Residential duct sizing guide the following duct sizes are based on a fraction drop of. The velocity reduction method can be used for sizing air ducts. A series of equations is used to determine this, including duct cross sectional area, air flow rate and air speed. The velocity method takes into account the speed at which air flows through the ducts based on their general size. 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. Use duct sizing revit products 2017 autodesk knowledge. Fellow ashrae 0 f the three duct design procedures recommended by the 1997 ashrae handbookfundamentals, only the tmethod incorporates lifecycle cost. What are the different methods for hvac duct sizing. Many times, systems are sized to operate at a certain pressure or not in excess of a certain pressure. Jun 09, 2017 to this point in our little series on duct design, weve been calculating intermediate quantitites.
You can specify sizing for sections of duct using friction andor velocity, equal friction, or static regain sizing methods. Duct sizing and calculation methods revit products 2018. Larger volumes or higher static pressures should be dealt with on an individual. The following duct sizes are based on a fraction drop of. The fundamentals of duct system design mcgill airflow. Many times, systems are sized to operate at a certain pressure or not in excess of. This manual provides the hvac system designer detailed information on duct design and u. The velocity reduction method can be used when sizing air ducts. This is a device that allows the user to input certain calculations about the areas where hvac ducts will be installed, such as air volume and air velocity, and uses that information to output proper supply and return duct sizes. There are many methods for producing acceptable supply duct designs. Duct sizing needs a ductulator or software but this excel calculator performs the same calculations. Over sizing systems cost more and does not maintain the desired air flow and undersized duct work causes the system to strain mechanically and can be noisy. The equal friction method creates an initial estimate for duct sizing based on the constant pressure loss per unit of duct length specified default is 0. In this method, the frictional pressure drop per unit length of duct is maintained constant throughout the duct system.
Pressure drop calculation revit computes pressure losses in ductwork based on the geometry and roughness of the ductwork, air density, and air dynamic viscosity. 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. Both methods were developed as expedient practical procedures and neither addresses optimization. There are three methods used for most modern duct sizing. Today we use all that to find out how big the ducts need to be. Duct sizing, pressure augmentation and size augmentation ips method. 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 16x12 270 20x4 430 18x6 670 18x8 930 18x10 1100. You can let the program size all the ducts for you using three different sizing methods, or enter your own sizes to analyze an existing design. The reader should refer to other publications for information on these sizing methods. This may increase the system cost compared to other methods. Sep 26, 2018 describe duct sizing methods, engineering units, and best practices create content as parametric multiview parts download also. It is necessary to select the main duct velocity consistent with good practice from a standpoint of noise for a particular building or application. The equal friction and static regain methods used in revit use the ashrae duct fitting database, version 5. Higher pressure at the same volume flow rate means that more energy is required from the fan.
Ductwork sizing, calculation and design for efficiency. Select suitable velocities for main and branch ducts from the table below. This procedure can also be used to estimate a basement or attached garage temperature and heat loss or gain to a building through the floor or wall. Describe duct sizing methods, engineering units, and best practices create content as parametric multiview parts download also. The basic principles of duct design, part 1 energy vanguard. Three ways to check duct sizing in the field contracting. Residential duct sizing guide the following duct sizes are based on a friction rate of. Ductsize lets you create a complete duct system from start to finish, and gives you control over every aspect of the design. Design of flexibleduct junction boxes current standards ashrae 2012 hvac systems and equipment, box plenum systems using flexible duct constrains box width to 23x entrance width constrains box length to 2 x box width flat pressure loss 0. Dont kill your air flow with this flex duct disease. This 3hour hvac training online video series provides guidance on how to properly use a friction chart andor accas duct slide rule values for sizing duct in the field.
Ductsize hvac duct sizing and analysis elite software. Increased friction rate in compressed flexible duct. Oct 25, 2015 the equal friction method of sizing ducts is recommended because it does not require a great deal of experience in the selection of proper velocities in the various sections of the duct system. Dec 15, 2017 this video will explain how to use friction chart for determining duct diameter and velocity in each duct. Most duct sizing tables use the roughness factor for smooth, galvanized sheet metal as the reference value. Larger volumes or higher static pressures should be dealt with on an individual job basis. Design air conditioning ducts using velocity method, equal friction method or static regain. This method requires many computations, which makes noncost optimizing techniques more attractive. Principle of duct design in hvac systems cedengineering. The duct sizing utility is designed to follow the equal friction method workflow in computing losses.
Odds are very high that the new equipment wont operate at the efficiency and comfort levels you promised your customers. It is designed for calculating and sizing duct dimensions according to air volume cfm, roughness, velocity, etc. The fourth edition of hvac systems duct design presents the basic methods and procedures required to design hvac air distribution systems. Ductsize hvac duct sizing and analysis duct sizing with full control. Ordinary heating, ventilating, and air conditioning duct systems read air pressures at 0. Higher pressure at the same volume flow rate means that more energy is required from the fan, and this will raise the operating cost.
In a few minutes, even the most complex systems can be sized with a duct sizing slide rule. Heat conduction and thermal resistance for steady state conditions and one dimensional heat transfer, the heat q conducted through a plane wall is given by. The critical paths having maximum pressure loss are addressed by refining flow parameters and fittings in the duct work. Duct sizing equal pressure method on the chart we start by drawing a line from 0. Sizing can be applied to sections of ductwork or to an entire system. You can select a dynamic sizing method for the ductwork for the duct systems in a project using the duct sizing dialog. May 25, 2017 other articles in the duct design series. Starting at the fan discharge, choose the larger duct size from among both of the following design limits. The course concludes with the basic instructions for filling out a manual d speedsheet.
The equal friction method can be done manual or more or less semi automatic with the spreadsheet template below. To use the duct sizing dialog to specify duct size, the ductwork must be. Pressure or pressure loss is important to all duct designs and sizing methods. Jul 11, 2014 the rougher the surface, the higher the friction loss. Full worked example included with cfd simulations to optimise your design to ensure the highest energy efficiency.
Were following the manual d protocol for duct design, a standard developed by the air conditioning contractors of america acca. Quick introduction a good duct design is a balance between. The traditional duct sizing methods are equal friction and static regain ashrae, 2001. In addition to the basic engineering guidelines for the sizing of hvac ductwork. Apr 14, 2020 a third method for hvac duct sizing involves using a device called a ductulator. Three ways to check duct sizing in the field the assumption that duct systems work just fine when replacing equipment will likely get you in trouble sooner or later. The procedure is to be select a suitable velocity in the main duct from the sound level consideration. Duct system design guide first edition 2003 mcgill airflow corporation mcgill airflow corporation one mission park groveport, ohio 43125 duct system design.
The back side of the duct calculator has a conversion table for converting the material roughness from smooth sheet metal to other materials. This equalfriction method of duct sizing should be adequate for normal residential furnace heating and air conditioning applications. Another important factor in the installation process is to make sure the duct work is sized properly. Find the sizes of main and branch ducts from the air flow rates and the velocities by using. Duct systems pressure losses operation cost duct systems acoustics environmental costs, and air balance procedures commissioning costs of these, duct sizing is the simplest. Ductwork sizing, calculation and design for efficiency the. Jul 03, 2018 duct sizing, duct calculation, duct design, energy efficient ductwork design. The summary of loss coefficient run in tandem with duct sizing summary. Duct sizing in revit, air density, air dynamic viscosity, and air flow are used to calculate duct sizing. Jul 15, 2018 duct sizer ductulator for hvac air ducts. Available computer programs are simply automated versions of these manual procedures. Knowing the air flow rate and the velocity in the main duct, the size and friction loss are.
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