Electrical

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Electrical Design and Drawings

Chapter 31, pages 616-644 (Architecture Drafting and Design, 7th Edition - Donald E. Hepler, Paul Rosss Wallach & Dana J. Hepler. Glencoe McGraw-Hill. 1998.)

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The design and function of any structure is improved through good electrical planning.

Electrical Principles
Power Distribution
Electrical Measurements
Service Entrance
Service Distribution
Branch Circuits
Ground-Fault Circuit Interrupter (GFCI)
Electrical Conductors
Calculating Total System Requirements
Lighting Design
Light Measurements
Types of Lighting
Light Distribution
Reflection
Structural Light Fixtures
 
Developing and Drawing Electrical Plans
Fixture and Device Selection
Switches
Electrical Outlets and Receptacles
 
Electrical Working Drawings
Electrical Symbols
Electronic Systems
Electronic System Drawings
The Complete Plan
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Electrical Principles

  Understanding electrical principles is vital to designing safe and efficient architectural electrical systems

Power Distribution

Electric power is generated from several sources of energy: wind, water, nuclear, fossil fuel, solar (photovoltaic), and solar energy directly into an electric current. All other energy sources are harnessed to produce a rotary mechanical motion that drives electrical generators. The generators convert movement into electricity. Transformers are used to "step up" (increase) the electrical power to very high voltages (hundreds of thousands of volts) for transmission by wires over long distances. Wherever the transmission lines enter an industrial or residential community for local power distribution, large transformers are used to "step down" the voltage to a few thousand volts. Smaller transformers set on poles or in underground vaults are used for final distribution to small groups of ho8uses or individual factories. Usually 110 and 220 volts are delivered to residences.

Electrical Measurements

Electrical properties can be measured with instruments. The terms used to describe units of electricity -- volt, ampere, and watt-- are used in both metric and customary systems.

A volt is the unit of electrical pressure or potential. This pressure makes electricity flow through a wire. For a particular electrical load, the higher the voltage, the greater will be the amount of electricity that will flow.

The term for flow of electricity is current. An ampere, or amp, is the unit used to measure the magnitude of an electric current. An ampere is defined as the specific quantity of electrons passing a point in one second. The amount of current, in amperes, that will flow through a circuit must be known in order to determine proper wire sizes and the current rating of circuit breakers and fuses.

The amount of power required to light lamps, heat water, turn motors, and do all types of work is measured in watts. Wattage depends on both potential and current. Current (in amperes) multiplied by potential (in volts) equals power (in watts).
                amperes x volts = watts

The actual energy used (the watts utilized) for work performed is the basis for figuring the cost of electricity. The unit used to measure the consumption of electrical energy is the kilowatt-hour. A kilowatt is 1000 watts. An hour, of course, is a unit of time. A 1000-watt hand iron operating for one hour consumes one kilowatt-hour (1 kWh). The device used to measure the kilowatt-hours consumed in the watt-hour meter.

Electricity flowing through a material always meets with some resistance. Materials such as wood, glass, and plastic have a high resistance. They are good insulators. Copper, aluminum, and silver have low resistance and are therefore good conductors of electricity. Most electrical

I = E  or   = IR  or R =

R = R =   
R =  12 ohms

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Service Entrance

Power is supplied to a building through a service entrance. Three heavy wires, together called the drop, extend from a utility pole or an underground source to the structure. These wires are twisted into a cable. At the building, overhead wires are fastened to the structure and spliced to service entrance wires that enter a conduit through a service head, as shown in Figure 31-1

In planning overhead service drop paths, minimum height requirements for connector lines must be carefully followed. See Figure 31-2. If these distances cannot be maintained, rigid conduit, electrical metallic tubing, or busways (channels, ducts) must be used.

If the service is supplied underground, three wires are placed in a rigid conduit. An underground service conduit is brought to the meter socket. An underground service entrance includes a watt-hour meter, main breaker, and lightning protection. Automatic brownout equipment is also required by many codes for new construction. All electrical systems must be grounded through the service entrance.

Service Distribution

Electrical current is delivered throughout a building through a distribution panel, or service panel. See Fig. 31-3. The size of a distribution panel (in amperes) is determined by the total load requirements (watts) of the entire building. Watts can be converted to amperes by dividing the total (and future) watts needed by the amount of voltage delivered to the distribution box:

Formula: = amperes

W = metric symbol for watts
V = metric symbol for volts
A = metric symbol for amperes

Example:  = 145 A

Most residences require a distribution panel with a capacity of 100 to 200 amps. The National Electrical Code (NEC) minimum for new residential construction is 60 amps. To compute the total load requirements, the watts needed for each circuit must first be determined.

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Branch Circuits

From the distribution panel, electricity is routed to the rest of the building through branch circuits. A circuit is a circular path that electricity follows from the power supply source to a light, appliance, or other electrical device and back again to the power supply source. See Fig. 31-4. If the electrical load for an entire building were placed on one circuit, overloading 3would leave the entire building without power. Thus branch circuits are used. Each circuit delivers electricity to a limited number of outlets or devices.

Each circuit is protected with a circuit breaker. A circuit breaker is a device that opens (disconnects) a circuit when the current exceeds a certain amount. Without a circuit breaker, excessive electrical loads could cause the wiring to overhead and start a fire. When a breaker opens, or "trips," the power to the branch circuit is disconnected. Similarly, if the sum of the current drawn by the branch circuits exceeds the rating of the main circuit breaker, the main breaker will trip. This protects the service-entrance wires and equipment from overheating and damage. Older homes often have ruses instead of circuit breakers. They serve the same purpose, but overloaded fuses must be replaced. Circuit breakers that trip can be reset.

Branch circuits are divided into three types by the National Electrical Code: lighting circuits, small-appliance circuits, and individual circuits.

LIGHTING CIRCUITS: Lighting circuits are connected to lighting outlets for the entire building. Different lights in each room are usually on different circuits so that if one circuit breaker trips, the room will not be in total darkness.

In all dwellings other than hotels, the NEC requires a minimum general lighting load of 3 watts per square foot of floor space. However, the amount of wattage demanded at one time (demand factor) is calculated at 100 percent only for the first 3000 watts; 35 percent is used for the second 17,000 watts; and 25 percent is used for commercial demands over 120,000 watts. Thus, the general lighting load planned for a 1500 sq. ft. house would be 3525 watts, not the full 4500 watts. It is calculated as follows:

1500 ft. x 3 W = 4500 W (uncalculated amount)

First 3000 W x 100% =  3000 W
Next 1500 W x 35% = 525 W
TOTAL 4500 W       3525 W

If each branch circuit can supply on 2400 watts 9120 V x 20 A = 2400 W), a 1500 sq. ft. house should have two 1860-watt general lighting circuits. See Fig. 31-5. Lighting circuits are also used for small devices such as clocks and radios. However, since all lights and other items on the circuit are probably not going to be used at the same time, it is not necessary to provide a service capable of supplying the full load.

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SMALL-APPLIANCE CIRCUITS: These circuits provide power to outlets wherever small appliances are likely to be connected. Small appliances include items such as toasters, electric skillets, irons, electric shavers, portable tools, and computers. Appliance circuits are not designed to also support lighting needs. See Fig. 31-6 (a & b). The NEC requires a minimum of two small appliance circuits in a residence. Each circuit is usually computed as a 1500-watt load.

  

INDIVIDUAL CIRCUITS: Individual dedicated circuits are designed to serve a single large electrical appliance or device, such as electric ranges, automatic heating units, built-in electric heaters, and workshop outlets. Large motor-driven appliances, such as washers, garbage disposals, and dishwashers, also use individual circuits. These circuits are designed to provide sufficient power for starting loads. When a motor starts, it needs an extra surge of power to bring it to full speed. This is called a starting load.

A separate circuit (20 amps) is required in a laundry area to provide power for the washing machine and the dryer. Because of the danger of water leakage, a ground-fault circuit interrupter receptacle is recommended.

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Ground-Fault Circuit Interrupter (GFCI)

A CFCI receptacle must be located wherever there is a possibility for people to ground themselves and be shocked by the electrical current flowing through their body to the ground. The purpose of a GFCI receptacle is to cut off the current at the outlet. When the GFCI receptacle senses any change of current, it immediately trips a switch to interrupt the current. It operates faster and is safer than the circuit breaker switch or fuse at the power entry panel. A GFCI valve will trip in 1/40 second when an extremely small current variation (ground fault) of 0.005 amps is reached.

In new construction GFCI receptacles must be located with each convenience outlet near water sources and/or pipes in the bathroom, kitchen, garage, laundry and outdoors. Any receptacle located within 10' or within 15' of the inside of a permanently installed swimming pool must also be wired through a GFCI. GFCIs are also required if outlets are placed in unfinished crawl spaces below grade level.

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Electrical Conductors

Wires used to conduct electricity are classified by the type of wire material, the insulation ma6terial, and the wire size. The size of the wire used in a circuit depends on the current to be carried by the circuit. See Fig. 31-7. Although the meter voltage is 120V and 241V, wiring resistance reduces the voltage at the receptacles to approximately 110Va and 220V. Sizes 6 through 2/0 are used for 240-vold (240V) service entrance and circuits. The exact size depends on the capacity of the service panel. Sizes 10 through 14 are used for 120V and 240V lighting and small appliance circuits. Sizes 16 and 18 are used for low voltage items such as thermostats and doorbells.

A low-voltage switching system may be used to turn on or off any fixture, appliance, or light. Because of the low voltage, extremely small wires are used to hook up the switch to the fixture.

Wire size is critical. If a wire is too small for the current applied, excessive resistance (overload) can result. This may cause the insulation to overheat and break down, causing a potential fire hazard. When selecting or preparing to use appliances, it is important to check the UL (Underwriter's Laboratories) ratings to learn the proper wiring requirements.

Aluminum wire is lighter and less expensive than copper, but many codes apply stricter rules to the use of aluminum for residential work. Insulation is available in flexible metal armored or nonmetal sheathed worm. For underground or exterior exposed wiring, wires must be encased in rigid or flexible metal or PVC (plastic) conduits.

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Calculating Total System Requirements

The installation of the proper size of service entrance equipment and branch circuits are dependent upon the square footage of the residence, number of appliances, lighting, and future expansion allowances. To find the total amp service needed for an entire building, first determine the total number of watts needed for each circuit. Add these to find the total watts needed for the building. For example, to calculate the size of the service entrance for a 2000 sq. ft. residence, list the amount of wattage to be used as follows:

bullet

Lighting circuits (typical)
2000 sq. ft. uses 3 watts per sq. ft = 6,000

bullet

Convenience outlets
2 circuits in service area (1220V x 20A) = 4,800 watts
2 circuits in sleeping area (120V x 20A) = 4,800 watts
2 circuits in living area (120V x 240A) = 4,800 watts

bullet

Dedicated circuits

electric range = 10,000 watts
electric dryer =  5,000 watts
washing machine =  1,000 watts
dishwasher =  1,000 watts
forced air unit =  1,000 watts
electric water heater =  2,000 watts
Total 40,400 watts

To find the required service panel amps needed, divide the total watts by the available voltage (240V)

40,400 watts 166.3 amps

Service panels are available with capacities of 30, 40, 50, 60, 70, 100, 125, 150, 175, and 200 amps. The next highest panel above the required amps should be chosen to allow for future expansion. In this case, the next highest is 175-amp service.

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 Lighting Design

  Functional lighting design must consider the interaction among eyesight, objects, and light sources. Good lighting design provides sufficient but not excessive light. Glare from unshielded bulbs or improperly placed lighting should be avoided. Excessive contrast between light and shadows within the same room should also be avoided, especially in work areas.

For centuries, candles and oil lamps were the major source of artificial light. Although candles continue to function for special effects, the major sources of light today are incandescent and fluorescent lamps. Incandescent lamps have a filament (a very thin wire) that gives off light when heated. Fluorescent lamps have an inner coating that gives off visible light when exposed to ultraviolet light. The ultraviolet light is released by a gas inside the fluorescent tube. Incandescent lamps concentrate the light source, while fluorescent lamps provide linear patterns of light. Fluorescent lamps give a uniform glareless light that is ideal for large working areas. Fluorescent lamps give more light per watt, last seven times longer, and generate less heat than incandescent lamps.

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Light Measurements

Human eyes adapt to varying intensities of light. However, they must be given enough time to adjust slowly to different light levels. Sudden extreme changes of light may cause discomfort.

Light intensity is measured in units called footcandles. A footcandle is equal to the amount of light a candle casts on an object one foot away. See Figure. 31-8. Ten footcandles (10 fc) equals the amount of light that ten candles throw on a surface one foot away. In the metric system, the standard unit of illumination is the lux (lx). One lux is equal to 0.093 fc. To convert footcandles to lux, multiply by 10.764. See Fig. 31-9.

 

Types of Lighting

The three basic types of lighting are general lighting, specific lighting, and decorative lighting. Good examples of all three types of lighting can be found in Part Three of the text.

GENERAL LIGHTING: General lighting provides overall illumination and radiates a comfortable level of brightness for an entire room. See Fig. 31-10. General lighting replaces sunlight and is provided primarily with chandeliers, ceiling or wall-mounted fixtures, and track lights. To avoid contrast and glare, general lighting should be diffused through the use of fixtures that totally hide the light source or that spread light through panels. Close spacing of hanging fixtures also creates diffuse lighting. Another solution is to use adjustable fixtures so that the light can be directed away from eye contact.

Where possible, daylight should be included as a part of the general lighting plan during daylight hours. If adequate window light is not available, the use of skylights should be considered.

The intensity of general lighting should between 5 and 10 fc (54 to 108lx). A higher level of general lighting should be used in the service area and bathrooms. Many general lighting fixtures can also be used for decorative lighting by a connection to dimmer switches.

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SPECIFIC LIGHTING: Light directed to a specific area or located to support a particular task is known as specific, local, or task lighting. See Fig. 31-11. Specific lighting helps in performing such tasks as reading, sewing, shaving, computer work, and home theater viewing. it also adds to the general lighting level. Track lighting and portable lamps provide sources of specific indoor lighting.

DECORATIVE LIGHTING: Bright lights are stimulating, while low levels of light are quieting. Decorative lighting is used to create atmosphere and interest. Indoor decorative lights are often directed on plants, bookshelves, pictures, wall textures, fireplaces, or any architectural feature worthy of emphasis. Some decorative lighting can be used as general lighting through the use of dimmer switches.

Outdoor decorative lighting can be most dramatic. Exterior structural and landscape features can be accented by well-placed lights. Outdoor lighting is used to light and accent wall textures, trees, shrubs, architectural features, pools, fountains, and sculptures. See Fig. 31-12. Outdoor lighting is especially needed to provide a safe view of stairs, walks, and driveways.

Remember to conceal light sources and don't over light. use waterproof devices and an automatic timing device to turn lights on and off.

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Light Distribution

Light from any artificial source can be distributed (dispersed or directed) in five different ways: direct, indirect, semi=direct, semi-indirect, and diffused. See Fig. 31-13. Direct light shines directly on an object from a light source. Indirect light is reflected from surfaces. Simidirect light shines mainly down as direct light, but a small portion of it is directed upward as indirect light. Semi-indirect light is mostly reflected, but some light shines directly. Diffused light is spread evenly in all directions with the light source (bulb) not visible.

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Reflection

All objects absorb and reflect light. Some white surfaces reflect 94 percent of the light that strikes them. Some black surfaces reflect only 2 percent. The remainder of the light is absorbed. All surfaces in a room act as a secondary source of light when light is reflected. Refer again to Fig. 31-10. Excessive reflection causes glare. Glare can be eliminated from this secondary source by using matte (dull) finish surfaces and by avoiding exposed light bulbs. Eliminating excessive glare is essential in designing adequate lighting.

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Structural Light Fixtures

Light fixtures are either portable plug-in lamps or structural fixtures. Structural fixtures are wired and built into a building hard-wired. These must therefore be shown on electrical plans and specifications. Structured fixtures may be located on ceilings, on interior and exterior walls, and on the grounds around the building.

Different light patterns are produced, depending upon the type of light fixture. Figure 31-14 illustrates the types of structural light fixtures described in the following paragraphs.

bulletSoffit lighting is used to direct more light to wall surfaces and to horizontal surfaces, such as kitchen and bath countertops, wall desks, music centers, and computer centers.
bulletCove lighting directs light (usually fluorescent) onto ceiling surfaces and indirectly reflects light into the center of a room. The soffit should hide the fixture from view from any position in the room.
bulletValance lighting directs light upward to the ceiling and down over the wall or window treatment. Valance faceboards can be flat, scalloped, notched, perforated, papered, upholstered, painted, or trimmed with molding.
bulletCornice lighting directs all light downward. It is similar to soffit lighting. except cornice lights are totally exposed at the bottom.

WALL FIXTURES: Wall fixtures are used as a source of general lighting, as well as decorative lighting when attached to a dimmer switch. Wall spotlights or fluorescent fixtures may also be used as task lighting. Wall spotlights for accents, diffusing fixtures for general lighting, and sconces are used extensively on walls. See Fig. 31-15. Vanity lights and fluorescent tube lights are also used on walls as task lighting.

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CEILING FIXTURES: A wide variety of lighting fixtures are designed for ceiling installation. Many optional designs are possible within each type. See Fig. 31-16. Likewise, track-lighting units are available in a variety of shapes, materials, and colors. Because track light units can be moved and rotated, the track should be placed to take full advantage of these features.

When entire ceilings are to be illuminated, fluorescent fixtures are ceiling mounted. Translucent or open mesh panels are suspended below the fixtures. The position of the fixtures should be shown on the electrical plan. The suspended luminous ceiling should be drawn. See Fig. 31-17.

EXTERIOR LIGHTING FIXTURES: Waterproof spotlights, flood lights, and wall bracket lights are used on exterior walls for both general lighting and decorative lighting. See Fig. 31-18. Exterior wall lights are often connected to motion detectors for security purposes. Lighting fixtures are used for landscaping, driveways, and walkways. These fixtures are designed to direct light at any angle to illuminate design features. Some fixtures, such as post lamps (lanterns), are designed to emit light in all directions. Other post (ballard) lights are designed with shields that can be adjusted to direct light 35- degrees or to any smaller segment. Swimming pool lights can also be used effectively for landscape lighting since the entire pool becomes a large light source when illuminated.

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 Developing and Drawing Electrical Plans

  Wiring methods are regulated by building codes, and wiring is approved and installed by licensed electricians. However, wiring plans are prepared by designers. For large structures, a consulting electrical contractor may prepare the final detailed electrical plans. Electrical plans include data on the type and location of all fixtures, devices, switches, and outlets.

Fixture and Device Selection

Before placing fixture locations on a floor plan, the number and type of fixtures needed for each room should be determined and listed. See Fig. 31-19. In addition to lighting fixtures, all electrical or electronic devices should also be listed. This list becomes the basis for developing an electrical fixture and device schedule (Schedules are discussed in Chapter 35.)

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Switches

The number, type, and location of switches depends ont he fixtures and devices. Switches control the flow of electricity to outlets and to individual devices.

TYPES OF SWITCHES: Small-appliance circuits and individual circuits are usually "hot," meaning that electricity is available in the outlet at all times. Lighting circuits, however, may be  either hot or controlled by switches. See Fig. 31-20. Single-pole switches control one fixture, device or outlet. To control lights from two different switches a three-way switching circuit (three wires and two switches) is used. A three-way switching circuit is often installed for the top and bottom of stairways. Many types of switch mechanisms are used to control circuits. See Fig. 31-21.

SWITCH LOCATIONS: Switch symbols are located on floor plans. Connections to the outlet, fixture, or device each controls are shown with a dotted line. See Fig. 31-22. Use the following guidelines in planning switch locations:

  1. Include a switch for all structural fixtures and devices that need to be turned on or off.
  2. Indicate the height of all switches (usually 4' above floor level)
  3. Locate switches on the latch side of doors, no closer that 2 1/2" from the casing. See Fig. 31-23.
  4. Exceptions to the standard should be dimensioned on the plan o5 elevation drawing.
  5. Select the type of switch, switch mechanism, switch plate cover, and type of finish for each switch.
  6. Plan a switch to control at least one light in each room.
  7. Use three-way switches to control lights at the ends of stairwells, halls, and garages.
  8. Locate garage door-closer switches at the house entry and within reach inside the garage door.
  9. Control bedroom lights with a three-way switch at the entry and at the bed.
  10. Use time switches for garage general lighting, bathroom exhaust fans, and heat lights.
  11. Use three-way switches for all large rooms that have two exits. Use four-way switches for rooms with more than two exits.
  12. Use automatic switches on closet and storage areas.
  13. Specify timer switches for pool motors.
  14. Locate safety alarm switches for a security system in the master control unit and in the master bedroom.
  15. Switches for outdoor security lighting (motion detector lights) should be installed on all levels.
  16. Locate switches in all rooms to ensure that a person need not enter or leave a room in the dark.

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Electrical Outlets and Receptacles

The terms outlet and receptacle are often used interchangeably. The NEC defines an outlet as a point in a circuit where other devices can be connected. A recep6tacle is a device (at an outlet box) to which any plug-in extension line, appliance, or device can be connected.

TYPES OF OUTLETS AND RECEPTACLES: Different types of electrical receptacles and outlets serve different functions.

bulletConvenience receptacles are used for small appliances and lamps. These are available in single, double, or multiple-units. See Fig. 31-24.
bulletLighting outlets are for the connection of lampholders, surface-mounted fixtures, flush or recessed fixtures, and all other types of lighting fixtures.
bulletSpecial-purpose receptacles are the connection point of a circuit for only one electrical device.

Special purpose outlets and convenience outlets are connected to hot circuits, while lighting outlets are controlled with a switching device. Remember, ground-fault circuit interrupters (GFCIs) are installed in all outlets and switches located near water sources.

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OUTLET LOCATIONS: The positioning of outlets must be consistent with local codes. In addition to code requirements, the following guidelines should be used for locating outlets:

  1. Outlets (except in the kitchen) should average one every 6' (1.8m) of wall space.
  2. Kitchen appliance outlets should average one every 4' of wall space, be located over countertops, and include at least on countertop outlet between major appliances.
  3. Hall outlets should be placed every 15'.
  4. An outlet should be placed no further than 6' from each room corner, unless a door or built-in feature occupies this space.
  5. GFCI outlets should be placed as described earlier in this chapter.
  6. One switched (not hot) outlet should be provided in each room.
  7. Consider furniture placement and positioning of portable lamps when placing lighting outlets. Room-centered furniture may need floor outlets.
  8. An outlet should be placed on any wall between doors regardless of space.
  9. The height of all outlets should be noted on the electrical plan. Exceptions to standard dimensions should be noted at each outlet or referenced on an interior wall elevation. Normal code height for wall outlets is 12" to 18" from the floor. Countertop heights are normally 4'-0" above the floor line.
  10. All individual outlets should be labeled with the appliance or device served.
  11. At least one outlet should be placed above each bathroom countertop or vanity table. A minimum of two outlets should be in each bathroom.
  12. Provide an outlet for each fixture, device, or appliance in the plan.
  13. An outdoor weatherproof outlet should be provided on each side of a house. Position a waterproof outlet for a patio, pool, and a grill. Position outside outlets for decorative lighting and entry doors, garage, and security lights.

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Electrical Working Drawings

  Complete electrical plans ensure that electrical equipment and wiring are installed exactly as planned. If electrical plans are incomplete and sketchy, the installation depends upon the judgment of the electricians. Designers should not rely upon electricians to design the electrical system, only to install it. Conversely, designers do not plan the position of every wire, only the position and relationship of all fixtures, devices, switches, and controls. This is done with the use of electrical symbols.

Electrical Symbols

Hundreds of electrical symbols are used on floor plans to describe what and where electrical elements will be installed. About sixty symbols apply to residential or light construction. Some of the more commonly used symbols are shown in Fig. 31-25 a-d.

 

Although the wiring diagrams detail how a fixture is wired to a switch, these diagrams are abbreviated on architectural plans. See Fig. 31-26.

Some floor plans are so filled with dimensions, labels, and notes that there is little space for electrical symbols. For this reason, only the wall outlines are traced as an outline for preparing electrical plans. On computer-generated floor plans, this may involve deleting all but the basic wall outline layer.

To draw an electrical plan:

  1. Draw all electrical symbols on an abbreviated floor plan. This will prevent interfering with other lines, letters, and numbers on a complete floor plan. Electrical symbols are added to the plan in their appropriate location. If an exact location is required, this should be dimensioned or shown on a separate elevation or detail.
  2. After all symbols are located on a plan, connect the switches to fixtures or devices by drawing a dashed and curved line from each switch to the outlet, fixture, or device that the switch controls. This line does not represent the actual wiring, only the control link.

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Room Wiring Drawings

Typical architect5ural wiring diagrams identify the various electrical fixtures and devices and trace the control of each fixture to a switch. Wiring plans for various rooms and areas in a house are shown in Fig. 31-27 a-j.

Because many kitchen appliances are heat-producing and therefore require high wattages, kitchen outlets are divided among several circuits. Otherwise, two or more appliances could overload a circuit when used at maximum load. Utility rooms also require heavy-duty outlets for motor-driven and heat-producing appliances. On the other hand, bedrooms, bathrooms, and closets require comparatively low wattage levels. Stairs and halls present special problems in electrical planning. Three-way and four-way switches must be carefully located to provide control at many locations and thus eliminate unnecessary backtracking.

In drawing electrical plans on a CAD system, symbols can be called up from a symbol library and copied into the correct position. Electrical symbols are often added by using the layering function. This enables the symbols to be plotted in a different color or omitted totally from the floor plan.

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Electronic Systems

  Many building systems can now be controlled electronically with computers. Such electronic systems include a centralized computer and control units (touch-screen or keyboard) near entry doors and in the master bedroom. Lights, alarms, safety devices, telephones, and heating and air conditioning units are some examples of building systems that can be controlled electronically. High-technology features that should be considered in the architectural design process are those that:
  1. Monitor smoke, gas, sound, and movement and sound an alarm when established levels are exceeded.
  2. Monitor and adjust heating, cooling, and humidity levels for each room.
  3. Provide videophone intercom communication between entrances and selected rooms, including synthesized voice response to visitors.
  4. Open and close, lock and unlock doors, windows, vents, gates, and vents from a central control center.
  5. Turn on or off appliances, audio systems, or VCRs from a central control center directly or on timed sequences.
  6. Monitor and/or time the opening and closing of solar energy devices, including window shades and drapes.
  7. Control lighting circuits from a central location directly or on timed sequences.
  8. Program combinations of controls to activate systems on a timed basis for night, morning, midday, evening, work week, weekend, or vacation modes of operation.
  9. Are capable of activation via outside, inside, and remote phone commands. Some systems use electronically synthesized voice commands for communication.
  10. Monitor intruder action by body heat (infrared sensors), motion, light interruption, or noise levels to automatically alarm occupants and/or security command center.
  11. Record images for immediate use and future reference with closed-circuit video cameras interfaced with a computer.

Automation systems can be combined, for instance, to automatically dial police and fire departments when sensors are activated. Security companies usually design total security systems as specified by the designer.

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Electronic System Drawings

After outlets and switches are located on floor plans, electronic systems are added with special symbols. The control units and the devices for any combination of these systems may be drawn directly on the electrical plans. Separate system plans may also be prepared.

SECURITY SYSTEMS: Designing security systems involves specifying the locations of controls and of sonic (sound) motion, and heat sensor devices. These locations are drawn on floor plans with special symbols. See Fig. 31-28. Contact devices for security systems, which signal when contact is interrupted, are indicated on door and window symbols. 

SURGE AND LIGHTNING PROTECTION: A power surge can damage or destroy televisions, VCRs, steroes, and computers. Surge protection devices should be provided at the distribution panel for the entire system. Lightning rods (air terminals) can reduce lightning damage by providing a grounding path of least resistance to discharge the electricity. Rods are placed on rooftops and are connected to cables at diagonal corners of a building. The cables extend into the ground, two feed from the foundation.

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COMMUNICATION SYSTEMS: Positions and connections of doorbells, chimes, music, and any communication units need to be included on the floor plan. The bell- or chime-activating button is connected to the unit with a line drawn the same ways as a line connecting a switch to a fixture. Lines also show the connection between intercom master and remote units. Connections of audio devices with remote speakers, or television cables with TV sets and VCRs, are similarly indicated with lines.

INTEGRATED SYSTEMS: Security, communications, and device-control units may be combined into one integrated system. Automated systems can activate particular parts of the integrated system, such as climate control or lighting, on a timed basis. Similarly, remote controls can be used to control any part or all of the system. These remote controls are low-voltage (24 volt) switching systems. The electrical plan should show the position of the master control panel and the remote.

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The Complete Plan

Drawing a complete electrical plan involves all of the input included in the room plans. In addition, lines must be drawn between switches and fixtures which are in different rooms, on different levels, or between the interior and exterior. When a link is made from one drawing to another, the line is labeled with the contact point on the other drawing. This is common bet5ween first-and second-level drawings. See Fig. 31-29. It is also common between interior and exterior links

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