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My second McGraw-Hill book for electricians, Troubleshooting and Repairing Commercial Electrical Equipment, now available from Amazon --






Now I've written a third McGraw-Hill book, out soon. The title is The Electricians's Trade Demystified. It is available for pre-order from Amazon. Click below --



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Milwaukee 49-22-4085 17 Piece Deluxe Electricians' Hole Saw Kit

Milwaukee 49-22-4085 17 Piece Deluxe Electricians' Hole Saw Kit

Milwaukee 49-22-4085 17 Piece Deluxe Electricians' Hole Saw Kit Since its founding in 1924, Milwaukee has focused on a single vision: to produce the best heavy-duty electric power tools and accessories available to professional user. Today, the Milwaukee name stands for the highest quality, durable and reliable professional tools money can buy. This deluxe 17 piece Electricians' Hole Saw Kit has the ultimate range of diameters available. The 12 diameters include: 5/8 inch, 3/4 inch, 7/8 inch, 1 inch, 1-1/8 inch, 1-1/4 inch, 1-3/8 inch, 1-1/2 inch, 1-3/4 inch, 2 inch, 2-1/2 inch, and 3 inch. The kit also includes arbor 49-56-7000 for hole saws up to 1-3/16 inch and arbor 49-56-7140 for hole saws 1-1/4 inch and larger. Additionally the kit has three pilot bits 49-56-8000 and an impact resistant plastic carrying case. The case is also sold separately as 48-55-0784. The hole saws in this kit are of the 6 teeth per inch design. Milwaukee 49-22-4085 17 Piece Deluxe Electricians' Hole Saw Kit Features: • Deluxe assortment of 12 hole saws, two arbors, and three pilot bits • Hole Saws: 5/8 in., 3/4 in., 7/8 in., 1 in., 1-1/8 in., 1-1/4 in., 1-3/8 in., 1-1/2 in., 1-3/4 in., 2 in., 2-1/2 in., 3 in.




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Here is a selection of the most significant electricians' books available online today, at the best prices around. Clicking on any logo provides access to reviews and ratings by electricians. A good place to start is with the 2008 NEC Handbook, which contains the complete text of the current code plus extensive commentary, diagrams and illustrations. Other books of interest for the electrician are available as well.

This article originally appeared in Cabling Business Magazine --

NEC Mandates for Low-Voltage Cabling in Metal Raceway


By David Herres


We examine the latest edition of the National Electrical Code and see how these regulations govern metal raceway for structured cabling--

The National Electrical Code (NEC) appeared in 1897 and since 1911 has been revised and published by the National Fire Protection Association (NFPA). NEC 2008 is the 51st edition. A new revision currently comes out every three years, always with significant changes. The general trend is for more stringent mandates, although in some cases requirements are dropped or partially relaxed. The stated purpose of the Code is "the practical safeguarding of persons and property from hazards arising from the use of electricity."

As ratified by NFPA, the Code has no legal standing on its own, but is offered up to countries, states and municipalities to amend and enact into law as they see fit. The Code is applicable to all low-voltage cabling (with a few exceptions, such as most utility-controlled installations and underground in mines).

NEC chapters 1-4 apply generally and it is here we find the basic design specifications and installation protocols for non-utility electrical work, residential, commercial and industrial. Chapters 5-8 amend those earlier chapters and contain rules for special occupancies (Chapter 5), special equipment (Chapter 6), special conditions (Chapter 7) and communications systems (Chapter 8). Within these latter chapters are the somewhat more lenient rules for low-voltage cabling. Despite the relaxed mandates, some aspects of low-voltage cabling are actually more stringent, so care must be taken to research a job meticulously if you are venturing into a new area.

In regard to conduit, most low-voltage work does not require it, but there are a few applications where it is mandated while in certain other instances it is highly appropriate. The ubiquitous electrical metallic tubing (EMT) is technically not conduit, but it is commonplace to talk about doing a job "in conduit" when using this excellent raceway.Characterized by its thin wall, this pipe is usually galvanized steel. It is not to be threaded in the field. Couplings and other fittings are held in place by set screws. For wet areas, compression fittings are used.

NEC Article 725 addresses remote control and signaling circuits, which are: Class 1 power-limited, Class 1 non-power-limited, Class 2 and Class 3. Class 1 circuits are comprised by default of those remote control and signaling circuits which do not fall within the low voltage and power limits of Class 2 and Class 3. They can actually go up to 600 volts and the rated output in volt-amps is not limited.

There is also another category of remote control and signaling circuits that is considered Class 1. It is made up of remote control circuits for equipment whose failure to operate introduces a direct fire or life hazard. These two seemingly unrelated types of circuits go into the Class 1 category by virtue of the fact that both merit special treatment in terms of protection and separation from Class 2 and Class 3 low-voltage circuits, as well as other types of low voltage cabling.

Remote control circuits for safety equipment must be wired using metallic sheathed (C) cable or better. The Code lists acceptable wiring methods starting with the most extreme: rigid metal conduit (RMC), intermediate metal conduit (IMC), rigid non-metallic conduit (RNC), EMT, mineral insulated cable (MI), MC, or cable suitably protected from physical damage.

RMC looks from the outside like galvanized steel waterpipe, the threads are interchangeable, but it is listed for electrical installations. It is suitable for the most extreme environments. (Note: Water pipe should never be used where raceway is called for. Since it is not listed, such usage would not be NEC compliant. One problem is that the inside of water pipe is rougher, so damage would occur when pulling conductors.) RMC is very expensive and time consuming to install. Other than full-length pieces have to be cut, threaded and reamed in the field and larger sizes require use of a power bender. RMC is appropriate only where required, such as in some hazardous (classified) areas.

IMC is similar, but a little lighter and slightly less expensive. It is permitted in all environments but, like RMC, is not recommended for most work.

RNC, the familiar PVC conduit, is acceptable for all but the harshest environments. It is relatively inexpensive and easy to work, but has some drawbacks. One problem is that it has a greater expansion coefficient than steel, so slip joints have to be used in long runs that may be exposed to temperature variation. When ambient temperature rises, unsightly sagging can occur, particularly in long horizontal runs on the outside of a building. RNC is good for corrosive and wash down environments such as dairy barns, and it is excellent for underground work. In any event, PVC water pipe is not to be used; only the gray ultraviolet resistant listed pipe is permitted for electrical work.

EMT is the pipe of choice for most Class 1 and other cabling where raceway is required. It is easy to cut and bend using simple tools, and it is much less expensive than RMC. When supported at proper intervals (NEC Article 358), sagging and thermal expansion are not a problem. It is recommended that low-voltage technicians and electricians become adept at this type of work.

MI offers excellent protection and is allowed in harsh environments, but it is rarely used because the installation, particularly terminations, are labor intensive. Type MI is made up of conductors surrounded by a highly compressed refractory mineral insulation enclosed within a liquid tight and gas tight continuous copper or alloy steel sheath. As soon as it is cut, a termination fitting must be installed to prevent entrance of moisture.

MC looks at first glance like the old BX that was used in residential construction years ago. It is made up of conductors inside a corrugated or solid flexible sheath, usually aluminum. It is available in 250-foot rolls and is easy to work with The sheath is cut with a hand-cranked MC cutter and where permitted it can be spliced into EMT using a four-by-four box in order to fish through concealed spaces or navigate around obstacles where it is not practical to bend EMT. Since MC is permitted (in Article 330.104) to have copper conductors as small as 18 AWG, it lends itself to some lo-voltage cabling.

In addition to Class 1 remote control and signaling applications involving safety-control equipment, there are a number of instances where raceway is necessary. For example, Class 2 and Class 3 wiring must not occupy the same enclosure with conductors of electric light, power, Class 1, non-power-limited fire alarm circuits, and medium power broadband communication circuits. However, in enclosures, Class 2 and Class 3 circuits can be put in a raceway to separate the from Class 1, non-power-limited fire alarm and medium power network-powered broadband communication circuits. Notice that this permitted instance does not allow Class 2 and Class 3 wiring to coexist within an enclosure with power and light circuits even if one or both are in raceway.

Similarly, Chapter 8, which deals with communications systems, says that these wire and cables have t be at least two inches from conductors of electric light, power, Class 1, non-power-limited fire alarm or medium power network-powered communications circuits. However, an exception permits these diverse voltage and power levels to be closer than two inches if one of the categories is in raceway.

As you can see, there is a definite parallelism in NEC treatment of remote control and signaling circuits and other types of low-voltage cabling. And yet significant differences abound. The best policy is to consult the national Electrical Code, as well as other regulatory specifications and any local ordinances before doing work in a new area.

If an electrical inspector picks up on a misapplication,m it could mean costly rework and project delay. Far worse, a design or installation flaw could lay dormant for a period of time and eventually become a threat to human life. NEC includes a number of instances where raceway protection is required. Articles 720, 725, 760, 770 and Chapter 8 all cross-reference other applicable NEC articles.

Noteworthy in regard to this discussion of low-voltage cabling and raceways are Articles 500 through 516 and 517 if you are doing an installation in a hazardous (classified) area.

Class I, Division 1 areas are the most hazardous. A Class I location (not to be confused with Class 1 wiring) is defined a that in which flammable gases or combustible liquid produced vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures. Class II is a location hazardous because of the presence of combustible dust. While less dangerous than Class I, Class II still has the potential for enormous explosions since the finely divided particles present a large surface area in contact with atmospheric oxygen. Metallic dusts, such as aluminum and magnesium, are particularly critical since the particles are also conductive.

Class III locations are characterized by the presence of easily ignitable fibers or where materials producing combustible flyings are handled, manufactured or used but in which these fibers and/or flyings are not likely to be in suspension in the air in quantities sufficient to create ignitable mixtures. Class III is less hazardous that Class II or I, but nevertheless merits special treatment since it presents more of a threat to property and life than wiring in unclassified areas.

Within each of these three classes are two divisions. Division 1, in each case, presents more of an immediate danger than Division 2, usually because of the way the materials are handled or the distance from those materials.

So there are six distinct areas which need to be delineated with boundaries, and in each of these areas, different cabling methods and materials are called for. Typically, the higher in the hierarchy (with Class I Division 1 at the summit), the more expensive are the materials and the more labor involved in installing them.

Cabling designers and installers must be aware of any hazardous (classified) areas within a jobsite and respond accordingly. The best strategy is to locate cable and equipment outside any classified area or within, for example, a Division 2 area. If necessary to install non-power-limited cabling within a classified area, metal raceway is usually mandated. In Class I, Division 1, RMC or IMC is compliant.

Other than hazardous areas, raceway is required for certain other situations and this is spelled out in the articles involved. An example is Article 620, which deals with elevators, dumbwaiters and escalators, moving walks, platform lifts and stairway lifts. Article 620.21, titled Wiring Methods, requires conductors and optical fibers to be MC or better. for low-voltage cabling, the solution of choice, where permitted, is EMT which is easy to work with, NEC compliant in most applications, and usually appropriate to the environment. (Note: traveling cable, connecting an elevator car to the outside world, cannot be in raceway and accordingly is exempted.)

A number of other exceptions also exist. for example, in an elevator hoistway cables, used in Class 2 power-limited circuits, can be installed between risers and signaling equipment and operating devices, as long as they are supported and protected from physical damage, and are jacketed and flame retardant.

It is necessary to consult the Code regarding requirements for specific jobs. Don't forget any local regulations, which may be more stringent, and also any specialized documents such as NFPA 72-2007, the National fire Alarm Code.

As we have seen MC or better and/or raceways are required in certain instances. Moreover, installers and designers are under the obligation to use their own judgment and to exceed the Code at times, such as where unusual conditions could compromise the functionality or safety of any given cabling situation. For that and other reasons, it is well to consider installing remote control, signaling and communication cabling in EMT even where not required. One advantage is that a very neat and efficient appearance is achieved. Also, cable in raceway is not considered accessible so it doesn't have to be removed if discontinued. If it is deemed desirable to remove such cable, it is easy to pull out and collateral damage to live circuits will not occur.

You may decide to employ Category 5e to network several computers. For a future upgrade to Category 6 or optical fiver, either of these can easily be put in service using the old wire as a pull rope. Once you install the original raceway, the hard work is done.

--END--

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This site is created and conducted By David Herres, NH Master Electrician License #11335M

E-mail: electriciansparadise@hughes.net


HOME | Best Web Host | Question of the Week | Archived Questions | More Archived NEC Questions | Still More Archived Questions | Still More Archived Questions-2 | Still More Archived Questions-3 | Articles | Electrical Deficiencies | More Electrical Deficiencies | Electricians Tools | Online computers | Cybercorner | Electrician's License | Electronics Tutorials | Electricians' worksaving ideas | Electronic Theorems | Satellite Dish | Digital Cameras and Equipment | HTML Color Chart | Electronic Acronyms | Electronic Definitions | Electrician's Soldering Tutorial | Photovoltaic Power | Wind Power | Fire Alarm Basics | More Fire Alarm Info | Working with MC and EMT | Electricians' Color Code | Wiring Commercial Garages | Managing Your Emergency Lights | Lighting Design | Industrial Wiring | Wiring Ethernet | Residential Wiring | Low Voltage Wiring | PLC Overview | Electrical Troubleshooting Techniques | Using Loop Impedance Meter | Ten Common Grounding Errors |NEC and Low-Voltage Wiring | Raceway Protection and NEC | Working with Metal Raceway | Inductance and Characteristic Impedance | Understanding Capacitance | History of the Ethernet | Twisting Data Conductors | NEC Article 800, Communications Circuits | NEC Article 810, Radio and Television Equipment | NEC Article 820, Community Antenna and Radio Distribution Equipment | NEC Article 830, Network-Powered Broadband | Troubleshooting Submersible Well Pumps | Wiring Healthcare Facilities | First Edition National Electrical Code 1897 | Books for Electricians | Links


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