in.) or greater, a receptacle outlet would be required on each side to serve the two separate island countertops on each side of the island-mounted range [NEC 210.52(C)(4)].
Counter Receptacle Outlet Location
Receptacle outlets are generally required to be located above but not more than 500 mm (20 in.) above dwelling unit countertops in order to serve that countertop [NEC 210.52(C)(5)]. In addition, receptacles are not permitted to be installed in a face-up position on dwelling unit work surfaces or countertops [NEC 406.4(E)]. A receptacle outlet that is not readily accessible by an appliance garage or an appliance that is fastened in place or otherwise restricts ready access to the receptacle cannot be considered as one of the required receptacles.
Receptacle outlets are not permitted to be installed more than 300 mm (12 in.) below the kitchen countertops in order to serve that countertop. Receptacle outlets are not permitted to be installed below a countertop unless one of two exceptions applies. The first is for the construction for the physically impaired. The second applies to an island or peninsular counter space where the countertop is flat across the entire surface (no backsplash) and there are no means to mount a receptacle within 500 mm (20 in.) above the countertop. If the island or peninsular counter space has more than one level separated by a backsplash or other vertical surface, then the required receptacle cannot be mounted below the countertop. Cabinets mounted above such an island or peninsular countertop can be used to meet this requirement if the bottom of the cabinets is within 500 mm (20 in.) of the countertop.
Receptacle outlets mounted below the countertop for either of these exceptions shall not be located where the countertop extends more than 150 mm (6 in.) beyond its support base. This addresses the safety issue of kitchen appliances with fairly short cords and the cord wrapping around the countertop and becoming more vulnerable to snagging and pulling appliances with hot liquids off the countertop [NEC 210.52(A)(5) Exception].
Arc-Fault Circuit-Interrupter Protection
There may not be an area in the Code that is more specific to dwelling units than arc-fault circuit interrupter (AFCI) requirements. Currently, AFCIs are only required in dwelling units. An arc-fault circuit interrupter (AFCI) is a device intended to provide protection from the effects of arcing type faults. The device recognizes the characteristics that are unique to arcing, and will cause the affected circuit to be quickly de-energized when it detects a sustained arcing type fault.
The AFCI does not protect people from electric shock in the manner of ground-fault protection for personnel. It also is not intended to take the place of the overcurrent protective device located at the source of the circuit. An AFCI device will potentially reduce the number of residential fires by mitigation of arcing effects in damaged electrical wiring. The damaged conductors may be part of the permanent wiring of the building or any electrical cords and equipment connected to the protected circuit.
The Code requires that “All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms or areas to be protected by a listed, combination type, arc-fault circuit interrupter(s).” Combination AFCI devices provide protection from both parallel (two opposite polarities) and series (break in a conductor) arcing events. Manufacturers have integrated the technology into inverse-time circuit breakers as well as other type devices. The listing standard permits the technology to be built into other types of electrical devices such as receptacles. At the time of this writing, there are no listed receptacle-type AFCI devices available. Perhaps you will see these receptacle-type AFCI devices in the very near future to meet the exceptions to AFCI requirements in dwelling units. The Code requires the entire branch circuit to be AFCI-protected with two exceptions. Exception No. 1 permits an arc-fault device to be installed at the first outlet of the branch-circuit. The circuit conductors between the branch-circuit overcurrent device and the arc-fault circuit device at the first outlet have to be installed in RMC, IMC, EMT or steel armored cable, Type AC, meeting the requirements of 250.118 using a metal outlet and/or junction boxes.1 Exception No. 2 permits the omission of AFCI protection for an individual branch circuit to a permanently installed burglar/fire alarm system installed in accordance with NEC 760.41(B) and 760.121(B) where the individual branch circuit is installed in RMC, IMC, EMT, or steel armored cable, Type AC, meeting the requirements of 250.118, with metal outlet and junction boxes. This exception does not apply to single- or multiple-station smoke alarms, which require AFCI protection as an outlet located in the areas mentioned in 210.12 of a dwelling. Single- and multiple-station smoke alarms are supplied by a branch circuit covered by the requirements of Article 210, not through a non–power-limited fire alarm circuit powered by a fire alarm control panel (NEC 210.12).
Tamper-Resistant Receptacles in Dwelling Units
The Code now requires all 125-volt, 15- and 20-ampere receptacles installed in dwelling unit areas specified in NEC 210.52 to be of the listed tamper-resistant type. This brings an added measure of safety to toddlers in the home environment. What areas are specified in 210.52? Kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, sunrooms, bedrooms, recreation rooms, or similar rooms or areas, bathrooms, outdoors, laundry rooms, basements, garages, and hallways. Areas that are not specified in 210.52 would include areas such as attics, crawl spaces, closets (if you do not consider the closet part of the bedroom).
In this article, we have just scratched the surface of the specific NEC requirements for dwelling units. There are many, many more dwelling unit requirements as indicated in the companion list to the article. A very good reference source to get expanded, in-depth information on these dwelling unit specific requirements is IAEI’s One- and Two-Family Dwelling Electrical Systems textbook.
Residential wiring is undoubtedly the most common and abundant type of electrical installation in the world. Residential occupancies are where people live, families are raised, and where people sleep. Safe electrical installations are just as important in residential occupancies as they are in any other type of occupancy. Safe electrical installations require several key components. Anyone who designs, installs, or inspects electrical systems in dwelling units must be thoroughly familiar with these requirements for safe installations, as found in electrical codes and product safety standards. These codes and standards must be followed carefully to provide an installation that is essentially free from electrical hazards. It is important that qualified persons perform these dwelling unit installations and inspections.
Tags: AFCI, arc fault, electrical code, GFCI, home wiring, house wiring, residential, residential electric codes, residential wiring, Vermont code update —
As we all know, in the past few years, technologies have grown at a staggering pace. New products come out everyday, and the latest and greatest thing is always just around the corner. Lighting is no different. Several years ago, LED(Light Emitting Diodes) began to emerge as a viable lighting solution. Since that time, LED’s have grown to become a major part of the lighting industry. The benefits of LED’s are numerous and significant. The most important benefits are the following:
1. LED’s are incredibly energy efficient. For the same lumen output, they are significantly lower wattage than any other type of light fixture, cutting energy costs by a significant amount.
2. The lights themselves last for a very long time, reducing maintenance costs. LED’s are usually rated for around 50,000 hours of use. To put it in a perspective, a metal halide fixture, a commonly used outdoor fixture, has a life of usually around 20,000 hours. This means that the LED will outlast the metal halide by roughly double.
3. There are good rebates in Vermont right now for installing LED fixtures. Efficiency Vermont at this time offers rebates right now that usually covers around half of the cost of many fixtures.
LED’s, though still somewhat expensive, have many benefits and create a good light which will match many existing fixtures. The rebates offered by efficiency Vermont will also not be around forever, so now is the time to install these fixtures. At Rob Stubbins Electric we keep ourselves current with new products and emerging technologies. We have installed many new LED fixtures, and continually try to make sure we are giving our customers the best quality, most energy efficient lighting. If you would like more information on LED’s or other energy efficient lighting, or are interested in upgrading to LED’s, give us a call and we can answer questions you may have, tell you what rebates are available, and let you know how you can cut down on your energy costs.
Tags: energy, Energy Efficiency, Energy Efficient, Energy Efficient lighting, LED, LED cost, LED rebates, LED's, Light Emitting Diode —
This article comes from an NFPA(National Fire Protection Association) news update. This discusses GFCI (Ground Fault Circuit Interrupter) protection, it’s history, and how it has evolved in the National Electric Code. GFCI receptacles interrupt power to a circuit when it senses an imbalance of current between the neutral and ground. Its purpose is to protect against hazardous shock, especially from water coming in contact with electricity. This device is now required in essentially any place where water could come into contact with Electricity and cause a shock.
The Ground-Fault Circuit-Interrupter Protection Journey
Ground-fault circuit-interrupter (GFCI) protection has been in the National Electrical Code® (NEC®) for 50 years. Many thought there could not possibly be any additional locations where GFCI protection was needed, but the 2011 edition shows that there are still areas that can benefit from this protection. Actually, new GFCI requirements have been added in every edition since 1971, but most people are only aware of those specified in 210.8. This article looks back at the history of GFCI requirements. Although Articles 210, 590 and 680 — those that have the longest history — are the focus, other notable requirements are included. Also, Code terminology has changed over the years; the terms used will be from the edition referenced.
The Protection Technique Arrives.
The first mention of ground-fault protection occurred in the 1962 NEC with the introduction of Article 680 for swimming pools. It is generally accepted that electricity and water are not a good combination, and there was a concern for the shock hazard associated with underwater lighting. An approved fail-safe ground detector device could automatically de-energize the circuit for underwater lighting operating at greater than 30 volts. This fail-safe ground (not yet called GFCI) detector was not the only allowable method; an approved grid structure or similar safeguard was an alternative.
A 1965 modification to the Code required all underwater lighting fixtures to perform reliably under any likely combination of fault conditions to prevent a shock hazard. Four methods could accomplish this requirement, including the use of “differential type circuit protection”, the precursor to the term “ground-fault circuit interrupter.”
What Is GFCI?
The definition of Ground-Fault Circuit Interrupter appeared in Article 680 (in the 1968 edition) as “a device whose function is to interrupt the electric circuit to the load when a fault current to ground exceeds some predetermined value that is less than that required to operate the overcurrent protective device of the supply circuit.” GFCI was still only one of the protection methods permitted for underwater fixtures. An interesting requirement was that conductors on the load side of the GFCI device were to be kept entirely independent of all other wiring and electrical equipment.
It was not until 1971 that GFCI protection became a “required” protection method. Even though underwater lighting fixtures were the first allowed this protection they were not the first required to have it. A failed grounding connection presents an electrical hazard, particularly with the number of handheld power tools and extension cords used around a construction site. So the first GFCI requirement (first simply because it occurred in Section 210-7) was for all single phase, 15- and 20-ampere receptacles used at a construction site. A few sections further, GFCI protection was required for all outdoor 120-volt, 15- and 20-ampere receptacles in residential occupancies, essentially for the same reason as for construction sites. This section also specifically permitted GFCI protection for “other circuits, occupancies and locations” if added protection was desired. In Article 680, protection included all electrical equipment used with storable pools and all receptacles within 15 feet of an indoor pool . The expansion of GFCI protection had begun.
Section 210-8 Arrives
The section titled “Ground-Fault Circuit Protection” debuted in 1975 for residential occupancies and construction sites. That year, because of the potential shock hazard, residential bathroom receptacles joined the list of locations requiring GFCI protection. At construction sites, the provision now applied only to 120-volt receptacles not part of the permanent wiring; but with prevalence of generators, an exception was granted for receptacles on portable generators of 5 kW or less. The GFCI requirements around pools continued to expand to lighting fixtures and outlets within 16 feet of the pool. Many pools were being added to dwellings in the 70s, so a retroactive provision covered existing fixtures and outlets within 5 feet of a newly installed pool. Finally after 12 years of using various protection methods, GFCI protection became the only method permitted for re-lamping underwater lighting fixtures. In 1975, mobile homes and recreational vehicles (Articles 550 and 551) began to parallel the GFCI requirements for residential occupancies, and GFCI protection came to health care facilities (Article 517).
Ground-fault circuit-interrupter protection requirements took time to expand. Concerns about the new technology, false tripping, financial burden, and the lack of data were cited as reasons. Still, 210-8(a) of the 1978 NEC added GFCI requirements to garages of dwelling units, partially due to concern with the amount of grounded (concrete) surface, and the fact that many hand-held tools did not have an equipment grounding conductor (for the younger crowd who have only used double-insulated ABS tools, metal used to be the hand-held power tool housing material of choice). Data regarding a grounding system that was verified as being intact supported the addition of an exception to the 210-8(b) construction site requirements. This exception introduced the assured grounding program as an alternative to GFCI protection. GFCI protection also became a requirement for marina receptacles (Article 555).
Exceptions for garage receptacles that were not accessible — or were used for appliances in a dedicated space — first appeared in 1981. Thirty years ago, many appliances had high leakage currents, and ones with motors often were capable of tripping a GFCI device; therefore, fixed appliance locations were exempted. Non-accessible receptacles — such as on the ceiling for a garage door opener — were likewise exempted, with the expectation that the receptacle would not be used with extension cords or hand-powered tools.
In the 1984 edition, 210-8(b) was changed to address hotel and motel bathrooms, because those bathrooms present the same hazards as dwelling bathrooms. Construction projects are temporary conditions, so the GFCI requirements for these areas previously in 210-8(b) were relocated to Article 305, Temporary Wiring.
The GFCI requirements expanded in 1987 to additional dwelling unit receptacles. The Code required the installation of at least one receptacle in a basement. With the concrete and portable tool use in this area, GFCI protection became a requirement for that one receptacle. The intent of the wording “above the countertop and within 6 feet of a kitchen sink” was clarified to exempt appliances (disposal, refrigerator, etc.) from the GFCI requirement. Additionally, dwelling boathouses (due to the nature of the location and the use of portable tools) became another protected location. The receptacles in commercial garages (Article 511) were included for the same reasons as those in a dwelling unit garage.
All receptacles in crawl spaces and “unfinished” basements appeared as 210-8(a)(4) in the 1990 edition, with exemptions for a single appliance, a laundry circuit, and a permanently installed sump pump. The substantiation for these exceptions was similar to that for the garage exemptions discussed above.
More Locations Get Protection
Section 210-8(a)(5) was modified in 1993 to apply to receptacles that serve — as opposed to being above — the kitchen countertop, and to add wet bar sinks. This edition introduced Section210-8(b), “Other than Dwelling Units” when the title was changed from ”Hotels and Motels.” This title change added the GFCI requirement to the bathroom of every occupancy. The Code required HVAC service receptacle could be located on a roof, thus rooftop receptacles became 210-8(b)(2). To provide protection not initially installed, receptacles being replaced (210-7) were to be replaced with a GFCI receptacle, if GFCI protection was required by the current Code. The hazards at a construction site are the same whether the supply circuits are temporarily or permanently wired, so any receptacle used there required GFCI protection (Article 305).
In the 1996 NEC, dwelling unit grade-level unfinished accessory buildings, and every kitchen counter-top receptacle (not just those within 6 feet of the sink), were added to the list of locations requiring GFCI protection. Also added was the exception for snow-melting equipment receptacles that were not readily accessible. New Article 552 for park trailers tracked the GFCI requirements for mobile homes.
Many pool pumps at private clubs and apartment complexes are hard-wired, and these pools are often maintained by personnel not familiar with bonding and grounding requirements. The concern for protection of the public using these facilities warranted adding the GFCI requirement in the 1999 Code to 125- or 240-volt, 15- and 20-ampere pool pump motors, whether they were direct connected or cord-connected. This edition also brought another change to temporary installations (which were at that time in Article 305) when it expanded GFCI requirements to cover 125-volt, 30-ampere receptacles as well as any other receptacle used temporarily.
Kitchen receptacles in all non-dwelling units were added to 210.8(B) in 2002. The 5 kW or less generator receptacle exemption was dropped in this edition, thereby placing the GFCI requirement on all generators used at construction sites (moved to Article 527 at this point). Article 680 now addressed both dwelling and other than dwelling unit pump motors, but the requirement only applied to receptacles rated 120 through 240 volts, 15 or 20 amperes. Two new articles (647 and 682) added GFCI protection for receptacles for sensitive electronic equipment and for receptacles within the datum plane of bodies of water.
Sinks, Kitchens and Other Locations
Utility and laundry sinks very often do not have a countertop associated with them. Therefore, a 2005 revision removed the countertop criteria for wet bar, laundry, and utility sinks, thereby requiring GFCI protection for any receptacle within 6 feet of these dwelling unit sinks. “Commercial and institutional” were added as qualifiers for application of the GFCI requirements in other than dwelling unit kitchens. These kitchens were distinguished from others by adding what was to become the definition of a kitchen (“an area with a sink and permanent facilities for food preparation and cooking”). In 210.8(B), outdoor receptacles accessible to the public were required to have protection. Article 680 added all 125-volt receptacles within 20 feet of storable pools to the growing list of spaces requiring protection. This edition clarified that GFCI protection at temporary installations (finally Article 590) included both service and on-site generator supplied receptacles. Carnivals and fairs (Article 525) listed locations where GFCI is required, is not required, and is not permitted. Vending machines (Article 422) without integral GFCI had to be connected to a GFCI protected outlet.
Rules Tighten and Exceptions Disappear.
Initially a freezer may be plugged into a garage receptacle, but there is no assurance that a new owner will do the same; it is common to see extension cords plugged into the ceiling receptacle intended for a door opener. The new owner using these receptacles for power tools does not have the required protection. Neither of these conditions were anticipated when the exceptions appeared in 1981. The 2008 edition saw the 210.8(A) exceptions (except those for fire or burglar alarm systems) removed for garages and unfinished basements. This edition also tightened non-dwelling unit requirements to cover all kitchens and outdoor locations. It also covered all receptacles within 6 feet of any sink in non-dwelling units, with exceptions for industrial laboratories and patient care areas. The GFCI requirement for pool pumps reverted back to its earlier form — to cover cord-and-plug units as well as those with a direct connection. Ground-fault circuit-interrupter protection was included for all receptacles under new Article 626, Electrified Truck Parking Spaces.
Where Are We Today?
This brings us to 2011 where, rather than periodically adding locations where a sink might be present, receptacles within 6 feet of any sink (other than in a kitchen) require GFCI protection. There are three non-dwelling areas that were missing GFCI protection prior to the 2011 NEC: indoor wet locations such as inside a car wash , locker rooms with shower facilities. (wet persons using an electric hair dryer or shaver in this area needed protection), and garages [which may become wet with snow, rain, even spilled fluids, and in which portable tools and lighting or diagnostic equipment are used]. The garages covered by this new requirement are not the commercial garages covered under Article 511. For temporary installations (Article 590), the GFCI requirement is also placed upon all 125-volt and 125/250-volt, 15-, 20-, and 30-ampere receptacles of a generator 15 kW or less.
After 50 years, it is impossible to know how many lives have been saved or injuries avoided since the introduction of GFCI requirements in the NEC. One thing for certain is that GFCI devices have helped accomplish the purpose of the NEC; the practical safeguarding of persons from hazards arising from the use of electricity.
Christopher D. Coache is Senior Electrical Engineer at NFPA where he is primarily involved with electrical codes and standards. He serves as staff liaison for NFPA 73, NFPA 110 and NFPA 111. He has been involved in electrical safety for 25 years and has participated in the development of national and international standards.
Tags: electric shock, GFCI, GFCI protection, GFI, Ground Fault, Ground Fault Circuit Interrupter, NEC, NFPA —
The following is an article which appeared in the January- February edition of the International Association of Electrical Inspectors magazine. It certainly contains some good information from a respected and knowledgeable source regarding something that is occurring in our area.
The article can be found at http://www.iaei.org/magazine/2012/01/smart-meter-numbers-benefits-expanding/
The term smart meter is becoming much more common around the country. These new digital meters for recording electricity use are replacing the traditional analog meters that homes and businesses have used since the early 20th century.
A new survey by the Institute for Electric Efficiency (IEE) shows that as of September 2011, electric utilities have installed 27 million of the new smart meters. This equals more than 22 percent of all U.S. households. By 2015, it is projected that approximately 65 million smart meters will be installed, representing 54 percent of all homes in the country.
Like their predecessors, smart meters are a technology for measuring how much electricity an electric utility customer has used over a given amount of time. But instead of waiting to be manually read once a month, as most meters are today, a smart meter can automatically record electricity use every hour or even on demand.
Smart meters also include the capability for creating a two-way communication link between a utility and its customers. For consumers, this information exchange opens the door for better understanding and control of their home’s electricity use.
Given that a smart meter can record electricity use every hour or in some cases every 15 minutes, consumers can now monitor how much they are using before their electric bill comes at the end of the month. In some cases, electric utilities are making available a Web portal or other devices that consumers can use to get daily updates about their electricity use. Studies have shown that just by making consumers aware of their electricity use encourages them to save energy by making small changes such as adjusting the thermostat, switching to compact fluorescent light bulbs, or unplugging appliances when not in use. Consumer savings, derived from knowing how much electricity they are using, are typically about five percent of their monthly bill.
In the not too distant future, the two-way communication capabilities of smart meters also will enable consumer-friendly efficiency concepts like “Prices to Devices.” In this scenario, a utility sends price signals in near real-time to “smart” home controllers, smart thermostats, or new smart appliances like air conditioners, washers/dryers and dishwashers. The devices, in turn, process the information based on what a consumer’s preferences are and operate accordingly. If a consumer feels a given price is too high, a particular appliance can be programmed not to run during that period.
This way, the house or office responds to the occupants, rather than vice-versa. Because this interaction occurs largely in the background, with minimal human intervention, there’s a dramatic savings on energy that would otherwise be consumed. This type of program has been tried in the past, but without smart meters and other communication and electronic technologies, it did not possess any of the potential that it does today.
Smart meters combined with the other advanced digital upgrades that electric utilities are making to their electric transmission and distribution grids will give them real-time awareness about how their electric systems are operating. This in turn creates a number of benefits for utilities and their customers alike:
More Constant Voltage Levels — The capability to maintain more constant voltage levels throughout the electric system benefits all customers, especially those with digital equipment at home or at work. And more constant voltages also results in lower electricity losses due to resistance, which is a direct saving for customers.
Substation Monitoring and Diagnosis — These distribution automation applications are not seen by customers, but they contribute to greater system reliability.
Distribution Power Systems Management — Greater ability to integrate and control distributed energy resources, such as rooftop solar units and even devices that can store electricity, such as batteries.
Electric Vehicles — Ability to send price signals so that customers can decide when to charge their vehicles, helping them to avoid charging their electric cars during high-cost periods.
Demand Response Tools — These technologies give customers more control over their monthly bills by helping them to respond to electricity price signals and avoid electricity use during high cost peak-demand periods.
Outage Management Systems — Outage management systems benefit customers through faster outage detection and restoration, and can be extremely important to customers in remote or hard-to-serve locations.
Combined, all of these new capabilities allow electric utilities to more closely monitor and control all of the points on their system between the power plant and the customer.
Smart meters return a number of other benefits to electric utilities as well. Through their energy management capabilities, smart meters enable utilities to reduce the demand periods. This puts downward pressure on electricity prices, and it helps to offset the need for new power plants and more transmission and distribution lines, which in turn helps to keep electricity prices lower. These savings also translate into potentially lower carbon and other air emissions from power plants. In returning all of these benefits, society at large benefits as well.
IEE recently conducted a study on how the benefits of smart meters compare with their costs. The paper, “The Costs and Benefits of Smart Meters for Residential Customers,” found that across a range of electric utility and customer types, the benefits for a utility to invest in smart meters and related equipment will exceed the costs. And the savings produced by the investment in smart meters will help to keep the price of electricity down for everyone.
In our study, we took a very conservative approach and assumed fairly low participation rates by customers in different utility energy management program offerings even after 20 years. If customers can choose their preferred rate plans, programs, and enabling technologies, and if significant investment is made in consumer engagement, the benefits to customers, utilities, and society would be even greater.
Interestingly, our analysis also revealed that the strategy with the potential to return the greatest financial benefit to utilities and customers alike is to focus on accelerating the adoption of electric vehicles (EVs). Households that have EVs, which represented only about 1.25 to 1.5 percent (12,500 to 15,000) of the hypothetical 1 million customers we accounted for in a service territory, created a disproportionately high share of the overall consumer-driven savings, indicating that even modest increases in EV adoption will have a large impact on benefits.
Note that the paper did not include distributed generation resources such as solar panels or residential fuel cells. Including them could push the benefits even higher.
Although smart meters are relatively new to the utility industry, they are treated with the same due diligence and scrutiny associated with electronic meters and older electromechanical counterparts. These meters meet or exceed national standards such as American National Standards Institute (ANSI) C12.1 for meter accuracy and design. In addition, equipment used to certify meter performance must be traceable to the National Institute of Standards and Technologies (NIST), a federal agency that works with industry to properly apply technology and measurements. Other standards in use for the Smart Meter installations include National Electric Code (NEC) for home electrical wiring, National Electrical Manufacturers Association (NEMA) and Underwriters Laboratories (UL) for enclosures and devices, and National Electric Safety Code (NESC) for utility wiring.
Today, electric utilities are installing smart meters and building new infrastructure that will enable them to continue to meet their customers’ needs in this decade and beyond. They will also enable the customer to get even more benefits from using electricity in the future.
Tags: cvps, IAEI, meters, smart energy, smartgrid, smartmeters, smartpower, Vermont smart meters —
This article appeared in the March/April 2010 edition of the IAEI(International Association of Electrical Inspectors) magazine. It is not commonly known that electrical equipment must be listed for whatever purpose it is used for, and for whatever equipment it is being used with. In the example put forth in this article, we see that if a circuit breaker is replaced it must be with breaker that has a UL listing for the panel it is being put in. In most cases (but not all as the author points out) that means it must be made by the same manufacturer. This article shows why not just any circuit breaker can be installed in any panel.
I have an old panelboard made by a company that was sold and no longer produces panelboards or circuit breakers under their old name. How do I find circuit breakers listed for use in the panel when the manufacturer is no longer in business, can I use any circuit breaker that fits?
Over the years the electrical industry has undergone a lot of consolidation. Where there once were many companies that made panelboards and circuit breakers, there are now only a few. That leaves a big hole in sourcing replacement breakers for these panelboards that may now seem obsolete. The circuit breaker compatibility marking on some of these older listed panelboards may specify types of circuit breakers that are no longer in production and difficult to find. If the original equipment manufacturer (OEM) circuit breakers specified on the panelboard cannot be found, it is not acceptable to just install any circuit breaker that fits.
A panelboard to which a unit, such as a circuit breaker, switch, or the like, may be added in the field is required to be marked to identify the units that can be added. Units made by different manufacturers or of a different style are not identical in all details and therefore may not be interchangeable.
Plug-in clips and blades must be matched if poor connections and overheating are to be avoided. Additionally, over-surface and through-air electrical spacings, between live parts of opposite polarity and to grounded metal, often depend on the proper mating of units and the bases into which they are plugged or bolted.
The only exception is for UL classified molded-case circuit breakers rated 15 to 60 A, 120/240 V ac, that have been investigated and found suitable for use in place of other listed circuit breakers in specific listed panelboards.
The circuit breakers are classified under the product category Circuit Breakers, Molded-Case, Classified for Use in Specified Equipment, (DIXF) located on page 95 in the 2009 UL White Book and are limited for use with panelboards rated 225 A or less, 120/240 V ac. These circuit breakers are classified for use in specific panelboards in accordance with the details described on the circuit breaker, or in the publication provided therewith. These breakers are suitable for use in equipment connected to circuits having a maximum available system short-circuit current of 10 kA.
Classified breakers are required to comply with the same Standard for Safety for Molded Case Circuit Breakers, UL 489 as listed molded case circuit breakers; however, they are typically manufactured by a different OEM than that of the manufacturer of the panelboard.
Tags: breakers, circuit breakers, electrical safety, IAEI, UL, UL listing —