This air transport system also includes the fan itself, the air. Current duct design methods for variable air volume vav systems are based on the use of peak constant airflow. Rightsizing of a heating, ventilation, and airconditioning hvac system is the selection of. For air quantities greater than 4500 ls size duct at 10ms. The air handler should be located where the shortest duct runs possible are attained. In addition to the basic engineering guidelines for the sizing. University of colorado boulder, co, usa overview system description secondary hvac systems air distribution room diffusers and air terminals duct design fan characteristics air handling units water distribution cooling coils pipes and pumps primary hvac systems electric chillers. Mcgill airflow corporation is the nations foremost producer of sheet metal duct and fitting components for air handling systems. Duct leakage figure 1 can occur on either the supply side or the return side of the air handler as well as in the air handler itself.
The purpose of this project is to develop a costeffective design for moving the hvac system into conditioned space. Design of flexible duct junction boxes conclusions designers must recognize that junction boxes are cost effective but add more pressure to systems compared to trunk and branch designs. This and a companion paper introduce an optimum duct design proce. To this point in our little series on duct design, weve been calculating intermediate quantitites. Pdf duct designing in air conditioning system and its. On t he b asis of a particular air flow and velocity obtained from the previous stage, the a rea of the duct is determined using t he equal fricti on method. A comprehensive duct layout indicating sizes, design airflows, pressure class, and routing of the duct system. Design air conditioning ducts using velocity method, equal friction method or static regain method. For air quantities less than 180 ls, size duct at 4. Duct design fundamentals static pressure ps measure of the static energy of air flowing air which fills a balloon is a good example of static pressure equally exerted in all directions the atmospheric pressure of air is a static pressure 14. Air ducts systems in air conditioning systems the duct is considered a static component of the installation through which air flows within the building,connecting all parts of the system and via which used or exhaust air is discharged.
When sheet metal is to be fabricated into system components, the steelworker sw provides the expertise. This manual provides the duct system designer with the technical information required to design a complete air distribution system. As a utilitiesman ut, you can expect to become involved in the installation of duct andor ventilation systems designed to provide conditioned air or to remove less desirable air from a given space or facility. This text has been extensively revised and updated, and now includes key portions of the previously separate duct design home course study material.
The ansi recognized national standard for residential hvac duct design will help you design a duct system in less time. Lowvelocity design will lead to larger duct sizes, but it may be worth since, doubling of duct diameter. Source book for efficient air duct systems in europe 1 introduction one aim of this source book is to increase hvac designer awareness of the important role the ductwork plays with respect to function, costs and energy use of the hvac system. How are the duct designers, and other participants, working with duct design and requirements today. Explain typical performance characteristics of a duct system. Principle of duct design in hvac systems cedengineering. Ductwork design for most hvac contractors, the mathematics and calculations of good duct sizing and layout are done by applying the accas manuals d residential and q commercial. It is important to note that the duct system is not just the duct work. Choosing the rightsized duct is critical to maintain proper air flow in the system. Consequently, the total pressure or total energy of air flowing in a duct system is generally equal to the sum of the static pressure and the velocity pressure. Any air that does not complete that journey is considered leakage and is wasted. Instead of estimating how large a duct each space needs, technicians measure room volume and layout, enter specifics like floor type, room direction for heat. Ansismacna 0062006 hvac duct construction standards.
Source book for efficient air duct systems in europe. To retrace your path within a pdf document, click the. For air quantities greater than 180 ls, but less than 4500 ls. Design guide for heating, ventilating, and air conditioning systems. However, vav systems operate much of the time at an offpeak load condition and the impact of varying airflow rates to the sizing of duct systems has not been considered. Rules of duct design acca manual d residential duct systems. Thus, ter 16 of the 2004 ashrae handbookhvac systems and. Duct system design vi introduction foreword these reference manuals have been compiled and written by engineers and consultants employed by united mcgill corporation and its subsidiary, mcgill airflow corporation. Duct systems are designed to properly distribute air throughout a building. The air handler is designed to remove air from the house, condition it, and supply it back to each room. The most basic vav box consists of an enclosure with a small air valve damper that regulates the air. Book by sheet metal and air conditioning contractors national association, 2006. All information provided in this document is to be used as a guideline only.
Understanding basic residential ductwork design please note. Ideally these selections hould be made so that all the design constraints are satisfied and the lcc is minimized. Ratna kumari and others published design and drafting of hvac, central air conditioning system for an office building find, read and cite all the research you need on. Principle of duct design in hvac systems polar air. Lowvelocity ductwork design is very important for energy efficiency in air distribution systems. The spiral wire must have corrosionresistant material and be thoroughly checked to ensure its durability and defeat resistance. Duct design quick introduction duct sizing tools and methods recommended duct velocities and noise effects duct fitting pressure losses do and donts of duct design duct applications as 4254.
In this chapter, system design and the calculation of a systems frictional and. The outcome of the duct design process will be a duct system supply and return plenums. The requirements for exhaust air and outdoor supply air for each zone must be established prior to calculating cooling and heating. According to the smacnas hvac systems duct design manual, the static regain. Most bulk solids will require significant air velocity in the ductwork to convey the material in full suspension usually an air velocity of about 4,000 fpm 67. Hvac design overview of variable air volume systems. This document is not a procedural stepbystep set of instructions on how to create a duct design. Ducts that are not well designed result in discomfort, high energy costs, bad air quality, and increased noise levels. Pressures varied significantly with size of box, relative positions of outlets, air velocity and volumetric flow. The purpose of residential ductwork design is to properly distribute the airflow, produced by your heatingcooling system, to your house. The polyvent and isovent air ducts frame is made of highcarbon steel spiral wire with 0.
The secret to moving air efficiently through your duct systemmy article on david hills 2015. Below is a simple model for determining duct sizes. The types of fittings to be used based on the designers calculations of fitting losses i. This manual provides the hvac system designer detailed information on duct design and u. The purpose of a duct system is to transport air from a source the fan to the people or equipment that need air conditioning. Today we use all that to find out how big the ducts need to be. Another aim is to point out the connection and cooperation that is necessary between.
Decisions are made about the types of systems to be used, building zoning, equipment locations, and routing of ductwork. What distinguishes a variable air volume system from other types of air delivery systems is the use of a variable air volume box in the ductwork. Handbook of heating, ventilation and air conditioning. Were following the manual d protocol for duct design, a standard developed by the air conditioning contractors of america acca. The popular and accurate procedure has been revised to include updated and expanded vav guidance, with detailed examples. Duct design 81 introduction 81 pressure head and energy equation 82 friction loss analysis 87 dynamic losses 87 ductwork sectional losses 88 fan system interface 88 pressure changes system 89 duct system design 89 design considerations 812 duct design methods 8 duct design procedures.
Highvelocity hv duct systems are characterized by air velocities in the range of 2500 to 3500 fpm. Dont kill your air flow with this flex duct disease. Smacnas hvac air duct leakage test manual 1985 to verify the intent of the. One disadvantage to locating the air handler in the attic space is serviceability. Installation of ductwork should comply with smacna hvac duct construction. The basic principles of duct design, part 1 energy vanguard. Heating, ventilation, and air conditioning design strategy. Duct design objectives the objectives of good duct design are occupant comfort, proper air distribution, economical heating and cooling system operation, and economical duct installation. Acca manual tair distribution basics for residential and. Design cfm 4 cfm 6 cfm 8 cfm 10 cfm 12 60 6x4 60 4x6 90 4x8 120 4x10 150 4x12 90 8x4 110 6x6 160 6x8 215 6x10 270 6x12 120 10x4 160 8x6 230 8x8 310 8x10 400 8x12 150 12x4 215 10x6 310 10x8 430 10x10 550 10x12 180 14x4 270 12x6 400 12x8 550 12x10 680 12x12 210 16x4 320 14x6 490 14x8 670 14x10 800 14x12 240 18x4 375 16x6 580 16x8 800 16x10 950.
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