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ARTICLE 422 Appliances Article 422 covers electric appliances used in any occupancy. The meat of what you need to know is in Parts II and 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 drive the requirements of Article 422: On the one hand, an appliance should not overload the circuit supplying it, and on the other hand, an appliance should not be supplied with more current than it should reasonably draw. The first concept is why 422.10 specify the minimum circuit protection. The second concept is why 422.11 specify 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 doesn't include "Fixed Electric Space-Heating Equipment" in the scope of Article 422, but instead provides Article 424 to address fixed electrical equipment used for space heating.
ARTICLE 424 Fixed Electric Space-Heating Equipment Many people are surprised when they see how many pages are in Article 424. This is a nine-part article on fixed electric space-heaters. Why so much text for what seems to be a simple application? The answer is Article 424 covers a variety of applications-these heaters come in various configurations for various uses. Not all of these Parts are for the electrician in the field-the requirements in Part IV are for manufacturers. Most electricians should focus on Part III, Part V, and Part VI. Fixed space heaters (wall-mounted, ceiling-mounted, or free-standing) are common. You will find these in many utility buildings and other small structures, as well as in some larger structures. When used to heat floors, space-heating cables address the thermal layering problem typical of forced-air systems-so it's likely you will encounter them. Duct heaters are very common in large office and educational buildings. These provide a distributed heating scheme. Locating the heater in the ductwork, but close to the occupied space, eliminates the waste of transporting heated air through sheet metal routed in unheated spaces. So, it's likely you will encounter those as well. What about the rest of Article 424? Parts I and II are short and self-explanatory. Part VII and Part VIII provide the requirements for boilers-if you're working with electric boilers, study those two Parts. Part IX provides the requirements for heating panels.
ARTICLE 430 Motors, Motor Circuits, and Controllers 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 Part VIII, and air-conditioning and refrigerating equipment are covered in Article 440. Article 430 is by far the longest 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 that they are also inductive loads with a high current demand at startup that is typically six, or more, times the running current. This makes circuit protection and motor protection necessarily different. So don't confuse circuit protection with motor protection-you must calculate and apply them separately. If you remember that as you study Article 430, you will find it much easier to understand and apply.
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 reverse-they produce electricity when rotated, instead of rotating 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 need overload protection, and it's necessary to size the conductors that come 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 System" in Article 100.
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