The HVAC construction drawings generally consist of the following parts, listed in the order they will appear in the HVAC drawing set.12
Legend, Abbreviations, and General Notes The legend, abbreviations, and general notes are usually shown on the first drawing in the HVAC drawing set. Or, for smaller proj- ects, the legend, abbreviations, and general notes can be presented on the first HVAC floor plan drawing. The legend is a listing of the symbols used in the HVAC drawings, abbreviations are a listing of the abbreviations used in the HVAC drawings, and general notes describe the general requirements associated with the HVAC systems.
Floor Plans The HVAC floor plans show the arrangement of the HVAC ductwork and piping distribution systems, as well as the HVAC equipment on each floor of the build- ing. HVAC floor plans will be presented at the same scale as the architectural floor plans. A scale of 1/8 in. = 1 ft is commonly used by architects to present the floor plans for projects exceeding approximately 4,000 ft2. Architects use this scale because 16,000 ft2
of floor space can easily be presented on a 24-in. × 36-in. drawing at 1/8 in. = 1 ft, whereas only about 4,000 ft2 of floor space can be presented on a 24-in. × 36-in. drawing
at ¼ in. = 1 ft. Also, a scale of 1/8 in. = 1 ft is large enough to show the detail that is com- monly required for the HVAC ductwork and piping distribution systems and the HVAC equipment. Areas requiring close coordination between disciplines, or where there is a significant amount of HVAC work, will be presented on large-scale plans (see below).
It is common for HVAC ductwork and HVAC equipment with a ductwork connec- tion (such as VAV terminal units) to be presented on one set of floor plans and for HVAC piping (such as heating water piping) and HVAC equipment with HVAC piping connection (such as VAV terminal units with hot water heating coils or finned-tube radiators) to be shown on a separate set of floor plans. This is done where the HVAC ductwork, HVAC equipment, and HVAC piping, if presented on the same set of floor plans, would be cluttered and difficult to read.
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Sections Sections are usually presented at a ¼ in. = 1 ft scale. These sections are used to clarify the arrangement of HVAC systems in areas where close coordination between disciplines is required or where there is a significant amount of HVAC work involved that cannot be clearly conveyed through the use of floor plans alone, such as at the branch connections to risers in vertical shafts and selected areas within equipment rooms.
Large-Scale Plans Similar to sections, large-scale plans are also presented at a ¼ in. = 1 ft scale and are used for areas where close coordination between disciplines is required or where there is a significant amount of HVAC work involved. Equipment rooms are almost always presented as large-scale plans because of the amount of HVAC work that must be shown and because of the close coordination between disciplines that is required. Because a larger scale is used, it is common for the HVAC ductwork, HVAC equipment, and HVAC piping to be presented on the same large-scale plan. However, if it would provide a clearer presentation, the HVAC ductwork and HVAC equipment can be shown on one large-scale plan while the HVAC piping and HVAC equipment is shown on a separate large-scale plan. Also, it is sometimes necessary to present the HVAC ductwork, HVAC equipment, and HVAC piping at different elevations within equipment rooms on separate large-scale plans when the equipment rooms are higher than one story of the building.
Details Because it is not possible to show all of the details necessary for a proper instal- lation of certain pieces of HVAC equipment on the floor plans or large-scale plans, it is necessary for the HVAC system designer to show this information in equipment connec- tion details. These details will show all of the required ductwork and piping connections, as well as support requirements and miscellaneous appurtenances such as thermometers, pressure gauges, and flexible pipe connectors. Also, it is common for details to be devel- oped that describe miscellaneous items associated with the HVAC systems such as pipe hangers, roof curbs, and penetrations through the building envelope.
Equipment Schedules Equipment schedules are used to present the pertinent informa- tion associated with the HVAC equipment for a project in tabular format. The equip- ment schedules list the identification numbers, capacities, electrical characteristics, dimensions, weights, and manufacturers and model numbers that form the basis of design for the HVAC equipment. Separate schedules are provided for each type of HVAC equipment. For example, all of the pumps for a project will be presented in a pump schedule and all of the air handling units will be presented in an air handling unit schedule.
Diagrams Diagrams of the automatic temperature control (ATC) systems associated with the HVAC systems for a project are necessary to show all of the components that are required to ensure that the HVAC systems operate in accordance with the design intent. A sequence of operation is developed for each ATC diagram to describe how the HVAC system is to perform in all of its modes of operation. A direct digital control (DDC) point list is also prepared for DDC ATC systems. Refer to Chap. 9 for a discus- sion of ATC systems and their associated diagrams and DDC point lists.
For steam, heating water, and chilled water systems, flow diagrams are commonly used to give an overview of the central plant for these systems. These diagrams show all of the HVAC equipment that is required, as well as the arrangement of this
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equipment within the systems. Pipe sizes, flow rates, and the HVAC equipment desig- nations are shown on the flow diagrams. It is not necessary to show every equipment isolation valve, thermometer, pressure gauge, or other equipment appurtenance on the flow diagrams because this information is shown in the equipment connection details. However, it is helpful to show shutoff valves that are used to isolate major portions of each system. These valves will also be shown on the HVAC floor plans or large-scale plans.
Finally, riser diagrams are often employed for projects having three or more stories. These diagrams can be used for piping or ductwork systems to show the sizes of the piping or ductwork risers, flow rates, and the branch connections at each floor of the building.
Endnotes
1. A thermostat is an electrical device that performs an action (such as closing a con- tact) in response to a change in temperature. The term thermostat is used in a generic sense in the earlier chapters of this book to describe the device that controls the space temperature. However, modern space temperature control systems serving occupied areas commonly utilize electronic control systems, which would consist of a space temperature sensor (senses temperature only) that is connected to a con- troller. The controller is the device that actually performs the desired action based upon the input it receives from the space temperature sensor.
2. The building envelope consists of the exterior walls, windows, doors, roofs, and skylights, which enclose the building and separate the indoor environment from the outdoors.
3. The types of air systems are usually finalized after the schematic design submission. Prior to the final selection of the air systems, the simplest type of air systemconstant air volumecan be used to perform the block load HVAC load calculations. Refer to the Design Submissions section in this chapter for more information on the sche- matic design submission and block load HVAC calculations.
4. Dew point is the temperature of moist air below which condensation will occur. The dew point temperature of air gives an indication of the total amount of moisture in the air. The higher the dew point, the more moisture is contained within the air and vice versa.
5. A floor plan is a drawing that depicts a view of a floor, or partial floor, of a building looking vertically downward.
6. A section is a drawing that depicts a view looking horizontally in a certain direc- tion. Sections are identified on the floor plans by a number designation, a reference arrow depicting the direction of the view, and the drawing where the section is presented.
7. The finished ceiling is the underside of the ceiling that is exposed to the finished space.
8. Wide flange steel beams are structural members that are mounted horizontally to support the floors or flat roof of a building. Because they have a section that looks like the letter I, they are sometimes referred to as I-beams. The top and bottom (hori- zontal) portions of the beam are the flanges and the vertical portion of the beam, which joins the flanges, is the web. Roof support beams can also be mounted at an angle for sloped roofs.
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C h a p t e r t w o9. Bar joists are composite members, also mounted horizontally or at an angle, that have an open web.
10. The free area velocity for a louver is the velocity of the air through the total open area (free area) of the louver.
11. The face velocity for a louver is the velocity of the air across the entire face of the louver, which includes the louver blade area and the louver free area.