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CHAPTER 4. EQUIPMENT FOR GENERAL USE
With the first three Chapters behind you, the final Chapter in building a solid foundation in the NEC for general work is Chapter 4. With this Chapter, you will be applying the first three Chapters to general equipment. These first four Chapters follow a natural sequential progression. The next four Chapters5, 6, 7, and 8each build from the first four, but in no particular order. You do not need to understand any of the other "next Chapters" to work with any one of them. But, you do need to understand all of the first four Chapters to properly apply any of the next four.
Chapter 4 has some logical arrangement of its own. Here are the groupings:
These grouping make sense. For example, motors, refrigeration equipment, generators, and transformers are all wound devices and articles concerning them appear one after the other in order.
This logical arrangement of the NEC is something to keep in mind when you "can't find something." You know, for example, that transformers are general equipment. So, you would find the Code requirements in Chapter 4. You know they are wound devices. So, you would find transformer requirements located somewhere near motor requirements. Refrigeration equipment in the NEC means hermetically sealed motors. So, the requirements should logically be located right next to motor requirements. And that's exactly where they are.
Article 400. Flexible Cords and Cables
This Article covers the general requirements, applications, and construction specifications for flexible cords and flexible cables.
The NEC does not consider flexible cords and cables to be "a wiring method." Article 400 applies to the cords and cables in Table 400.4, only. It does not apply to the cables in Chapter 3 (e.g., NM or MC cable).
Always use a cord (and fittings) approved for a given application. For example, use cord approved for a wet location if you are using the cord in a wet location. The jacket material of any cord is tested to maintain its insulation properties and other characteristics only in the environment for which UL (or another certifying body) has approved it
We don't go into detail about Table 400.4, but do take the time to review it. It's not limited to extension cordsthree of the entries are for elevator cords alone. You don't need to memorize this table, but do become aware of what it covers.
Article 402 Fixture Wires
This article covers the general requirements and construction specifications for fixture wires.
A fixture is anything permanently attached to a building and considered part of it. This is a legal definition that everyone from accountants to attorneys must observe for a variety of reasons. The NEC recognizes this by providing special requirements for fixtures. One such requirement is that no fixture wire can be smaller than 18 AWG. Another requirement is fixture wires must be of a type listed in Table 402.3. This table makes up the bulk of Article 402.
Article 404. Switches
The requirements of Article 404 apply to switches of all types, such as snap (toggle) switches, dimmers, fan switches, knife switches, circuit breakers used as switches, and automatic switches. Automatic switches include those used as time clocks and timers, plus switches and circuit breakers used for disconnecting means.
Here are some key points to remember:
Article 406. Receptacles, Cord Connectors, and Attachment Plugs (Caps)
This Article covers the rating, type, and installation of receptacles, cord connectors, and attachment plugs (cord caps). It also addresses their grounding requirements. Some key points to remember include:
Article 408. Switchboards and Panelboards
Article 408 covers the specific requirements for switchboards, panelboards, and distribution boards that control light and power circuits.
Some key points to remember:
Article 410 Luminaires and Lampholders
This article covers luminaires, lampholders, pendants, the wiring and equipment forming part of such lamps, luminaires. This Article is highly detailed, but it's broken down into logical Parts. The first five are sequential, and apply to all luminaires and lampholders: general, location, boxes and covers, supports, and grounding. This is mostly mechanical information, and it's not hard to follow or absorb. Part VI, wiring, ends the sequence. The seventh, ninth, and tenth Parts provide requirements for manufacturers to followuse only equipment that conforms to these requirements. Part VIII provides requirements for installing lampholders. The rest of Article 410 addresses specific types of lighting.
Interestingly, the NEC does not include "Lighting Systems Operating at 30 Volts or Less" as a Part under Article 410, but instead provides Article 411 to address them.
Article 422. Appliances
Article 422 covers electric appliances used in any occupancy. Article 100 contains the definitiontake a moment to review that. The meat of what you need to know is in Part II and Part III. Parts IV and V are primarily for manufacturers, but you should examine appliances for conformance before installing. If the appliance has a label from a recognized labeling authority (e.g., UL), it conforms.
Two concepts driving the requirements of Article 422 are that an appliance not overload the circuit supplying it (on the one hand), and that an appliance not be supplied with more current than it should reasonably draw (on the other hand). The first concept is why 422.10 specifies the minimum circuit protection. The second concept is why 422.11 specifies the maximum circuit protection. As you read through Article 422 requirements, try to think of how each one relates to these two concepts.
Interestingly, the NEC does not include "Fixed Electric Space-Heating Equipment" as a Part under Article 422, but instead provides Article 424 to address fixed electric equipment used for space heating. For the purpose Article 424, heating equipment includes heating cable, unit heaters, boilers, central systems, or other approved fixed electric space-heating equipment. Article 424 does not apply to process heating and room air conditioning.
Article 430. Motors and Motor Control Centers
Article 430 contains the specific rules for conductor sizing, overcurrent protection, control circuit conductors, motor controllers, and disconnecting means. The installation requirements for motor control centers are covered in 110.26(F), and air-conditioning and refrigerating equipment are covered in Article 440.
Article 430 is by far the largest Article in the NEC. It's also the most complex. But then, motors are complex. They are electrical and mechanical devices, but what makes motor applications complex is the fact they are also inductive loads with a high current demand at startup that is typically five times higher than the running current. This makes circuit protection and motor protection necessarily different. So, don't confuse circuit protection with motor protectionyou must calculate and apply them separately. If you will remember that as you study Article 430, you will find it much easier to understand and apply.
Article 440. Air-Conditioning and Refrigerating Equipment
This Article applies to electrically driven air-conditioning and refrigeration equipment that has a hermetic refrigerant motor-compressor. The rules in this Article add to, or amend, the rules in Article 430 and other Articles.
Why the special treatment? Several reasons. First, hermetic motors are not general purpose. They are sized, fitted, and engineered for specific applications. You may have seen the phrase "hermetically sealed" on food containers. Something that is hermetically sealed is airtightno gas can enter it or escape it. These motors are sealed airtight. And that affects what you can expect of the motor in terms of performance and heat dissipation.
Each air conditioner manufacturer (e.g., Carrier, Trane) has the motors for a given air conditioning unit built to their own specifications. Cooling and other characteristics are different from those of non-hermetic motors. For each motor, the manufacturer has worked all of the details out and supplied the correct protection, conductor sizing, and other information on the nameplate. Thus, Article 440 requires you to use the nameplate circuit protection rather than what you might develop from applying Article 430.
The application itselfwith the compressor motor often on the other side of an exterior building wall from the normal power sources so it can exchange heat with free air-poses additional problems the NEC addresses in Article 440.
Three key points to remember so you apply Article 440 correctly are:
Article 445. Generators
This Article contains the electrical installation requirements for generators. These requirements include such things as where generators can be installed, nameplate markings, conductor ampacity, and disconnecting means.
Generators are basically motors that operate in reversethey produce electricity when rotated, instead of producing rotation when supplied with electricity. Article 430, which covers motors, is the largest Article in the NEC. Article 445, which covers generators, is one of the shortest. At first, this might not seem to make sense. But, you don't need to size and protect conductors to a generator. You do need to size and protect them to a motor.
Generators do need overload protection, and you do need to size the conductors coming from the generator. But, these considerations are considerably more straightforward than are the equivalent considerations for motors. Before you study Article 445, take a moment to read the definition of "Separately Derived Source" in Article 100.
Article 450. Transformers
Article 450 opens by saying, "This article covers the installation of all transformers." Then it lists eight exceptions. So, what does Article 450 really cover? Essentially, it covers power transformers, transformer vaults, and most kinds of lighting transformers.
One of the main concerns with transformers is preventing overheating. The NEC does not completely address this issue. In Article 90, we read that the NEC is not a design manual and that it assumes the person using the NEC has a certain level of expertise. Proper transformer selection is an important part of preventing transformer overheating.
The NEC assumes you have already selected a transformer suitable to the load characteristics. For the NEC to tell you how to do that would push the NEC into the realm of the design manual. Article 450 then takes you to the next logical step: providing overcurrent protection and the proper connections. But, Article 450 doesn't stop there. Section 450.9 provides ventilation requirements.
Other general requirements of Article 450 include guarding, grounding, marking, and accessibility. Part II provides specific requirements for different types of transformers, building on the general requirements set forth in Part I. Part III provides the requirements for transformer vaults.
Article 460. Capacitors
This Article covers the installation of capacitors, including those in hazardous (classified) locations as modified by Articles 501 through 503.
Capacitors store energy. Thus, simply disconnecting capacitors doesn't de-energize them. For this reason, the NEC requires a means of discharge to 50V in less than one minute. Capacitors have their own requirements for ampacity, overcurrent protection, disconnecting means, grounding, and marking. The requirements for capacitors under 600V are far less stringent than for capacitors over 600V.
Preceding Article 460 is Article 455, Phase Converters. You might want to read through that, just to see what's there. We do not address it in this book because the typical electrician does not deal with phase converter requirements.
Chapter 4 doesn't end with Article 460. The remaining Articles are also important, but they do not address topics the typical electrician will deal with. These are:
You may want to read through these, just to see what's there. After you finish your study of Article 460, you will have completed your study of the first four Chapters of the NEC. And you will have a solid foundation for applying all of the NEC.
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