The rectangular ducts and fittings are designed with slipfit connections, either welded or button punched. Nominal spiral flat oval duct sizes and round equivalent singlewall flat oval. Pressure loss in piping systems by using the equivalent pipe length method. By using this method of calculating duct pressure loss, the equivalent length of each fitting is added to the total duct length to establish the pressure loss through the duct system. The total pressure change due to friction, fittings, equipment, and net thermal. Duct design fundamentals pressure losses friction equivalent duct sizes for same friction loss shape options most duct systems are originally sized with round ducts. This application is a calculator for calculating equivalent length of fittings and valves. For many reasons head room, available equipment, the designer or engineer may want to use an equivalent rectangular or flat oval size. Frp duct provides an economical solution to your ventilation system.
The ducts and fittings below and above these sizes are available on request. Effective length is the sum of the actual measured length of a duct plus all the equivalent lengths of the various fittings included in a particular duct run say. The chart is arranged with pressure loss per 100 feet of duct length on the horizontal axis. Principle of duct design in hvac systems cedengineering. Acs manufactures the following standard round duct and fittings sized in accordance with the astm d 398292, standard specification for contact molded fiberglass duct and hoods replaces nbs voluntary product standard ps 1569. Duct system design guide first edition 2003 mcgill airflow corporation mcgill airflow corporation one mission park groveport, ohio 43125 duct system design i notice. Resistance and equivalent length of fittings pipe fluid. Determine the maximum acceptable airflow velocity in the main duct. Plenum system is the length of singlesize trunk duct.
Equivalent length of generic fittings in feet screwed fittings flanged fittings hazen williams constants, c clean, new pipe 140 150 140 140 pipe material cast iron and wrought iron copper, glass or brass cement lined steel or iron plastic pvc or abs steel, welded and seamless or interior riveted typical range 80 150 120 150 120 150 80. Where necessary circular equivalent of a flat oval duct for equal airflow, resistance, unequal area fittings, convert a loss coefficient from section o to and length. Friction loss in fittings watts water technologies. Table 1 see below provides dimensional tolerances and minimum metal sheet thickness sizes. Use the equivalent table or equation to find the size of the rectangular duct. The inputs can be adjusted by touch, and installation is automatic. Smc tdc, slipdrive and raw sheet metal connectors, inc. The approach does not consider turbulence and subsequent losses created by different velocities. 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. To maintain reasonably uniform air pressures in the airdistribution system, the length of a singlesize trunk duct should be limited to about 24 feet. Friction loss in fittings valves as an aid, liquid sizing constants cv values are shown for valves. By using this method of calculating duct pressure loss, the equivalent length of each fitting is added to the total duct length to. Duct design 3 total effective length energy vanguard. To establish the equivalent length for a given fitting, the fitting equation is set as being equal to the duct length equation.
When you add up the effective lengths of all the fittings and then add that number to the length of the straight sections in the most restrictive runs in the return and supply ducts, you find the total effective length tel. Measurements of the surface area and the lead time for custom ductwork orders are subej ct to separate arrangements. Equivalent length, l d eq of valves and pipe fittings. Equivalent length method calculating minor pressure loss. These values are defined as the flow rate through the valve required to produce a pressure drop of 1 psi. D e is the circular equivalent of rectangular duct for equal length, fluid resistance and airflow, inch a is the length of one side of duct, inch b is the length adjacent side of duct, inch. The equal friction method for sizing air ducts is often preferred because it is quite easy to use. Equivalent length of fittings and valves the application is best viewed using a resolution of 1024x768 pixels. Tel is the total effective length of the longest supply run and the longest return run.
No part of this work may be reproduced or used in any form or by any means graphic, electronic, or. The pressure loss in fittings is determined using the concept of equivalent length. American ductile iron flanged fittings ansiawwa c110a21. Equivalent round dimension is the diameter of the round duct. Materialthickness astm type length galvanized 26 16 gauge a653 g60g90 1 to 12 10 standard. Resistance and equivalent length of fittings equivalent length of fittings like bends, returns, tees and valves in hot water heating systems equivalent length in feet and meter major loss in ducts, tubes and pipes major loss head loss or pressure loss due to friction in ducts, pipes and tubes. The standard dimensions of ducts and fittings range between mm and 2500 mm for any side length. Fitting losses can be expressed as equivalent length of straight duct. Ceiling plenums, duct chases, and obstructions such as walls and beams often dictate that a certain size duct be used, regardless of whether or not it is the best size from a. Table 3 friction losses through pipe fittings in terms. Pressure drop in fittings head loss in fittings is frequently expressed as the equivalent length of pipe that is added to the straight run of pipe as shown below.
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. Equivalent diameter convert rectangular and oval duct geometry to a equivalent circular diameter online calculator with imperial and siunits. This approach is used most often with the hazenwilliams or mannings equations. This is alnors range of rectangular ducts and fittings for ventilation systems. The lengths of straight sections of duct add up to 36 feet for the supply side and feet for the return side. Where would i find a quick list of equivalent lengths for generic fittings for materials other than steel and cast iron. Fundamentals distribution systems 2 space availability the sizing criteria will often be defined by the space available to run the ductwork figure 1. Table of contents hvac systems duct design fourth edition vii foreword. Fitting equivalent lengths pressure losses in fittings are due to the turbulence created as water flows through the fitting. Often the equivalent length of a fitting can be equal to or longer than the straight duct lengths due to the additional friction of turning air. For calculating pressure drop across a pipe route, we need to calculate the total.
We can look them up in tables, like the one below showing effective lengths for various elbows. Equivalent duct calculator app user guide appendix equivalent round for rectangular. Use 1 to compute the total air volume m 3 s, cfm in the main system. The cerm only gives equivalent length values for steel and cast iron. If d is in ft, then l eq is in ft equivalent length equation. Compute the necessary air volume flow m 3 s, cfm in every room and branch of the system. Table 3 friction losses through pipe fittings in terms of equivalent lengths of standard pipe size of pipe small dia. Eastern sheet metal singlewall flat oval spiral duct and fittings construction standards. Each fitting has an effective length that equates its pressure drop to an equivalent amount of straight duct. Resistance and fittings equivalent length in hot water systems equivalent length of fittings like bends, returns. When you add up the equivalent lengths of all the fittings and then add that number to the length of the straight sections in the most restrictive runs in the return and supply ducts, you find the total effective length tel. Nfpa valves and fittings tables engineered software. Each type, style, and configuration of fittings elbow, angle, takeoff, reducer, diffuser outlet, register boot, etc.
Ordinary heating, ventilating, and air conditioning duct systems read air pressures at 0. Fittings dominate when it comes to using up the available static pressure, so you have to choose them carefully. Standard elbow medium radius elbow long radius elbow 45 elbow tee return bend gate valve open globe valve open angle valve open length of straight pipe giving equivalent resistance flow. This value is the comparison length of this fitting to an equivalent length of straight pipe or duct. Corporate headquarters sheet metal connectors, inc. Then, depending on the c value and the pipe inside diameter in relation to steel schedule 40 inside diameter, there are factors to multiply the equivalent length by. Use this mobile app in the field for quick duct pressure loss calculations. Each fitting has an equivalent length that equates its pressure drop to an equivalent amount of straight duct. The fittings add up to 290 feet and 85 feet respectively.