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. Preliminary Design Guidelines Ideally, the electrical designer should be involved in the design of the project from the very beginning. It would be best, in many situations, for the electrical designer to be involved in the selection of the site for the project. On a large project, it may be necessary to extend high-voltage lines to the project site and the owner may have to pay part of the cost. The electrical de signer is the person who could best discuss the electrical component of project planning with the power company. All of the utilities (whether sewer, water storm sewer, natural gas lines, and so forth) must be checked to determine if they are near the property and whether they can be brought to the property economically. Such information is needed early in the design stage. Before actually beginning the design layout of the project, the designer will need to accumulate certain information: 1. Determine whether electrical service is available at the site, and what type of system voltage is available (e.g., 120/240 V AC, 1_-3W, 208Y/120 V AC, 3_-4W, and so forth). If service is not available, arrangements must be made with the power company to extend service to the building site. Large projects may require more power or a different system voltage than the existing service can supply. Coordination with the power company is desirable as early in the design stage as possible. Costs that must be paid by the owner should be thoroughly discussed, written, and received by the owner. 2. Obtain a list from the owner of all the types and locations of equipment and appliances to be used in the building that will require electricity. Although the electrical de signer may be aware of electrical requirements for much of the equipment, it may be necessary to find the manufacturer's specifications for certain equipment (e.g., motor sizes, power and system voltage required). 3. Work with the architectural designer to best locate all of the electrical equipment and appliances on the floor plan. On commercial projects, this sometimes takes several meetings with the architects, engineers, consultants, owner's representatives, and manufacturer's representatives. There are times when the type of equipment used and its location must be approved by governmental agencies. 4. Review with the architect where the basic mechanical equipment (e.g., HVAC and plumbing), the service en trance equipment, the power and lighting panels, and the conduit or cable will be located. 5. Discuss with the owners any future plans for changing or expanding the facilities (e.g., remodeling, constructing additions or other buildings, future equipment requirements) and anything else that could potentially affect the size and location of the electrical service. Many times, the service entrance must be sized to anticipate future expansion as well as present building plans. Once the basic information has been gathered, the designer can begin to design the system itself. Basic Design Considerations In electrical design there are numerous possible solutions. Experience guides the designer to a solution that best suits the need of the building occupant. The designer achieves a good solution by: • Observing and evaluating existing installations and adapting them to meet the project requirements • Applying electrical systems theory • Applying Code requirements. Design Guidelines for Common Spaces Convenience Outlets and Switches 1. The number and type of lighting outlets should be fitted to the various seeing tasks. Lighting outlets should be located to meet the desired lighting effects and fixtures to be used. Refer to Section 18. 2. All convenience receptacles on 15 A and 20 A general purpose circuits should be of the grounding type, minimizing the hazard of shock from short circuits. 3. GFCI protection should be provided on convenience receptacles where required by local code (e.g., where the occupant is exposed to water). 4. AFCI protection should be used on convenience receptacles where required by local code (e.g., in bedroom circuits). 5. All rooms that have more than one entrance should be equipped with multiple-switch controls (e.g., two-way or three-way switching) at each principal entrance. Principal entrances are those commonly used for entry to the room when going from a normally lighted to an unlighted condition. If this recommendation would result in the placing of switches controlling the same lighting installation within 8 ft (2.5 m) of each other, multiple-switch controls may not be required. 6. Wall switches should be located at the lockset or latch side of doors or at the traffic side of arches, and within the room or area where the lighting outlets are located. 7. Convenience receptacles in living rooms, bedrooms, dining areas, and other habitable spaces should be placed so that no point along the floor line in any usable wall space is more than 6 ft (1.8 m) from an outlet in that space. Any wall 2 ft (0.6 m) or more in length must have a convenience receptacle. Preferably, convenience receptacles should be located near the ends of a wall space, rather than near the center of the wall, to reduce the likelihood of being concealed behind large pieces of furniture. Outlets should not be placed above electrical baseboards, hot air registers, and hot water or steam registers. The intent is to eliminate cords having to pass over hot or conductive surfaces wherever possible. Building Exterior 1. One or more lighting outlets should be located at or near all exterior entrances. Outlets should be switched or automatically controlled. 2. For each single-family dwelling, at least one duplex receptacle shall be installed outdoors to be readily available from ground level. Weatherproof convenience receptacles should be provided on exterior walls for outside work. GFCI protection is required for outdoor receptacles. 3. One or more outlets may be required for exterior equipment (e.g., swimming pool pump, well pump, and so on). Common Areas and Living Rooms 1. Outlets for ambient and task lighting should be pro vided. General illumination outlets should be wall switch controlled. 2. Convenience receptacles in living areas should be placed so that no point along the floor line in any usable wall space is more than 6 ft (0.6 m) from a receptacle outlet in that space. 3. One or more receptacles for entertainment equipment should be provided at bookcases, shelves, or other suit able locations. 4. When general illumination is to be provided from portable lamps, then at least two separate wall-switched plug-in positions should be provided. These can be provided with two switched regular duplex receptacles or one switched plug-in position in each of two split-receptacle outlets. 5. An outlet for a fireplace may be required. 6. A smoke detector/alarm on a 120 V circuit should be considered. Food Preparation/Kitchen/Cooking Areas 1. Lighting design should provide for ambient and local/task illumination of the work areas, sink, range, counters, and tables. Lighting outlets should be switch controlled. 2. Special purpose receptacles should be provided for all fixed appliances (e.g., range, built-in microwave, exhaust hood, dishwasher, trash disposal unit, waste disposal, and so on). 3. At least two 20 A small appliance circuits for kitchen countertops should be provided. These circuits are in addition to those required for refrigerators, ranges, microwaves, lighting, and so forth. Outlets on these circuits should serve only the kitchen, pantry, and/or dining room areas. The following convenience receptacles should be connected to small appliance circuits: • One receptacle for each 2 linear ft (0.6 m) of work surface face. • At least one receptacle to serve each separate work surface. Any counter-space wider than 12 in should have a convenience receptacle. 4. Convenience receptacles serving countertop areas (e.g., except behind refrigerator and those serving fixed appliances) should be GFCI protected. It’s recommended that receptacles serving countertop areas be split wired. 5. A smoke detector/alarm on a 120 V circuit should be considered. Sleeping Areas/Bedrooms 1. General illumination should be provided from either ceiling or wall outlets, controlled by one or more wall switches. 2. A convenience receptacle should be placed on each side and within 6 ft (1.8 m) of the centerline of each probable individual bed location. Preferably, convenience receptacles should be located near the ends of a wall space, rather than near the center of the wall, to reduce the likelihood of being concealed behind large pieces of furniture. 3. All 120 V branch circuits that supply outlets in dwelling unit bedrooms must be protected by an AFCI device. 4. A smoke detector/alarm must be provided on a 120 V circuit and should be AFCI protected. 5. In master bedrooms, outlets should be considered for a television and entertainment equipment (e.g., DVD/VCR player). 6. In master bedrooms, an outlet for a fireplace may be required. Bathrooms/Restrooms 1. Lighting sources at the mirror should be capable of illuminating both sides of the face. 2. At least one GFCI-protected receptacle within 3 ft of the outside edge of each lavatory basin should be provided. A receptacle that is a part of a bathroom lighting fixture is not typically suitable for this purpose. Placing each bath room on a separate circuit should be considered because of the heavy use and demands of these receptacles. The circuit serving bathrooms should have no other outlets (e.g., it cannot supply power to an outside receptacle or a garage receptacle). Where the 20 A circuit supplies only a single bathroom, it can supply power to outlets for other equipment within the same bathroom (i.e., lighting out lets or an exhaust fan). 3. A wall-switched or timer-operated, built-in ventilating fan capable of providing a minimum of 8 to 10 air changes per hour per water closet (50 cfm/water closet) should be provided where no natural ventilation through windows is included. 4. Wall switches should be located so as not to be readily accessible while standing in the tub or shower stall. Laundry Areas 1. Outlets for fixed lights should be installed to provide illumination of work areas, such as laundry tubs, sorting tables, washing, ironing, and drying centers. Lighting outlets should be wall-switched controlled. 2. In the laundry area, one 20 A receptacle for the clothes washer and a special receptacle for the clothes dryer are required. Outlets for other workstations (e.g., sewing, ironing, repairing, and so on) should be provided. 3. One outlet and one switch for a ventilation fan should be provided. 4. A smoke detector/alarm on a 120 V circuit should be considered. Halls/Corridors 1. Ceiling fixtures should be installed for proper illumination of the entire area with particular attention paid to irregularly shaped spaces. 2. Convenience receptacles in hallways within a dwelling unit should be placed so that no point in the hallway shall be more than 10 ft (1.0 m) from a duplex receptacle as measured by the shortest path that the supply cord of an appliance connected to the receptacle would follow with out passing through an opening fitted with a door (the "vacuum-cleaner" rule). Each hall over 25 ft^2 (2.3 m^2 ) in floor space should have at least one receptacle. 3. In entrance foyers, convenience receptacles should be placed so that no point along the floor line in any usable wall space is more than 10 ft (3.1 m) from a receptacle in that space. Stairways 1. Fixed wall or ceiling lighting outlets should be installed to provide adequate illumination of each stair flight. 2. Outlets should be so arranged that the stair system can be fully illuminated from either floor. 3. A smoke detector/alarm on a 120 V circuit should be considered at the top of the stairs. Utility Rooms 1. Lighting outlets should be placed to illuminate the furnace/boiler area and work area. At least one lighting out let should be wall-switch controlled. 2. Convenience receptacles should be provided. 3. Outlets should be provided for each piece of mechanical equipment requiring electrical connections such as the boiler, chiller, furnace, water pump, or compressor. 4. A special purpose outlet may be required for an electric resistance water heater, and/or an electric-resistance furnace. Shops/Garages 1. Lighting outlets should be placed to illuminate the work areas. Task lighting should be provided above work benches. Lighting outlet should be wall-switch controlled. 2. At least one duplex receptacle should be provided for each space in a garage or carport. 3. Convenience outlets should be provided at workbenches. In garages or near water, these outlets should be GFCI protected. 4. Outlets should be provided for automatic overhear (garage) door operators in the ceiling above each bay. 5. Special purpose outlets should be provided for special equipment such as air compressors, welding equipment, tire changer, dust collection equipment, machining equipment (e.g., Tbl. saws, drill presses, milling machines, lathes, machining centers), and so on. Check with owner on equipment voltage requirements, load, and placement. 6. A smoke detector/alarm on a 120 V circuit should be considered. Storage Rooms/Closets 1. Generally, one lighting outlet for each large closet or storage room should be provided. Where shelving or other conditions make the installation of lights within a closet ineffective or unsafe, convenience receptacles in the adjoining space should be so located as to provide light within the closet. 2. Wall switches or automatic door switches are preferred, but pull switches are acceptable. Electrical/Telecommunications Closets 1. Lighting outlets should be placed to illuminate the area. 2. A minimum of two dedicated convenience receptacles on separate circuits is required. Additional duplex convenience receptacles should be placed at 6 ft (1.8 m) intervals around the perimeter. 3. Rooms should be located away from sources of electro magnetic interference (e.g., transformers, motors, x-ray equipment, induction heaters, arc welders, radios, radar systems, and so forth). 4. Emergency power should be considered and supplied. 5. A smoke detector/alarm on a 120V circuit should be considered. Prev: Occupant Protection Requirements |