Rectangular To Round Duct Transition Calculator










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) from Deflecto connects a round duct to a rectangular duct. 3 " x 10" to rectangular to F. H110mm x L290mm x W130mm x Ø125mm round outlet The Deflecto Rangehood Flue is a full aluminium construction ventilation outlet made for maximum fire and corrosion protection. --Development of rectangular-to-round. If a round duct is required, a rectangular-to-round transition adaptor must be used. Rectangular dimensions from 6 to 24 inches in half inch increments. Features: • Available in a wide range of custom dimensions: round connections for 4, 5, 6, 8, 10, 12, or 14-inch diameter duct; rectangular dimensions from 6 to 24 inches in half-inch increments, depending on the circular. Date: 10/21/2008 at 10:49:23 From: Doctor Peterson Subject: Re: Volume of circular end pyramid Hi, Ravi. 06" on most metal duct calculators FIELD DUCT SIZING CHART Rectangular sheet metal duct =. Rectangular duct is rounded up to the nearest 1/4 inch. I want to calculate: rectangular to round. 8-21), then a transition piece should be developed. As men-tioned earlier, this transition duct was designed by Anderson and Kapoor 3 for their computational study. SKU 753418. III Johnson Controls delivers products, services and solutions consulting engineer who designs a system’s duct work typically calculates damper sizes as part of the overall air distribution system. rectangular ductwork fittings 2. Usually, you can see only the outlet, which is a register covered with grillwork. 7m (Round(diameter 22 ) to rectangular (1. To develop the true length lines, construct the true length triangle XYZ with ZX equal to the vertical height of the transition in the elevation view. It is constructed from all galvanized steel, and has rolled edges for safety. Duct Size Calculator; Commercial. Home » Shop » Plastic Ventilation Duct » 204 x 60 mm Plastic Duct. More detail: - When you open the model, you will be prompted top open either the "generic" (formed) model, or the flat_pattern_state. If a round duct is required, a rectangular-to-round transition adapter must be used. The damper can be mounted in a vertical duct. 18", respectively. Modified equal friction, incorporating many of the benefits of. If "ASHRAE 2013" is selected, Flexible roughness is 0. All Rheem products meet or exceed rigorous industry and regulatory standards for quality, reliability, efficiency, and air & water quality. Easy online ordering for the ones who get it done along with 24/7 customer service, free technical support & more. The larger return will have less resistance, therefore it will allow more air to pass through. customary system. It allows you to determine either the size of raw material needed or the number of gore sections to fit on your available material. It help you draw HVAC Ducting (2D & 3D): Rectangular, round and flat oval ducting with auto-BOM, auto-labeling, flat sheet development. CHAPTER 2 LAYOUT AND FABRICATION OF SHEET-METAL AND FIBER-GLASS DUCT As a Steelworker you are required to operate sheet-metal tools and to apply basic sheet-metal layout. 'Industrial strength' structures, thick plate. HVAC Systems & Components Heating Ventilating Air Conditioning HVAC. 2 cm) diameter duct. The chart below shows. Alright, Im trying to make a section of ductwork that is a transition from 12x8 square to 8 dia round. While rectangular duct making machines can readily make any duct dimension, standard practice is to use multiples of 1 in. The table below can be used to compare equivalent diameters for rectangular and round circular ducts. 48 gallons) If you have a rectangular shaped storage tank there is a very simple calculation that can give you the number of cubic feet that will fit inside of. Stoddard, Hvac Designer / Detroit, Mich. ductwork length using the approximate feet of equivalent. 6 cm) clearance must exist between the top of the microwave oven and the rectangular to round transition piece so that the damper can open freely and fully. The surface area of ducts in unconditioned spaces is an important factor in determining the amount of loss or gain due to ductwork in the system. HVAC Ducting (2D & 3D): Rectangular, round and flat oval ducting with auto-BOM, auto-labeling, flat sheet development. Based on the air quantity entered for valves in a ventilation system (hereafter called system), DDS-CAD will sum up and calculate air quantity, speed, nominal pressure loss and balancing. Square To Round Software - Free Download Square To Round - Top 4 Download - Top4Download. 18", respectively. 1 Fabricate and install round straight duct 2. A nominal 2 ton system would have 12 to 13 outlets. They provide a comprehensive range of round, rectangular, oval and spiral ductwork, fittings and accessories for residential and commercial construction. It is constructed from all galvanized steel, and has rolled edges for safety. How to develop a Square to Round A true understanding of what "True Length" means and how to find and see true lengths is everything in pattern development by means of triangulation. Rectangular transitions, S offsets, Rectangular duct elbows, Square-to-round, Round tapers, Round tees, Round elbows Use this book as a handy reference or as a textbook to learn all the methods you may need. Flex duct =. Hvac for Beginners: The Typical Trunk and Branch Duct System Good Ducting Practices: Plenums and Return Air Drops More Ductwork Transitions: Rectangular Side Take-offs and Vertical Ells Multiple Duct Fittings in a Duct System. 1 m, and for a round duct: 815 mm in diameter, 22-gage spiral wound duct, and. Can someone direct me or instruct me on how to accomplish this task. Tite Fit, Aluminum Straight Dryer Venting Duct With Transition Fitting, 2" x 6" Rectangular Duct, To Fit 4" Round Duct. Height: remember to add for bending flanges in or out Top: wide x deep scrape: Bottom: wide x deep scrape: offset: at the: offset:. 5-in HVAC Damper Duct Manual Volume Damper with Sleeve. Traverse Surveying - Definition, Types, Methods, Checks. Round spiral duct is the best choice for duct construction, but if you don’t have the room, flat oval is still a better choice than rectangular duct. Duct Length The total length of the duct system, including straight duct, elbows, transitions, and wall or roof caps must not. For each family Rectangular Eccentric Duct Transitions we need to make some preparations, namely we need to put to our parameters two new of them - parameter "e" and "f" these two determine vertical and horizontal offset. We offer a complete line of rectangular to round transitions for spiral pipe. To develop the true length lines, construct the true length triangle XYZ with ZX equal to the vertical height of the transition in the elevation view. The Duct Size Calculator is the result of collaboration between ASHRAE TC 5. options: psp duct. 1”wc or less (or a metal ductulator at *0. 18", respectively. Ductsize - HVAC Duct Sizing and Analysis Duct Sizing - with Full Control. 14 (pi) to get the area of the round duct in square inches -- for example, 16 x 3. If a round duct is required, a rectangular-to-round. x ( ) = Ft. and 3/16" material. If a round duct is required, a rectangular-to-round transition adaptor must be used. --Development of rectangular-to-round. Elbow (for wall venting only) D. A duct system is a network of round or rectangular tubes—generally constructed of sheet metal, fiberglass board, or a flexible plasticand- wire composite—located within the walls, floors, and ceilings. If the duct is relatively small and the change is only in the height of the duct, such as a 12- x 12-inch duct changing to a 12- x 6-inch. III Johnson Controls delivers products, services and solutions consulting engineer who designs a system’s duct work typically calculates damper sizes as part of the overall air distribution system. Rheem Rectangular to Round Transition Downflow 18 Round. Duct Length The total length of the duct system, including straight duct, elbows, transitions, and wall or roof caps must not. TOLL FREE: (800) 327-2247 FAX. Installation Instructions Over the Range Microwave Oven If a rectangular-to-round transition adaptor is used, the bottom corners of the damper will have to be : calculate total equivalent ductwork length using the approximate feet of equivalent length of some typical. x ( ) = Ft. Students will create proper transitions for the changing duct sizes. The application allows you to save the results of calculations (CSV format) and send them by E-mail, Bluetooth, etc. x Transition Adaptor* _ Wall Cap 40 Ft. Top and base are parallel. length of all straight duct sections. The input of the desired size (volume flow, air velocity or dimension) can be selected. Manufacturer of lock-seam, high pressure spiral pipe and fittings. The 1 piece design offers easy installation. Rectangular Ductwork, Plenums, and Takeoffs Select from the menu below to view any of our product lines. Online Ductulator Free Duct Size Calculator. HVAC Layout & Design. The design factor, calculated from the above formula, and the required airflow (CFM) are then used in a duct calculator to determine the size of all supply and return duct. The Eastern Sheet Metal Equivalent Round Duct Calculator app allows sheet metal contractors and installers, as well as heating, ventilation and air-conditioning (HVAC) engineers and contractors, to convert the dimensions of rectangular and flat oval ducts to round. All Rheem products meet or exceed rigorous industry and regulatory standards for quality, reliability, efficiency, and air & water quality. Flex duct =. This article includes the definition of traverse surveying along with its classification, errors in traversing, checks, the completed method of traversing and plotting of traverse survey. Ive tried all kinds of methods, but nothing has really gotten me an accurate, realistic model. ABSTRACT It is a common misconception that the actual R-value of flexible duct is similar to the rated R-value. Click the tabs for more information on the areas you need assistance with. I want to calculate: rectangular to round. If a round duct is required, a rectangular-to-round transition adaptor must be used. condition exists, you will have to develop the piece by. 05" on most metal duct calculator Round metal pipe =. Weight-based labor formulas generally allow 50% more pounds per man-hour for installing round and flat oval spiral duct versus rectangular. Ductulator calculats duct dimensions using equal friction method or velocity method. Tite Fit, Aluminum Straight Dryer Venting Duct With Transition Fitting, 2" x 6" Rectangular Duct, To Fit 4" Round Duct. Click the tabs for more information on the areas you need assistance with. Do not use less than a 6˝ diameter duct Maximum duct length: For satisfactory air movement, the total duct length of 3¼˝ x 10˝ rectangular or 6˝ diameter round duct should not exceed 140 equivalent feet. I need to calculate the surface are of rectangular to round transition when I have these parameters:. 10 Example. The chart below shows you how to calculate total equivalent ductwork length. Similar to the Taper pattern, it often has a double offset, in which case it is essential to understand which offset dimensions are being requested, and how to change them if necessary. The surface area of ducts in unconditioned spaces is an important factor in determining the amount of loss or gain due to ductwork in the system. The rectangular end I just rivited. ø 4 s x 10 s rectangular or 6 s diameter round duct should QRW H[FHHG HTXLYDOHQW IHHW Elbows, transitions, wall and roof caps, etc. Download the User Guide The Eastern Sheet Metal Rectangle to Round Duct Calculator App is used by sheet metal contractors and installers, HVAC engineers and contractors to quickly convert the following duct diameters: rectangular to round, oval to round, or rectangular to oval using the U. In the second. A symmetrical rectangle to round transition. -Transition piece connecting two circular pipes-parallel joints OBLIQUE JOINTS. condition exists, you will have to develop the piece by. Find duct transitions & connectors at Lowe's today. Round duct diameters are typically limited to multiples of 1 in. Then to get area in meter square, use the equation. I'm looking to create a completely structured (preferably body aligned) grid for a circular-to-rectangular transition duct, i. Maximum duct length: For satisfactory air movement, the total duct length of 31\4 û ! õèæ÷äñêøïäõ òõ & çìäðè÷èõ õòøñç çøæ÷ should not exceed 140 equivalent feet. 6 cm) high Rectangular to Round Transition: NOTE: The minimum 3" (7. Transition Adaptor* Equivalent lengths of duct pieces are based on actual tests and. Provides straight transition from 8" x 10" square to 10" round. Broan 411 - 3-1/4" x 10" to 6" Round Duct Transition - Maximize the air and sound performance of your Broan ventilation fan or range hood using one of our wide vaiety of ducting accessories. Easily connect a 3-1/4 in. – *Assume 66 cfm for 6” flex runs, at 4% compression, with a 4x10 floor or a 6x10 ceiling register. A B C E F D 3" (7. Features: • Available in a wide range of custom dimensions: round connections for 4, 5, 6, 8, 10, 12, or 14-inch diameter duct; rectangular dimensions from 6 to 24 inches in. 14159 r = radius of duct in feet. 4″x 10″rectangular duct. 2, Duct Design, and the Air Distribution Institute. out of 5 stars 2. First, come down the left-hand column until you reach 17 inches; then trace the line horizontally across the columns until you reach the column headed by 16 inches. To find the equivalent diameter for a rectangular duct of specific dimensions, consult a table (Figure 2) or a duct calculator (Figure 3). round vertical duct opening. intersecting lines is 18. i have tried several times and get the same result. D - Diameter (Round Duct) 4 - Transition type. Flex duct =. This consists of frictional losses in the ductwork and dynamic losses in the fittings (bends, splitters, dampers, etc. HVAC Duct fittings included: Duct bends, transitions, tees & wyes, offsets, branches, dampers, diffusers, flexible duct, grills, build-in & customer defined symbols and many accessories…. NOTE: If the existing duct is round, you must use a rectangular-to-round adapter, with a rectangular 3" extension duct installed between the damper assembly and the adapter to prevent the exhaust damper’s sticking. As well as stocking rigid and flexible ducting supplies, grilles and vents, we also have full manufacturing facilities and can provide galvanised rectangular and bespoke metal ducting pieces to suit your needs. 1 Fabricate and install round straight duct 2. 1 Revit side: For each family Rectangular Eccentric Duct Transitions we need to make some preparations, namely we need to put to our parameters two new of them – parameter “e” and “f” these two determine. 8" X 8" thru 24" X 24" New & Improved Heavy-Duty Aluminum rectangular damper w/ Ecojay by Belimo motor Built to stand up to use and abuse SPEC SHEET SHIPPING TIME: 2 Weeks (because. Other Hart & Cooley Mobile Tools. 250] a = length of one side of rectangular duct (inch) b = length of adjacent side of rectangular duct (inch) De= circular equivalent of rectangular duct for equal friction and capacity (inch) Source: 2001 ASHRAE Fundamentals, p. H110mm x L290mm x W130mm x Ø125mm round outlet The Deflecto Rangehood Flue is a full aluminium construction ventilation outlet made for maximum fire and corrosion protection. x ( ) = Ft. Alright, Im trying to make a section of ductwork that is a transition from 12x8 square to 8 dia round. 1 iwc/100′) a 10″ round duct will deliver about 300 cfm. Beauty and health Engineering Finance Life Mathematics Science. DUCT PIECES LENGTH x USED = LENGTH Rectangular-to-Round 5 Ft. In air-delivery ductworks of HVAC systems, pressure losses across duct fittings such as dampers, sensors, bends, transition pieces, duct corners, branches, and even splitter attenuators are important in counteracting the pressure difference created by fans. 003 ft when straight and fully stretched tight at 0% compression (adjusted at other compressions), otherwise the. rectangular to 6 in. Figure 1, which shows the flow visualization measurements of Eckert and Irvine (1956) for an isosceles triangular duct with an apex angle of 11. Date: 10/21/2008 at 10:49:23 From: Doctor Peterson Subject: Re: Volume of circular end pyramid Hi, Ravi. Maximum duct length: For satisfactory air movement, the total duct length of 3 ¼˝ x 10˝ rectangular or 6˝ diameter round duct should not exceed 140 equivalent feet. Duct System Design Guide First Edition ©2003 McGill AirFlow Corporation McGill AirFlow Corporation One Mission Park Groveport, Ohio 43125 Duct System Design i Notice: No part of this work may be reproduced or used in any form or by any means — graphic, electronic, or mechanical, including photocopying,. August 8, 2019, Drawing ductwork transition rectangular to round? I need to morph a rectangle into a circle using push/pull. Rectangular Easy Bend 3-Gore Elbow 90° L. 25 Where • Deq = equivalent diameter • a = one dimension of rectangular duct (inches ) • b = adjacent side of rectangular duct (inches) Equations for Flat Oval Ductwork. 075lb da /ft³). Most people looking for Duct calculator free for pc downloaded: DuctSizer is a tool that can quickly find the correct round, rectangular or oval duct size to fit on your inputs altitude corrected calculations, is a duct sizing calculator that can replaces cardboard duct calculators. Top and base are parallel. Shop Broan Transition in the Duct Reducers department at Lowe's. Can someone here please give me a little insights on making transition pieces? For example, from the heat exchanger opening to the supply duct plenum. standard 3¼˝ x 10˝ rectangular duct. From design and fabrication to finished product assembly, each phase in the manufacturing process is rigorously monitored and measured to ensure the. and the necessary information for the transition of rectangle. Try Now Get Started. As the rectangular duct aspect ratio increases, the relative cost of rectangular over round also increases. 1 Revit side: For each family Rectangular Eccentric Duct Transitions we need to make some preparations, namely we need to put to our parameters two new of them – parameter “e” and “f” these two determine. Details about Galvanized Steel HVAC Transition Duct 6" Dia. It allows you to determine either the size of raw material needed or the number of gore sections to fit on your available material. The kits contain sheet metal pieces and an instructional DVD video to show you how to make sheet metal transitions. If you add an item to the cart, the existing quote items will be removed. The base is a rectangular (different dimensions for length and width). 4″ x 10″ rectangular duct. break point varies by manufacturer). Stoddard, Hvac Designer / Detroit, Mich. 18", respectively. Looking for BROAN Transition Duct, 3 1/4 x 10 to 6" Round Duct Size (In. Pressure vs. How to Calculate Duct Size for an AC System Duct sizing for air conditioning is a complex process using one of three methodologies. spigot or to Domus Ø100mm EasiPipe duct using a 493/494 or 495 connector. The HVAC Ducting module really makes HVAC layout easy. 3¼" x 10" Rectangular Total Ductwork = Ft. Wyes from The Duct Shop are the perfect fitting to use when you need to branch off your duct run to a smaller size. From the half plan view, transfer the plan lengths A1, B1, B2, B3 and Bé4 to the base of the right angle tri- angle and connect the points to apex Z. Each of these pieces are equivalent to a section of straight duct that is longer than their actual physical size. Round to 4" x 10" Rectangular Galvanized Steel HVAC Transition Duct 6" Dia. Duct Size Calculator; Commercial. Item #: 3225-06XX-100000 Brand: Nordfab Model: Condition: Year Mfg: Reg Price: $100. Hot Dipped Galvanized Steel per ASTM A653 CS Type B 28 Gauge Collar height is approximately 2" (4" to 16" diameter) and 3" on 18" diame. A duct run is often kept flat on the top to keep it against the overhead. Your current cart contains a quote. Duct Size (In. Features include: Fully customizable Rectangular, Flat Oval & Round duct Auto-BOM, data listing, pick & match. Full screen Standard. Some items are universal, such as the Biyang Flexible Duct Connector, which can be made in different shapes to fit all kinds of ducts. It is also available within our CAD standalone called AViCAD. If you have any questions about this product and variations available, please refer to the FAQs above or feel free to contact us by phone or email. This tool will calculate the velocity in any units from the specified volumetric flow rate of a substance flowing through a rectangular duct of a defined width and height. Neoprene-coated fiberglass is a cost-effective heating duct that can handle temperatures up to 300°F, which is great for residential ducting systems. The base is a rectangular (different dimensions for length and width). Contact Us: (844) 289-0033 | After Hours Emergency Contact: (800) 217-4698. Ductsize lets you create a complete duct system from start to finish, and gives you control over every aspect of the design. I try to calculate the pressure drop on duct transition lenght around 0. If a round duct is required, a rectangular-to-round. 3 " x 10" to rectangular to F. A 30×8 return grill should be adequate for that, but it depends on the grill. We produce custom ductwork from galvanized steel, stainless steel, aluminum, copper, and other alloys, and have developed a line of galvanized lock-seam pipe in 20-, 22-, and 24-gauge, in 10’ lengths and with diameters from 3” to 14”. I am creating an excel spreadsheet that will calculate me the weights of sheet metal HVAC ductwork and I am creating the equations for weight myself. Online Ductulator Free Duct Size Calculator. x (1) = 5 ft. I draw a rectangle on axis. 7 ms-1 in a rectangular duct 125 x 250mm = 0. Round or oval ducts have advantages over rectangular ducts and this calculator app makes transitions easier. 250] a = length of one side of rectangular duct (inch) b = length of adjacent side of rectangular duct (inch) De= circular equivalent of rectangular duct for equal friction and capacity (inch) Source: 2001 ASHRAE Fundamentals, p. Do not use less than a 6″diameter duct. The Eastern Sheet Metal Equivalent Round Duct Calculator app allows sheet metal contractors and installers, as well as heating, ventilation and air-conditioning (HVAC) engineers and contractors, to convert the dimensions of rectangular and flat oval ducts to round. Fully compatible with AutoCAD, AutoCAD LT, Bricscad, ZWCAD and IntelliCAD. Determine b so that the average velocity in the duct is 20% of ts value in the pipe. It is also available within our CAD standalone called AViCAD. Designing Your Dust Collection System. Is this possible? Currently (for 2d) I just explode the regular rectangular to round transition and stretch it to a certain length. (6″Round) (3. break point varies by manufacturer). This is especially important for projects in which standard duct sizes are not useful, and custom sizes and custom angles for ducts must be produced. 5-in HVAC Damper Duct Manual Volume Damper with Sleeve. Because of this, HVAC professionals and amateurs alike typically don’t calculate the final HVAC ducting size by themselves. Two 6" ducts are (2 x pi r squared) 56. Kair 90 degree ducting straight adaptor with round and rectangular spigots. The other end is a female spigot and fits over Kair 220mm x 90mm Rectangular Duct Pipe (Part: "DUCVKC5704"). round duct with insulation takes up 18 in. Media Contact: Allen Haynes 404. The design factor, calculated from the above formula, and the required airflow (CFM) are then used in a duct calculator to determine the size of all supply and return duct. Straight Duct 12 Ft. Your current cart contains a quote. HVAC Rectangular to Round Duct Equivalents Chart. Mech-Q Ducting is an add-on for AutoCAD, Bricscad and IntelliCAD. • The following equations calculate the round duct diameter that will give the same friction loss as the rectangular or flat oval duct, at the same volume flow rate (cfm). This page continues our discussion of ductwork transitions. In most cases the air in a duct is assumed to be incompressible, an assumption that overlooks the change of air density that occurs as a result of pressure loss and flow in the ductwork. More detail: - When you open the model, you will be prompted top open either the "generic" (formed) model, or the flat_pattern_state. Shop Broan Transition in the Duct Reducers department at Lowe's. Angle or flat bar flanges available; When ordering please quote diameter B and A and B. Online calculator duct. I pull it up a couple of inches. Duct Size Calculator; Commercial. When calculating your duct. Question asked by 1-DLF353 on Jun 11, 2010 Latest reply on Jun 18, I am trying to build a universal design with criteria which will calculate an accurate flat pattern. Available in malleable, zinc and steel, and with features like captive, deep-slot, tri-drive screws and more, Bridgeport products are the best choice for unparalleled field performance. Round to 4" x 10" Rectangular Galvanized Steel HVAC Transition Duct 6" Dia. If a round duct is required, a rectangular-to-round. The Eastern Sheet Metal Rectangle to Round Duct Calculator App is used by sheet metal contractors and installers, HVAC engineers and contractors to quickly convert the following duct diameters: rectangular to round, oval to round, or rectangular to oval using the U. 1 m, and for a round duct: 815 mm in diameter, 22-gage spiral wound duct, and. Step 5 Select a size of square duct that has the same area. 5-in HVAC Damper Duct Manual Volume Damper with Sleeve. Nordfab rectangular to round transitions are ideal for transitioning round to rectangular ductwork or for use as a hood. Always stagger take-off ducts by 12" to maintain pressure. Maximum duct length: For satisfactory air movement, the total duct length of 3 ¼" x 10" rectangular or 6" diameter round duct should not exceed 140 equivalent feet. If a round duct is required, a rectangular-to-round transition adaptor must be used. Learn more With more than 57,000 members from over 132 nations, ASHRAE is a diverse organization dedicated to advancing the arts and sciences of heating, ventilation, air conditioning and refrigeration to serve. TRANSITIONS. 43 m3s-1 17. Broan 411 - 3-1/4" x 10" to 6" Round Duct Transition - Maximize the air and sound performance of your Broan ventilation fan or range hood using one of our wide vaiety of ducting accessories. Duct Size Calculator. If the duct is relatively small and the change is only in the height of the duct, such as a 12- x 12-inch duct changing to a 12- x 6-inch. Fluids Conveying - transitions and transformers. Rectangle to Round (Concentric) Revision 2. Duct Calculator App for iPhone and iPad. The app is available for Apple and Android systems. round to rectangular. Flat oval 3. At a 3-1 ratio, rectangular duct cost about twice as much as round. Find duct transitions & connectors at Lowe's today. Top and base are parallel. If a round duct is required, a rectangular-to-round transition adaptor must be used. 14 = 314 square cm (16 x 3. Rectangular to Round Transition for Roof Venting NOTE: The minimum 3" (7. A sheet metal transition is a custom fabricated duct to connect a new furnace or air hander to existing ductwork. at a 15 degree angle. Suits rectangular outlets L290mm x W130mm or less. What measurements are required to make a transition piece? I've spent 2. 003 ft when straight and fully stretched tight at 0% compression (adjusted at other compressions), otherwise the. Duct Size Calculator; Commercial. x (1) = 5 ft. The chart below shows. the duct transition pressure drop - HVAC/R engineering - Eng-Tips. Round and oval duct have lower initial installed costs than rectangular duct. Here we take you step by step in developing a Square to Round, just keep in mind "Practice makes perfect". Duct System Design Guide First Edition ©2003 McGill AirFlow Corporation McGill AirFlow Corporation One Mission Park Groveport, Ohio 43125 Duct System Design i Notice: No part of this work may be reproduced or used in any form or by any means — graphic, electronic, or mechanical, including photocopying,. For duct sizes not exceeding 24" high by 48" wide, Class2" wide by 11/ 2" deep hangers of 22 gauge sheet metal on 4 foot (max. Beauty and health Engineering Finance Life Mathematics Science. 5 years as a helper to now a G2 mechanic mostly performing PM's and servicing, never had the chance to learn about. And it shows the velocity and/or static pressure loss of air for both types of duct shape. the round duct than the rectangular one. Duct Size Calculator. Is there any way of creating a square to round eccentric duct transition. Calculate the pressure drop in each duct section. Duct shape options include rectangular, round and flat oval. Shop duct transitions & connectors and a variety of heating & cooling products online at Lowes. --Development of rectangular-to-round. Weight UPC Item Code (050206) TTO6 6" 10 11. Rectangular Duct & Fittings "L" Section Duct; Large Section Rectangle Ductwork; Turning Vanes Rectangle Section; Square To Round Transition; Rectangular Elbow; Large Elbow Takeoff; Roof Curbs & Curb Adapters; Commercial Duct Installation; Custom Duct Transition Plenum; Long Way Elbows; Welded Seam Flanged. Formula: d h = 2 × a × b/a + b. Flex duct =. Welcome to the US Duct online resource library. Do not use a duct with a diameter less than 6”. While designing ductwork, it is important for engineers and ductwork manufacturers to geometrically construct the three-dimensional duct from a two-dimensional piece of sheet metal. Stewarts and Lloyds is a leading supplier of quality steel and tube products, pipes and fittings, valves, pumps, irrigation, fencing and hardware products. Hi, I've got two 6" round ducts in a closet that are taking up too much room. the triangulation method. Other Hart & Cooley Mobile Tools. ATLANTA (Dec. Your current cart contains a quote. there are several reasons for specifying round ductwork. 4 cm) rectangular or 6" (15. 7m (Round(diameter 22 ) to rectangular (1. The 1 piece design offers easy installation. Other Ductwork Related Pages. rectangular to 6 in. Get free shipping on qualified Transitions & Connectors or Buy Online Pick Up in Store today in the Heating, Venting & Cooling department. More detail: - When you open the model, you will be prompted top open either the "generic" (formed) model, or the flat_pattern_state. Ductstore is an online store that aims to provide a simple and accessible way of purchasing ventilation and ducting supplies. A nominal 2 ton system would have 12 to 13 outlets. Can someone direct me or instruct me on how to accomplish this task. Figure 12-52. Some items are universal, such as the Biyang Flexible Duct Connector, which can be made in different shapes to fit all kinds of ducts. SKU 753418. Beckfeld, M. It calculates both rectangular and round duct dimensions. , and Chen, Q. Flat oval 3. 4″ x 10″ rectangular duct. Line B1 will equal lines B7, 07, D13. In round ductwork, the law of conservation of mass means a duct diameter can be recalculated for a new air velocity using the simple equation:. ø 4 s x 10 s rectangular or 6 s diameter round duct should QRW H[FHHG HTXLYDOHQW IHHW Elbows, transitions, wall and roof caps, etc. Read Round Duct Diameter (inches) and Friction Loss Per 100' of duct (inches of water). • Tacky gasket provides excellent seal. To find the equivalent diameter for a rectangular duct of specific dimensions, consult a table (Figure 2) or a duct calculator (Figure 3). Two 6" ducts are (2 x pi r squared) 56. Rectangular 4. It makes the proper transition from 3-1/4 in. calculate size for round duct : accept the detected flow value for Flow Rate, or enter a flow value for Flow Rate. A duct run is often kept flat on the top to keep it against the overhead. Hvac for Beginners: The Typical Trunk and Branch Duct System Good Ducting Practices: Plenums and Return Air Drops More Ductwork Transitions: Rectangular Side Take-offs and Vertical Ells Multiple Duct Fittings in a Duct System. customary system. rectangular ductwork fittings 2. Mech-Q Ducting is an add-on for AutoCAD, Bricscad and IntelliCAD. Their measurements showed that those two sizes of oval duct are equivalent to round duct at 5. Need help? Call us! 704-391-6000. the structure appears warped. I need to calculate the surface are of rectangular to round transition when I have these parameters:. It is constructed from all galvanized steel, and has rolled edges for safety. 3 Duct Length and Quantity of Fittings and Dampers. We invited Bob Schmahl to give us a few pointers. Every forced air duct system consists of many transitions, from rectangular to round, from trunk lines to branch lines, from the plenum to the main supply trunks, from the main return air trunk to the return air drop. 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: q = kA(t1 - t2) L Btu hr (Eq. A rectangle to round transition where the round may be offset from the rectangle. The damper can be mounted in a vertical duct. Ive tried all kinds of methods, but nothing has really gotten me an accurate, realistic model. 7 out of 5 stars 5. Broan 3-1/4 in. Do not use this item for any installation or repair of potable water applications. 5" wide x 4. The Eastern Sheet Metal Equivalent Round Duct Calculator app allows sheet metal contractors and installers, as well as heating, ventilation and air-conditioning (HVAC) engineers and contractors, to convert the dimensions of rectangular and flat oval ducts to round. round duct using this Broan 412H 3-1/4 in. Maximum duct length: For satisfactory air movement, the total duct length of 31\4 û ! õèæ÷äñêøïäõ òõ & çìäðè÷èõ õòøñç çøæ÷ should not exceed 140 equivalent feet. The head loss calculator below is based on formula (1):. This app is design to Square to Round or Rectangular to Round shape, Round to Square or Round to Rectangular Shape, Pyramid Shape, Truncated Pyramid Shape layouts Development for fabrication purpose. Corona, CA 92882; California. Corona, CA 92882; California. duct with insulation is only 14 in. 2 Return Air Duct Installation Sizes (Based on. 3 Fabricate and install round ductwork 2. Calculate the pressure drop in each duct section. These products are used for warm air return, supply, and exhaust systems. Can someone help to advise me. If a round duct is required, a rectangular-to-round. A transition connects square or rectangular duct to a round pipe or round flexible duct. DUCT LENGTH The total length of the duct system, including straight duct, elbows, transitions, wall or roof caps must not. 86 m3s-1 22. Equivalent Duct Calculator. Rectangular, Flat Oval & Round duct; Mitre, radius, square throat, dual radius… Auto-BOM, data listing, pick & match. It is constructed from all galvanized steel, and has rolled edges for safety. x ( ) = Ft. Elbow (for wall venting only) D. 07" on most metal duct calculators Step One - Identify the volume of air that will be passing through the duct. 14 = 314 square cm (16 x 3. recommended operating temperature the surface treatment 80°C. Round spiral duct is the best choice for duct construction, but if you don't have the room, flat oval is still a better choice than rectangular duct. Rectangular to Round Transition ROGD Priming and top coating RAL 7032, 50 microns, zinc content 70%. SheetMetalGuy. at a 15 degree angle. 06" on most metal duct calculators FIELD DUCT SIZING CHART Rectangular sheet metal duct =. In this chapter we deal with nominal and balanced pressure loss calculation, and automatic dimensioning of duct systems Principles. The corners of the entrance to the duct are slightly rounded to provide the smooth. (51 mm) in large diameter ducts (actual. When the duct is rectangular there are comparison tables where the different aspect ratios or dimensions are compared to a round duct that would be equivalent. 6 lb 931141 RSC7X6 6" 6 7 lb 931660 Top Take-Offs • For transition from air plenums or rectangular duct to round pipe or insulated flexible duct. Welcome to the US Duct online resource library. Can someone direct me or instruct me on how to accomplish this task. See “Rectangular to Round Transition” illustration. In a well designed system (friction rate = 0. Oval Pipe & Oval Fittings Select from the menu below to view any of our product lines. Friction Loss Calculator for Sheet Metal Ducts. transition adaptor must be used. Therefore, if you use an equal area conversion from round to. These rectangular ducts are used as the main trunk line run for your home's ducting system. We need also add our Sherd Parameter - "Area". Now available with 2-D & 3-D (solid) capabilities. Home » Shop » Plastic Ventilation Duct » 204 x 60 mm Plastic Duct. WxH WxH WxH WxH WxH WxH WxH WxH 80 6x6 7x5 9x4 90 7x6 8x5 10x4 100 7 8x6 9x5 11x4 125 7x7 9x6 11x5 13x4 150 8x7 9x6 12x5 15x4 175 8 8x8 9x7 10x6 13x5 17x4. Transition - Rectangle To Round. Shop Grainger. I draw a vertical line from center I draw a circle on the surface of the rectangle at new center line. Tite Fit, Aluminum Straight Dryer Venting Duct With Transition Fitting, 2" x 6" Rectangular Duct, To Fit 4" Round Duct. The Mech-Q HVAC Ducting software module is an easy to use. D - Diameter (Round Duct) 4 - Transition type. I need to make a rectangular to round transition that I can give a specific length to, similar to the Rectangular Length Concentric Duct Transition from the part catalog. ASHRAE has assigned the square to round fitting the number SD 4-2. com is an authorized Nordfab Part stocking distributor offering a full line of products at exceptional prices. To calculate the rectangular duct area, we need height, width and length. If a round duct is required, a rectangular-to-round calculate total equivalent ductwork length using the. Broan 411 - 3-1/4" x 10" to 6" Round Duct Transition - Maximize the air and sound performance of your Broan ventilation fan or range hood using one of our wide vaiety of ducting accessories. Mech-Q Ducting is an add-on for AutoCAD, Bricscad and IntelliCAD. 075lb da /ft³). you how to calculate total equivalent ductwork length using. - Rectangular Transitions - Register Boxes - Return Air Cans - Riser Pipe - Riser Pipe - 45 Elbow 16" x 8" Square To 12" Round Transition Made From Galvanized Sheet Metal Custom Made per your meas. Hey guys, We are doing a little chute-work in the office at the moment, and have had the need to develop some bend/folded plate work. Hydraulic diameter: for a rectangular duct - diameter of a round duct whcih has the same pressure loss as the rectangual r duct at the same air flow rate and coefficient of friction. HVACQuick Custom Square to Round Duct Transitions. Always stagger take-off ducts by 12" to maintain pressure. A comprehensive duct layout indicating sizes, design airflows, pressure class, and routing of the duct system. Installation Instructions Over the Range Microwave Oven If a rectangular-to-round transition adaptor is used, the bottom corners of the damper will have to be : calculate total equivalent ductwork length using the approximate feet of equivalent length of some typical. A transition connects square or rectangular duct to a round pipe or round flexible duct. Their measurements showed that those two sizes of oval duct are equivalent to round duct at 5. The types of fittings to be used based on the designer's calculations of fitting losses (i. Round to 4" x 10" Rectangular Item Information. Friction Loss Calculator for Sheet Metal Ducts. This is approximately true for lower nominal R-values. I'd like to convert to a flatter rectangular duct (in the closet portion only) to save some room. Its object in ductwork is to transform a square or rectangle duct to a round pipe, or to connect a round pipe to a square or rectangular opening. 14 = 314 square cm (16 x 3. It's Okay to Ask "Wye" - When to use which Y and why. Get free shipping on qualified Transitions & Connectors or Buy Online Pick Up in Store today in the Heating, Venting & Cooling department. you how to calculate total equivalent ductwork length using. To develop the true length lines, construct the true length triangle XYZ with ZX equal to the vertical height of the transition in the elevation view. Installation Instructions Over the Range Microwave Oven If a rectangular-to-round transition adaptor is used, the bottom corners of the damper will have to be : calculate total equivalent ductwork length using the approximate feet of equivalent length of some typical. Standard are designed to complement rectangular, ten-sided, or round fibrous glass duct systems. For example, from Figure 1 , at a Reynolds number of 2000 (based on the hydraulic diameter), approximately 25% of the duct, measured along the center line. In air-delivery ductworks of HVAC systems, pressure losses across duct fittings such as dampers, sensors, bends, transition pieces, duct corners, branches, and even splitter attenuators are important in counteracting the pressure difference created by fans. Roof Cap 2/4Ft. If the duct is relatively small and the change is only in the height of the duct, such as a 12- x 12-inch duct changing to a 12- x 6-inch. All Rheem products meet or exceed rigorous industry and regulatory standards for quality, reliability, efficiency, and air & water quality. 05" on most metal duct calculator Round metal pipe =. If a round duct is required, a rectangular-to-round calculate total equivalent ductwork length using the. We do not carry all of these metals, but provide them as reference information. x (1) = 5 ft. Residential Hvac Duct Drawings by Geoffrey R. ASHRAE has assigned the square to round fitting the number SD 4-2. The 1 piece design offers easy installation. 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: q = kA(t1 - t2) L Btu hr (Eq. 4s x 10s rectangular duct. Also included: Duct transitions, tees & wyes, offsets, branches, dampers, diffusers, flexible duct, grills and other. A transition connects square or rectangular duct to a round pipe or round flexible duct. Vent extension piece, at least 3" (7. This stands for. Calculate the average velocity in the pipe and in the duct. Maximum duct length: For satisfactory air movement, the total duct length of 3 ¼" x 10" rectangular or 6" diameter round duct should not exceed 140 equivalent feet. 1677 [email protected] Alright, Im trying to make a section of ductwork that is a transition from 12x8 square to 8 dia round. Contact Us: (844) 289-0033 | After Hours Emergency Contact: (800) 217-4698. NOTE: If the existing duct is round, you must use a rectangular-to-round adapter, with a rectangular 3" extension duct installed between the damper assembly and the adapter to prevent the exhaust damper’s sticking. duct pieces. The bending is an easy process since you only need to make very small 15 deg. 6 cm) clearance must exist between the top of the microwave oven and the rectangular to round transition piece so that the damper can open freely and fully. transition piece developed in figure 12-53 is a scalene. The equivalent total feet is the sum of all elbows, transitions, wall caps, etc. Vertical Size *Max. Read Round Duct Diameter (inches) and Friction Loss Per 100' of duct (inches of water). I have explored some of the online calculators that determine rectangular duct dimensions for a given diameter, keeping in mind CFM and FPM. DUCT PIECES LENGTH x USED = LENGTH Rectangular-to-Round 5 Ft. Height: remember to add if bending the lower scrape in or out Upper Diameter: round use a slightly smaller diameter for less crimping or to finish. Flex duct =. I draw a vertical line from center I draw a circle on the surface of the rectangle at new center line. Then to get area in meter square, use the equation. Contact Us: (844) 289-0033 | After Hours Emergency Contact: (800) 217-4698. Transition - Rectangle to Round. A sheet metal transition is a custom fabricated duct to connect a new furnace or air hander to existing ductwork. Similar to the Taper pattern, it often has a double offset, in which case it is essential to understand which offset dimensions are being requested, and how to change them if necessary. Equivalent lengths of duct pieces are based on actual tests and reflect requirements for good venting performance with any vent hood. SPECIFICATIONS Provides a multi-gored bend between two ducts. Round Duct is the most efficient and economical means of conveying air. Rectangular to Round Transition for Roof Venting NOTE: The minimum 3" (7. Rectangular transitions, S offsets, Rectangular duct elbows, Square-to-round, Round tapers, Round tees, Round elbows Use this book as a handy reference or as a textbook to learn all the methods you may need. out of 5 stars 2. not coated duct. for eccentric round to rectangular fitting, use the custom fitting order sheet. 7m (Round(diameter 22 ) to rectangular (1. If a round duct is required, a rectangular-to-round transition adaptor must be used. Rectangular Duct & Fittings "L" Section Duct; Large Section Rectangle Ductwork; Turning Vanes Rectangle Section; Square To Round Transition; Rectangular Elbow; Large Elbow Takeoff; Roof Curbs & Curb Adapters; Commercial Duct Installation; Custom Duct Transition Plenum; Long Way Elbows; Welded Seam Flanged. Elbow (for wa D. 05" on most metal duct calculator Round metal pipe =. FPM Calculator. The following is a simple example of how duct pressure accumulates and is totaled in a section. I have several different instances where I need to creat a rectangular to round transition. Calculations are for 60°F dry air at sea level, from 5 to 3000 cfm (approximately standard air which is 0. Its object in ductwork is to transform a square or rectangle duct to a round pipe, or to connect a round pipe to a square or rectangular opening. It is constructed from all galvanized steel, and has rolled edges for safety. Nordfab rectangular to round transitions are ideal for transitioning round to rectangular ductwork or for use as a hood. add the equivalent lengths of all transitions and. Do not use this item for any installation or repair of potable water applications. They are easily routed in overhead space, between floor joists, or in an attic. If a round duct is required, a rectangular-to-round. Online Ductulator Free Duct Size Calculator. Transition_Rectangle_To_Round_2. The preliminary duct routing shown in the ductwork diagram, Figure 1, is used to calculate the longest duct run. The Eastern Sheet Metal Rectangle to Round Duct Calculator App is used by sheet metal. Mumma (1997) also applied a k-ε model to predict the pressure loss of a flat oval ductwork and compared Liu, W. The chart below shows. Available in malleable, zinc and steel, and with features like captive, deep-slot, tri-drive screws and more, Bridgeport products are the best choice for unparalleled field performance. Why? Round ducts take up more height than do rectangular or square ducts. A llows connections from rectangular grilles to round ducting. The Eastern Sheet Metal Rectangle to Round Duct Calculator App is used by sheet metal contractors and installers, HVAC engineers and contractors to quickly convert the following duct diameters: rectangular to round, oval to round, or rectangular to oval using the U. Ductwork - DIY heating and cooling product sales for the Do-It-Yourself home owner. Duct Size Calculator. 250] a = length of one side of rectangular duct (inch) b = length of adjacent side of rectangular duct (inch) De= circular equivalent of rectangular duct for equal friction and capacity (inch) Source: 2001 ASHRAE Fundamentals, p. For each new calculation a unique conversion scale will be generated for the range of volumetric flow rates and flow speeds for the length and width specified. For duct sizes not exceeding 24" high by 48" wide, Class2" wide by 11/ 2" deep hangers of 22 gauge sheet metal on 4 foot (max. not coated duct. While designing ductwork, it is important for engineers and ductwork manufacturers to geometrically construct the three-dimensional duct from a two-dimensional piece of sheet metal. Get free shipping on qualified Transitions & Connectors or Buy Online Pick Up in Store today in the Heating, Venting & Cooling department. Shop duct transitions & connectors and a variety of heating & cooling products online at Lowes. Duct Length The total length of the duct system, including straight duct, elbows, transitions, and wall or roof caps must not. The app is available for Apple and Android systems. We offer a complete line of rectangular to round transitions for spiral pipe. Pattern Making- Square to Round Transition SolidWorks Sheet Metal tutorial calculate hopper in Flat form. In this chapter we deal with nominal and balanced pressure loss calculation, and automatic dimensioning of duct systems Principles. Students will adjust the size of the ducts based on their calculations. A quick explanation on how to complete the triangulation on a rectangle to circle hopper and then find the needed true lengths to start the development of th. Top and base are parallel. Buy QF Transition Rectangular to Round* online. Height: remember to add for bending flanges in or out Top: wide x deep scrape: Bottom: wide x deep scrape: offset: at the: offset:. 178 Campbell St. The Square to Round pattern is a commonly used fitting with many variable dimensions and options. Enter Duct Airflow (CFM), Duct Velocity (FPM), Duct Length and the number of bends. Available in malleable, zinc and steel, and with features like captive, deep-slot, tri-drive screws and more, Bridgeport products are the best choice for unparalleled field performance. Open a sketch on the offset plane. • Specify Round End: Rolled Flanged Raw Hose Connection Part Number 189dd-0000-xyy00 x = material 1 - galvanized 2 - galvaneal 3 - black metal 4 - 304ss 5 - 316ss dd = diameter yy = gage 15 Style 189 — Rectangular to Round Transition See Hints for Ordering on page 27. Thanks for any help. Round Galvanized Steel Duct Transition-411 - The Home Depot. Create 2D & 3D rectangular, round and flat oval ducting. Various types of transitions are commonly used in the fabrication industry to: • Transform geometric shapes eg square/rectangle to round transitions • Convey materials eg hoppers and chutes • Transport air in ventilation systems eg duct fittings and fan casings. transition piece developed in figure 12-53 is a scalene. Can someone here please give me a little insights on making transition pieces? For example, from the heat exchanger opening to the supply duct plenum. They are easily routed in overhead space, between floor joists, or in an attic. DUCT PIECES LENGTH x USED = LENGTH Roof Cap 24 Ft. I have some equations which I cannot figure out. 6 lb 931141 RSC7X6 6" 6 7 lb 931660 Top Take-Offs • For transition from air plenums or rectangular duct to round pipe or insulated flexible duct. Beckfeld, M. 1-21: Round Duct, 2 Inch Lining (reproduced with permission from HVAC Systems Duct Design, SMACNA, Table 11. x (1) = 5 Ft. 9mm galvanised mild steel depending on size. transition adaptor must be used. ASHRAE has assigned the square to round fitting the number SD 4-2. -When the joints between the pipe and transition piece are not perpendicular to the pipe axis (fig. au Transition - Square To Round. Do not use a duct with a diameter less than 6”. Webinars HVAC Duct Construction Standards 102 - Rectangular Duct Tie Rods, New Tables (TDC/TDF), and Rectangular Duct Over 120' Event Objectives Gain solid understanding of how to construct duct in a resource efficient and sustainable manner that is compliant with SMACNA’s HVAC Duct Construction Standard. Rectangular to Round Concentric Transition Offset, Vertical Offset, Horizontal Offset, Double 19 20 Straight Duct with Round Tap RECTANGULAR DUCT ORDER SHEET. The table below can be used to compare equivalent diameters for rectangular and round circular ducts. "A procedure for predicting pressure loss coefficients of duct fittings using CFD (RP‐1493)” HVAC&R Research, 18(6), 1168–1181. Maximum duct length: For satisfactory air movement, the total duct length of 3¼" x 10" rectangular or 6" diameter round duct should not exceed 60 equivalent feet. Traverse Surveying is a popular method of surveying. * IMPORTANT: I f a rectangular-to-round transition adaptor is used, the bottom corners of the damper will have to be cut to fit, using the tin snips, in order to. Weight-based labor formulas generally allow 50% more pounds per man-hour for installing round and flat oval spiral duct versus rectangular. Custom Duct Fabrication Capabilities. break point varies by manufacturer). Duct Direct 8610 Wallisville Rd. And it shows the velocity and/or static pressure loss of air for both types of duct shape. the round duct than the rectangular one. Duct Calculator App for iPhone and iPad. The Mech-Q HVAC Ducting software module is an easy to use. x (1) = 5 Ft. 75" to 12" dia. If "ASHRAE 2013" is selected, Flexible roughness is 0. Residential Hvac Duct Drawings by Geoffrey R. Formula: d h = 2 × a × b/a + b. Use insulated duct or duct board in unheated spaces. out of 5 stars 2. I try to calculate the pressure drop on duct transition lenght around 0. We do not carry all of these metals, but provide them as reference information. When calculating your duct. Transition - Rectangle to Round. In this article, the following conventions and definitions are to be understood: The Reynolds number Re is taken to be Re = V D / ν, where V is the mean velocity of fluid flow, D is the pipe diameter, and where ν is the kinematic viscosity μ / ρ, with μ the fluid's Dynamic viscosity, and ρ the fluid's density. These rectangular ducts are used as the main trunk line run for your home's ducting system. First, come down the left-hand column until you reach 17 inches; then trace the line horizontally across the columns until you reach the column headed by 16 inches. 2, Duct Design, and the Air Distribution Institute. Round or oval ducts have advantages over rectangular ducts and this calculator app makes transitions easier. If a round duct is required, a rectangular-to-round transition adaptor must be used. Size of Duct depends on various factors like : 1) Cfm of duct 2) Required static pressure in duct 3) Shape of duct piece like bent, offcet, length, round etc Speed-Sheets ACCA Speed-Sheets are Excel spreadsheets you can use in conjunction with certain ACCA technical manuals to assist in learning these important system design concepts. Looking for BROAN Transition Duct, 3 1/4 x 10 to 6" Round Duct Size (In. Flexible duct can be installed in place of galvanized pipe in many applications if allowed by your local HVAC codes. The kits contain sheet metal pieces and an instructional DVD video to show you how to make sheet metal transitions. Round duct diameters are typically limited to multiples of 1 in. This stands for. there are several reasons for specifying round ductwork. · Calculate air velocity as a function of air flow and cross section; · Calculate local C-coefficients for each fitting used; and · Calculate pressure loss using the friction chart. Friction Loss Calculator for Flexible Ducts.