Flex duct main trunk Sadly, this was not the work of a DIYer but an HVAC “professional. The warmer rooms are at the end of the trunk line. Flex duct consists of a plastic inner liner attached to a metal coil that comes already covered with a layer of fiberglass blanket insulation, which is covered by foil or plastic Collars that are specifically made for flexible duct have a raised bead to I'd want my flex ducts to be able to handle more than 1,200 cfm - somewhere around 1,350 cfm to keep the change of backpressure on the system low. I have a . If we use flex duct and don’t pull it tight, the pressure drop will be greater than if it were pulled tight. How did they describe the work they were going to do? Did they actually put dampers on and balance the system? With the 12" supply installed we take two 7" runs (-300 CFM) and two 6" runs (-200 CFM) off the remaining trunk for a final total of -125 CFM - 125 CFM. Bruce Wrenn. As one poster stated, there are calculations done based on how many CFM will be moved through the next duct. Flex Duct: This easy-to-install and inexpensive type of duct contains three layers: an inner layer that uses a spiral wire rib to hold its shape, a fiberglass center layer that provides thermal protection, and an outer layer that acts as a vapor barrier. Flexible duct work must be stretched tightly for maximum air flow. Length of the duct and supplies will be a factor as well as the number of supplies. With 2 boot registers, that would put me at approx 100 cfm/boot and (according to flex duct calculator with . Two L sections snap together to form the rectangular duct. For double-unit mobile homes, you’d need 110-120 ft of flex duct, costing $4400 to $5000. Adding heat runs in a basement may change the airflow in the ductwork going to other rooms. But you are more likely to get a hack job. That is if the trunk line is repairable, not squashed and torn or flattened, and is simply leaking air at the seams For example, I have a flex duct running from the main trunk that does a 180 degree turn around a roof truss simply because the register box opening faces 'away' from the trunk. B/c of the way piping, joists and otehr things are, I can't easily access the top of the As a general good practice, you should fix the height of the main duct to be about the same as the height of the HVAC unit. It would make a lot of sense for this third system to be run with flex, because it is in unconditioned space, so it 16" flex duct. Two pieces must be ordered to produce a full section of duct. Using these numbers you can calculate the appropriate HVAC duct size. Size is 20"x24"x5 or 6" filter. I am tempted to do it myself as I'm pretty handy, If you So there is probably another 8-10" of unusable trunk line. For instance, if your HVAC unit has a height of 250mm (10″), your main duct should also be 250mm (10″). The Environmental Protection Agency (EPA) states in its Energy Star® Right-Sized/Compact Ducts, “The major goal in duct design is to provide proper air distribution throughout a residence. George2. It feels like a "good fit" that won't pull out, my main concern is. When my home was built in 2016 the HVAC runs from the furnace in the basement up through the house uses 7" R4. Then from the box run to a 7” flex duct to the 4 Seal it with mastic. 53 ton) R-4. What kind of fittings am I supposed to use to tee off a flexible duct trunk line to the ductwork that serves my rooms? I've tried searching for it, and I can only find fittings for a metal trunk line tee'ing off into flex duct. They sell vent caps that you can push fit into the truck and then just The materials utilized in manufacturing IMDUCT R8 Flex Ducts consist of aluminum on the exterior, glass wool, aluminum ducting and stainless steel spiral wire within. The duct trunk refers to the large main trunk, while the duct pipes are what connect the trunk to all the rooms in your house. The only new homes using rigid are the high end homes and even a lot of those are using flex. losses. Could we cut off the end and just attach the flex? Plenum or Main Trunk, Trunk Duct, Takeoff, and. Installing flex ducts is like solving a puzzle. . Each register should have its own damper that can be accessed for adjustment in order to air balance. main. 2 insulated flex duct. Otherwise you should expect issues with your system typically in winter time. Commented Jan 10, 2022 at 21:33. Won't get much air through a duct board trunk that is ran in between the joist. I use a hybrid design as mentioned above. The flexible duct branch line will be connected to the rigid duct board trunk with a flex duct start collar (also called a “take-off”). I’m not saying that’s a good thing. In order to maintain velocity, reduce duct size. Have someone who is reputable look at it. This aluminium is commonly known as the flex pipe in the HVAC trunk line. This 20ft straight run would be perfect for a large flexible duct, and ductwork wyes are available to create the smaller branches. If you have any other inquiries about our Master Flow products please email warrantyllbp@gaf. 4. A 6" pipe will deliver about 120 cfm at . Ducting, Air Circulation and Ventilation Systems - Installing flex insulated duct into main trunk lines - I am going to be installing a solar thermal panel which will tie into the main trunk lines of the house. They sorta wrap around each other and one is bent slightly against the other. It has an Aprilaire box filter (2200 series) in the attic, just prior to the furnace. bmp file. If you really can't fit anything in there, from your picture it looks like you have access to the opposite side, so you can get a 5" holesaw and a 18-24" hole saw extension bit and drill through both sides of the duct. So it may be a wash. The supports need to be at the manufacturer’s I have to run a flex duct from opposite side of main trunk, as other side of the trunk in the direction flex duct is running is not accessible. Last summer I took on a project of insulating an attic with DIY closed cell spray foam insulation kits. This is the key to proper air delivery to each room. The start collar and take-off hole in the duct board trunk: The length of flex works surprisingly well for sound. I probably need more return vents. So I'm hoping we can get away with a rigid duct for a trunk (running parallel to floor trusses) and then 6 inch flex duct going out to the exhaust and supply registers (through the In this tutorial I am happy to show you how to properly install flexible duct to a register can for all you heating & air conditioning ventilation do it your In this HVAC Training Video, I Show and Explain Trunk Duct Fittings, Elbows, Dimensions, and Names so that an Apprentice or Helper can Learn the Terminology So, at the trunk you would cut in a 6" saddle (this is a "tap" that your new duct will connect to) and at the other access you would cut a "4x10x6 90 boot" into the floor. However, for areas like walls, one necessitates flexible options like aluminium. Basement and main floor are served by the basement trunk. Back. I did find out that the flex duck to them is the old gray R4 flex line, so I'm putting R8 flex on them and see if that helps. My question is: how do I install the insulated duct, from the panel, Rectangular trunk duct is used as the main trunk lines in HVAC supply systems. But a flex duct of the same size allows about 300 CFM through it. I do agree with what Ponytl said about possibly avoiding some duct loss with flex. Also, the 26X10 trunk you would be connecting to would need to be made bigger, so as not to rob air from the first floor. Stumpy, the flex duct amputee, is the relic of a poor duct retrofit. You reduce supply duct once you've used a take off to reduce the air flow. For example, a round 10-inch metal duct lets about 325 CFM through it. 0/0. Airflow has a hard time making turns at high rates of speed, With this in mind, let’s think of the supply plenum or main trunk of a duct system as a fast-moving interstate with branch duct takeoffs serving as off-ramps. B/c of the way piping, joists and otehr things are, I can't easily access the top of the POL_DOP K-FLEX ST DUCT AL CLAD - 3-25mm thk sheet 01101908201 POL_DOP K-FLEX ST DUCT AL CLAD - 26-50mm thk sheet 01041908201 POL_DOP K-FLEX ST DUCT ALU - 6-25mm thk sheet 01032008201 POL_DOP K-FLEX ST DUCT ALU - 26-50mm thk sheet 01042008201 Foil-Covered or Mylar® Covered Fiberglass Flex Duct. This construction is well-suited for use in medium to moderate high-pressure HVAC systems due to its lightweight and adjustable length flexibility. I am in the process of finishing my basement and I would like to tap into the existing runs. As part of this project, the HVAC ductwork located in the attic was also encapsulated in closed cell spray foam (HVAC contractor put thin Reflectix on the main trunk of the duct system and they used R-6 flex to the register boots their work was extremely Hey guys, I'm still working on setting up my shop and I've come to the point where I'm pretty sure where my tools will go for now. Apply a sealant to the inside of the rigid duct. But really, it all comes down to your installation. We opened our P&S Division with a goal of participating more in the total ductwork job and not just the main Typically, the duct design will consist of one or more main supply trunk(s) and perpendicular duct branches serving each of the ceiling registers. Two of the systems are spec'd with flex duct, one is not. He crawled back across the attic and very nicely told me that people don’t typically [] For example, a round 10-inch metal duct lets about 325 CFM through it. I would like to put an elbow instead of the straight collar that the flex is tied to to extend the lines so Typically, the duct design will consist of one or more main supply trunk(s) and perpendicular duct branches serving each of the ceiling registers. My current ductwork consists of a main trunk for supply that is rigid, with flex off of it (ranging from 4 to 6") to the supply registers. Duct board products are available with coated or faced airstream surfaces. It is crimped on both ends for an easy fit. I noticed he attached these flex ducts by just cutting a tight fitting hole in the trunkline and pushing the Hey guys, The flex that is connected is slightly bent. For example, I Next step will be the round pipe or Flex Duct coming off of these HETOs and into the Air Distribution package. • At the end of the duct system, choose a minimum friction rate (typically 0. To properly size your ducts, you need to consider The better duct system IMO is a main trunk with drops. So if you had 1200 cfm then branches off, the remaining air flow volume is used to size the next section of the main trunk. 5 ton system. 1 static pressure. Always connect the branch duct to a trunk duct for the best air flow. As a general good practice, you should fix the height of the main duct to be about the same as the height of the HVAC unit. Insulated Flexible Duct R6 Silver Jacket. They are known for being very adaptable and easy to install. It’s cheap. However, flexible aluminum, often called Can someone tell me whether there are any significant disadvantages for using flex duct for supplies (off the main trunk) rather than rigid metal ducting? Thanks! Reply . For instance, the main trunk is larger than the smaller runs that go from the trunk to the vents. They sell vent caps that you can push fit into the truck and then just In my second year in HVAC, I went out with a senior technician to install a supply duct for a bathroom in a house. Designed to wrap around and insulate exterior of commercial and residential ducts and plenums. Flex duct consists of a wire coil covered with pliable plastic, insulation, and an outer layer of vinyl or Find 14-Inch flexible duct at Lowe's today. When I had to replace the duct work at my cabin (it was ALL insulated flex, even the main trunk line), we went with metal for nearly all, but insulated flex for the last 10' or so of For supply and return ducts, short branch duct runs, off a centrally-located trunk duct(s) is the practice recommended by HVAC industry standards. For example, for a 210 sqft room I would need around 195 cfm. If I can convince my former-builder hubby, I will be using metal ducts for the main trunks and then flex duct to the vents. I want to use fiber board for the main trunk line (the run is 24 feet long fom the air handler to the last drop). Personally, I would use a metal main truck and flex drops. How the process works: Install dampers at the registers to adjust airflow. Southwark SD20X10X60. Lots of the runs are 10 to 15 and sometimes 20 feet long. I have a 2 ton system with 8 10"-12" flex supply lines off the trunk dropping down to 6" duct for the last few feet to the registers and the air velocity is pretty healthy (a little too healthy!) at 800CFM. This page continues our discussion of ductwork transitions. For my setup I ended up using insulated flex duct section on the return lines ( main trunk is steel). I wouldn’t accept it if the plenum is flex, it is definitely not as good as a hard The official recommendation from the ADC is that flex ducts should sag no more than 1/2″ per foot of length between supports. It is that simple. Did you know that many HVAC contractors don't install flex duct properly? Here's how they should do it, if they even use flex duct at all. The section of supply I’m currently trying to address is all flex duct with two “hubs” (dunno the official word) from which there are runs to registers. Metal Hanging Strap - used when hanging metal duct, commonly called plumbers I have to run a flex duct from opposite side of main trunk, as other side of the trunk in the direction flex duct is running is not accessible. I’m not opposed to flex duct. You can buy foil-faced duct insulation (foil side out) or just cut some insulation off the unused flex duct to cover the patch. It is light weight, easily modified to fit into areas with space limitations, and can be sealed and insulated which offers a moisture barrier as well as an acoustical barrier for maximum efficiency and comfort. It’s ubiquitous now in homes with forced air heating and cooling systems. Ducting, Air Circulation and Ventilation Systems - Adding new duct off main trunk - I am added a room to my basement, happens to be right beside the furnace and air handler (in fact closet doors in room will open to get to it). Constructed of 28 Gauge galvanized steel. All ducts and fittings metal except for flex, last couple feet, and attched to wall registers. Let’s get serious. Flex Duct & Ductboard . It is composed of a spiral wire frame encased in a durable, I got all the right sizes for the rooms (using flex duct). The duct trunk, typically the largest, serves as the main artery, while duct pipes branch off, extending to individual rooms. US Duct offers single, double, T, and Y branches, which are also known as Lateral, 'Pant', T on taper and/or Y-branches. Add to compare list. It goes pretty close to that existing 4" rigid duct to the bathroom that is not connected to anything. and I'd like some opinions on running 6" vs. MORE DUCTWORK TRANSITIONS Rectangular Side Take-offs and Vertical Ells. com or call Technical Services at 800-211-9612, Mon- Fri, 8 am 5 pm EST. Can someone It has two 14" flex ducts as well as a 10" flex duct going into it. See Flex Duct. Rectangular trunk duct is used as the main trunk lines in HVAC supply systems. 5-meter intervals and the vertical at no more than Building Science Geeks love to hate on flex duct in HVAC systems. They can fit into small spaces where rigid ducts cannot. Probably about 10X30. So, what's the difference between flexible ducts and conventional metal ones? Here's a quick breakdown: Metal ductwork consists of thin sheets of galvanized steel that create rigid round or square-shape tubes Someday, I might cut a hole in the ceiling of a closet along the way, remove the old duct "arthroscopically" (reach up through a 2x2 foot hole, cut out a 1-foot section, pull it down, pull the rest of the duct forward, repeat until the whole duct has been removed in 1-foot chunks), and replace it with flex duct but that's a future project, not a project for next week. When posting in certain forums, Skip to main content. We're planning to install a Renewaire EV90P ERV with dedicated ductwork in our new 1900 sq ft home. Your home's ductwork typically consists of three parts: trunk lines, return ducts, and ducts that connect to the trunk lines. Time being money is the driver behind flex over rigid. Used in temperatures between 40 deg F For example, I have a flex duct running from the main trunk that does a 180 degree turn around a roof truss simply because the register box opening faces 'away' from the trunk. When installing a flex duct, a technician slides the inner liner over a sheet metal collar. They take pictures of terrible flex duct installations in crummy attics and link to this T Rectangular trunk duct is used as the main trunk lines in HVAC supply systems. Differences: The main difference between the two types of ductwork is that Good ductwork design and layout, whether it’s ‘trunk and branch’ or ‘home run’, includes an understanding of balanced air pressure, the roles that friction and turbulence play First cut a bigger hole from opposite/bottom side to make the required hole to the top from inside. What's better when running residential flex duct? Longer runs from the plenum to each register with dampers, A trunk duct with appropriately sized runs ro vents. Never locate ducts at the end of the trunk line run. Use insulated duct or duct board in unheated spaces. Skip to main content. For the flex duct, the average installation and purchase cost for each foot of duct is $40-55. Too much flex builds static pressure, especially long runs. You install a starting collar and connect your flex duct to that. My question is how best to open the trunk and extend it. So my house was built in 94 and uses all flex duct except for the main trunk. BACK; Southwark TD Series Trunk Duct, Rectangle, 25 x 10 Inch, 60 Inch L, 26 ga T, Galvanized. 5-Inch and 2-Inch duct board and zips tight or attach to sheet metal trunk lines with screws through the pre-drilled holes on the collar flange. Ready To Ship! 109 In Stock Now! Check Availability. I've done the rough math on how long the runs will be, bends, CFM requirements for the machines, etc. 16 inch flex duct. Link to Lowe's Home Improvement Home Page. Contractor 1 wants $2200 to replace all the duct I had a quick play and for the life of me I cannot get the spigot to default to the top - sides and underside no worries. So on to my question. It is ideal to leave between ~100 CFM and ~250 CFM in a duct system as hanging strap for flex duct. However, many factors influence the system’s efficiency, including duct sizing. Insulated Flexible Duct R6 Silver Jacket is used in standard Heating and Air Conditioning (HVAC) systems and some venting applications. The photograph just below shows foil-faced smaller-diameter high-velocity HVAC ducts as well as the main trunk line which has also been covered with foil-faced fiberglass insulation. I won't bore anyone with the details of why I cannot get in contact with the person that did the load calc and duct design for my project but here's what I need advice on: There are 3 systems for the house. Flex duct is done wrong 99. 2,12 Insulated Flex Duct,12 Inch Insulated Flexible Duct HVAC, Ac Flex Duct 12 Inch Insulated, for Heating and Air Furthermore, minor duct compression is acceptable. • Use insulated duct or duct board in unheated spaces. The Master Flow 20 in. This will help to create a watertight seal. In most cases, these pipes and trunks are made from galvanized steel, but flexible aluminum may Flex duct allows easy connection from the main duct trunk to the HVAC grille. jpg or . Seal all connections with duct But in this case, being there is only 1 other duct off the plenum, and this 180° flex being the main supply trunk. Texas A&M did a study on the effect of flex duct not pulled tight and the results are astounding. Make sure that the seal is tight and that there are no gaps. You can even get fancy sound absorbing flex that has acoustic data. The length of flex works surprisingly well for sound. The duct insulation R-values I mentioned above are what’s on the product label. Plenums, main trunk line, and runs greater than 5 feet are all metal. I’m thinking of switching to rigid round duct with takeoffs located close to the respective registers. For example, I have my ERV connections for each bedroom with about 10' of 4" flex with 2 90deg bends to a main trunk. I was told this by a contractor: 3 ton heat pumps with the new r410a refrigerant recommended size is 18" on the return duct. If you don’t know anyone, ask people you know who may know someone. All of the returns are flex. Learn about HD Flex™ FLEX-PLATE1U Fiber Optic Enclosure Accessories and other Fiber Optic Panels, Main Menu. Anyway I'll try to do a better job of explaining the layout. • Always stagger take-off ducts by 12" to maintain pressure. These products permit rigorous cleaning of the duct surface where dust has been allowed to collect in the duct due to lack of filtration or poor maintenance. Lastly, make sure that you have all take offs (individual runs off of the main trunk line) have dampers, This flex connector with a 6" body is used to connect two sections of insulated flex duct. The two biggest factors limiting trunk duct size in a residential setting are cost and space. Note that if your new unit evaporator coil (indoor coil) is freezing (everything else being correct) than you fan is either not working, you have a blockage in the duct or just not getting enough air a crossed the coil due to increased duct etc. The duct size varies from six to 10 inches, depending on how much air needs to be moved. round snaplock pipe or Flex Duct). (This type of system is sometimes referred to as the Navigating Tight Corners with Flex Ducts. The return has a big return plenum with a 16 round flex duct attached. Tape or mastic the edges of the foil to the trunk to keep moist air out of the fiberglass where it touches the cold sheet metal. 2 feet is my general rule for takeoffs. ” Image Credit: Energy Vanguard Poorly supported flex duct. Like The flexible duct branch line will be connected to the rigid duct board trunk with a flex duct start collar (also called a “take-off”). Open menu Open navigation Go to Reddit Home. us. Sold in "L" sections. Using ducts that are too large or too small can render your HVAC system pretty useless, so it’s important to know duct sizing rules of thumb. Ducts sized for 450 FPM air velocity are more "efficient" than ducts sized for 900 FPM air velocity. The distribution is pretty good too. View Profile View Forum Posts View Forum Threads Professional Member* Join Date Dec He ran a metal trunkline down my basement with a bunch of 6" insulated flex lines going off of it to floor registers. Well, that’s the idea anyway. I have a 2hp Grizzly DC 'rated' at 1550 CFM, which I plan to use on only one machine In a house, I have an empty cavity above a hallway ceiling and below the main ceiling joists (the bottoms of roof trusses). In a single trunk line, when should I reduce the size of the trunk to maintain velocity? I seem to remember in an NCI class awhile Is the trunk really flex duct and not just a round sheet metal duct? I don’t even know how you do that with flex. Upstairs has a chase to (sorry, the builder made me do it) the attic and the upstairs has insulated flex duct to the ceiling registers. I've lived in the old flex duct in the attic country my whole life and don't see a problem with it, although many hate flex duct. At the 23x8 duct is where the trunk is tee'd. We opened our P&S Division with a goal of participating more in the total ductwork job and not just the main Trunk Duct. Master Flow's sturdy Rectangular Duct is used as the main trunk lines in HVAC supply systems. Replacement: $9. Would capping it off at the end be a safer bet instead of terminating at the trunk? – basement_diy. So you’re missing out on about 8% of potential airflow. Flex duct Let’s get serious. 14. R-6 duct insulation: 6,305 BTU/hour (0. If this is the case, consider contacting an HVAC professional to inspect your duct system and make a recommendation regarding insulation or complete duct replacement. The door option may or may not work depending on where the return is in the main part of the house and its ability to actually draw the air from that room. Manual D is what you would use to determine what friction rate to use to size the trunk and supply lines. 33. Sorry — there are fixes, but they are ignored. You need to: Navigate tight corners. Flex duct consists of a wire coil covered with pliable plastic, insulation, and an outer layer of vinyl or foil. I have two at each ends of the I had similar concerns about plastic ducts, ventilation and noise. Drive and "S" Cleats are sold separately. ) We don’t design for compression, but you can see that if the installer used flex and didn’t pull the inner liiner One is, the main trunk is sized the same for the complete length of the run. Well suited for main trunk lines, supply and return lines, connecting lines, plus runs to diffusers, room registers, VIVOSUN 6 Inch 25 Feet Flex Air Aluminum Duct for Ventilation, 2 Clamps Included, Long Heavy-Duty Multi-Layer Dryer Hose Vent Kit, Duct Fan Systems. I think I just have add a tee and then attach boot. For straight duct sections, the effective length is the same as the length. A Main Trunk Line 11 What it Does? STAGE 2 The main trunk line is the central distribution source for conditioned air leaving the plenum. You need to check for a place for return air as you mentioned. High Energy Bills. So He ran a metal trunkline down my basement with a bunch of 6" insulated flex lines going off of it to floor registers. The 8"X14" duct could handle all the airflow required for the basement heating. It’s attached to a return trunk line 14x8, that has a 16x16 grill on the 1st floor. For example, a one-to AC system typically uses 10-inch ducts, while a 4-ton AC system requires 18-inch ducts. By Deflecto Product Expert | May 3, 2023. Chicago-specific SpacePak/Unico Flex Duct Question . 10” to 0. According to my calculations, the correct interior size should be 10x18 (180 in2. Find durable solutions to optimize airflow and distribute conditioned air effectively. Flex duct allows easy connection from the main duct trunk to the HVAC grille. The stiffer solid core cable is great for cleaning main trunk lines because it gives you better control of the brush head. I wanted to verify with you guys since the cost of upsizing the ductwork is high in this quote, whether it Trunk ducts also have endcaps on each end. Booming sounds may signal a lack of sufficient The DSC6 is used to connect flex duct to the main HVAC trunk line. Back {{ i18nSubstitutions The HD Flex™ Enclosure Trunk Slack Plate is design for excess to hold trunk slack and fits in a 1 RU footprint. The temps on a warm day are usually 5 degrees warmer at the supply ducts at the end of the trunk line. These calcs are from manual D. assuming the bullet above is correct, I Trunk lines are almost always rigid rectangular duct of 10x12" or larger. Green Building Advisor. The opening from the main furnace is 26x19" and then goes to a transition duct down to 23x8. Using an arbitrary friction rate is asking for a bad duct design, and air flow problems. It’s all saggy with peaks and valleys and half hazard. Support the horizontal flexible air duct at 1. 3”/100;’) and velocity limits (next slide). Flex duct. The Insert a collar or duct connector into the hole, securing it tightly with duct tape. Flexible Blanket . How often do you think you get the full labeled R-value? All US Duct branches are 18 gauge or heavier, which enables us to weld the branching part to the trunk to ensure a very tight seal. Typical two-story home in my area, with a basement. Many times, these ducts and pipes are built out of galvanized steel. Usually in this design the air handler centrally located in the Liberal sizing for the FURNACE trunk duct at 1400 CFM would result in an 18" dia duct. The photo below shows the way the return duct is routed, bent around a roof truss. See Ducts. I had an addition put on my house and I need to splice into an existing duct, run across ceiling and into another room. Then you take a box of 6" "flex duct", and push it from one This includes a new main trunk line, which is now 18" flex duct. The easiest and best is to run square or round metal duct and use takeoffs for each branch. It is the "One Collar that Fits All". From my A/C supply plenum, I will have a trunk (approx 20ft straight run) with 3 branches coming off (each about 2 ft runs). 06-24-2014, 07:25 PM #2. View Profile Here at Conditioned Air Solutions, we only use flex duct and sheet metal—no duct board. I have a space in finish basement where I have to supply heat from ceiling. In Northeast Florida I run into rigid in all of the 50's houses that I remodel, but just about anything built after the 60's is going to be flex. Usually in this design the air handler centrally located in the I just got the rough-in completed on my HVAC system and was surprised to see a “fabric” flex duct used to connect the main trunk lines in the basement to the vertical supply stacks going upstairs but not on the return air coming back down. Think of a trunk duct as the trunk of a tree and the branch ducts as the Cut the flex duct to the desired length. But in ceiling, in some places, main supply trunk is not reachable or some occupied by other vent for upstairs. I agree with what duct design expert Jack Rise said on the podcast when I asked him about flex ducts: “There's a lot of problems with flex duct, there really is, and it's a good product, [] It is the fastest way to connect duct to trunk lines or to the main HVAC unit. There are many different HVAC flex duct sizes to choose from, according to your needs. The other is similar, but the length can be run out, to up to 50 feet. ITA_DOP K-FLEX ST DUCT AL CLAD - 3-25mm thk sheet 01101908201 ITA_DOP K-FLEX ST DUCT AL CLAD - 26-50mm thk sheet 01041908201 ITA_DOP K-FLEX ST DUCT ALU - 6-25mm thk sheet 01032008201 ITA_DOP K-FLEX ST DUCT ALU - 26-50mm thk sheet 01042008201 Adding extra 16"x8" will not effect the airflow anymore than the extra lengths of 6" that would be required if the main duct was not extended. Next step will be the round pipe or Flex Duct coming off of these HETOs and into the Air Distribution package. I would prefer this duct to be cylindrical (not bent). Related Products. Blogs. • Flexible duct work must Flex duct is often used for run outs, with metal collars used to connect the flexible duct to supply plenums, trunks, Figure below illustrates that the main trunk duct becomes smaller after each takeoff, ultimately reducing to a single branch duct at the last takeoff. An outline is traced in the rigid trunk duct and cut out with a utility knife. This product was proudly made in the USA using POL_DOP K-FLEX ST DUCT AL CLAD - 3-25mm thk sheet 01101908201 POL_DOP K-FLEX ST DUCT AL CLAD - 26-50mm thk sheet 01041908201 POL_DOP K-FLEX ST DUCT ALU - 6 Here at Conditioned Air Solutions, we only use flex duct and sheet metal—no duct board. 4" duct. This is limited to 24-foot runs. In most cases, these pipes and trunks are made from galvanized steel, but flexible aluminum may be used in situations where walls require a more bendable alternative. Using the calculation above for the rooms in my house, I believe the existing flex ducts are grossly undersized. The aluminum jacket on the new stuff isn't prone to rotting like the old grey jacket flex from yesteryear. This is a 2. Because it’s a bendable This is without a main supply trunk. Indoor Air Quality . 20X10 and 12X8 supply trunk ducts have nasty fiberglass lining I need to It is the fastest way to connect duct to trunk lines or to the main HVAC unit. but possibly having duct loss due to flex. Or pay an HVAC guy a small fee to take care of it for you. If the trunk is perpendicular to the truss bottom chords, Flex duct runs should be pulled taut to reduce internal airflow friction. Moving the furnace allowed them not to redo the main trunk line and balanced out the airflow. It's going to be a budgetary strain to install hard pipe for all the entire system. • Never locate ducts at the end of the trunk line run. A properly designed system will have the least friction (restriction). If your builder didn't properly facilitate new connections for your basement, you may Flex duct is a type of ductwork that is flexible, making it ideal for connecting supply air outlets to the main HVAC trunk line, especially in tight or awkward spaces. The Environmental Protection Agency (EPA) states in its Energy Star® Right The smaller the duct the higher the velocity/loss of pressure if the volume is constant. Duro Dyne Flex Duct Strap 36 inches at 2J Supply, Helping Contractors Install Comfort Since 1962. Unless you made it 10" deep. 66 ton) The numbers are even higher for the additional heating load. 81 to $30. It just depends on the lay-out. If those dampers can’t be accessed from below, you’ll want to install them close enough to the register so that you can Air duct cleaning is a process of removing dust, debris and other contaminants from the ductwork system. Can I just split the 8" rigid into two 6" flex? Trunk ducts, connect to the main HVAC unit with start collars and are made of larger diameter sheet metal, to transport high volumes of air from the main HVAC unit to the branches of the duct system. So there is probably another 8-10" of unusable trunk line. 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. Customer Reviews. Also long-lasting, more durable than flex-duct, lightweight. Greetings! Flex should only be used in short 4 to 6 ft takeoffs from a main rigid trunk to registers for supply. Sometimes flexible ductwork is used for branches running off a flexible or sheet metal main trunk. All US Duct branches are 18 gauge or heavier, which enables us to weld the branching part to the trunk to ensure a very tight seal. 20 in. You can run an entire trunk duct in one size with no reductions and still deliver the required volume of air at each register with balancing dampers. It would make a lot of sense for this third system to be run with flex, because it is in unconditioned space, so it I currently have a 3 ton with 16 inch metal return duct work. This is in basement, I am using start collar with damper and then attaching 90 degree elbow. The flexible cable lets you clean ductwork with turns and drops. If the trunk is perpendicular to the truss bottom chords, Flex duct runs should be pulled As discussed in our Hvac for Beginners main page, each component of a forced air system, from the filter to each branch duct, adds a certain amount of restriction to the airflow of that system. I'm trying to finish an en-suite bed/bath that currently has a capped 8" rigid duct coming off the main trunk. As long as you take two runs out and In this video we show you the correct way to connect flexible duct to a round collar to ensure no air leaks into the attic. Of course, all of these will be insulated. Your e-mail address will be shown in the forwarded message. 5. ALL PRODUCTS. 6% of the time. If you cannot get people to do it right, you should get rid of it. For your living room i would take your main 18” duct if close to the main supply and tape off of it with 14” or 12” duct that runs into a spider box (see pic) located in the center of the room. In this HVAC Training Video, I Show and Explain Trunk Duct Fittings, Elbows, Dimensions, and Names so that an Apprentice or Helper can Learn the Terminology A good HVAC duct sizing rule of thumb is to measure rooms in your home, the necessary airflow rates, and friction loss rate. It is light weight, easily modified to fit into areas with space limitations, and can be sealed and insulated which Flex duct in short amounts (4 feet or less) is perfectly fine for quality and performance. I’ve been thinking I’m not getting the kind of efficiency I could be getting. For now you may want to simply concentrate on the existing metal trunk line, sealing it all up with aluminum tape and/or mastik (all the collars which are connected to the trunk line as well) and then only run new flex ducts. BACK; Adhesives ; Collars and Takeoffs ; Duct Boards, Wraps & Liners ; Duct Ties ; Flexible Ducts ; Sleeves . A flex duct is Rectangular trunk duct is used as the main trunk lines in HVAC supply systems. Study with Quizlet and memorize flashcards containing terms like Which class of manufactured duct has the lowest flame spread and smoke developed ratings?, A manufactured air duct that meets all 15 UL 181 tests is classified as?, Organizations that set safety standards for manufactured ductwork include? and more. x 25 ft. Tape or mastic the edges of the foil to the trunk to Explore our selection of trunk ducts for efficient HVAC systems at 2J Supply HVAC Distributors. There is flex duct out there with a higher R rating that is insulated quite well compared to the old stuff. Based on how much you need, it can vary, depending on how many collars, straps, etc. Lowe's Credit Center Order Status Weekly Ad Lowe's PRO. Last take-off run to be located 12″ – 18″ from end. [] Skip to content. Commonly, these trunks and pipes are crafted from galvanized steel. Single-unit ducting takes about 60 feet of flex duct, costing $2100 to $3100. The R8 designation highlights the duct’s round shape and ability to Ducting, Air Circulation and Ventilation Systems - Adding new duct off main trunk - I am added a room to my basement, happens to be right beside the furnace and air handler (in fact closet doors in room will open to get to it). The reason is the main trunk allows the system to 'pressurize' properly and accomplish even velocity at each vent. What is the proper method to supply air to both the bedroom and bathroom? The bedroom is about 135 sq-ft and the bathroom is about 35 sq-ft. So now that we all understand duct design a bit better, time for a bit of reality. Like regular HVAC duct, flex duct work needs to be sized appropriately in order to flow the air volume, which is measured in cubic feet per minute (CFM), correctly. Design looks good. The installer can show up and rough in a whole duct system without ever having seen the house before and without having a duct design. ) 1. Flexible duct, known as flex duct, is very convenient ducting for attaching supply air outlets to rigid trunk ductwork, and, in many cases, flex duct comprises the entire duct system. Flex ducts are made of plastic. 06 to $37. Musings If you have a 28’ run of 8” duct that is an extension of the main trunk AND you end that run with a boot (register), then what you have is not a We still run main trunk, and labs and only use flex duct to connect a diffuser to a rigid duct, rarely more than 10ft away. Here at Conditioned Air Solutions, we only use flex duct and sheet metal—no duct board. The duct trunk is the large main trunk, while the duct pipes connect the trunk to various rooms. Helpful. There are two problems: #1. install a collar and duct to the top. This main trunk duct line disperses air along the way into Branch Duct that will then take the air into specific areas or rooms of the building. Am I being anal about this? There are two ducts that tie into the main supply trunk line. Does it have to be made of the same square shaped aluminum Seal it with mastic. Now I am ending up with reuse the existing branch of 7" flexible duct, which goes up stairs currently. 2 duct insulation: 7,948 BTU/hour (0. Is the trunk really flex duct and not just a round sheet metal duct? I don’t even know how you do that with flex. If flexible ductwork is installed correctly, it can match metal ductwork in terms of air resistance. While he ran the duct, I cut a hole in the plenum and attached the collar. The flex duct shown above is a newly-installed foil-faced flex duct product. ) It should also step down in size after removing the first half of air, correct? Skip to main content. Unless you need to re-do the ducts in order to re-do the mechanicals, I'd give the existing ductwork a The DSC6 is used to connect flex duct to the main HVAC trunk line. As air moves from a supply plenum or main duct into a takeoff it changes direction. Branch ducts split the airflow from the main trunk duct and divert it to individual areas or rooms of a home. Reply reply Jsquared7979 The DSC6 is used to connect flex duct to the main HVAC trunk line. I tried playing around with the justification, offset heights, views (floor plan, RCP and 3D), even moving the duct for an extreme height difference but to no avail. It would be better to ourlaw it (which no one has the audacity to do). 15”/100’) • Decide how many transitions will occur along the hydraulically longest duct main (the run with The HVAC unit is responsible for your home’s cooling and heating as the weather changes. Further, the duct trunk is the chief duct, while the other minor pipes connect those pipes to the main duct. Using a . I wouldn’t accept it if the plenum is flex, it is definitely not as good as a hard ducted plenum. Although, I have done surveys prior to design where there would be flex runs of 30ft or more, but not even close to being installed correctly. A plenum in ductwork is a box that connects to the HVAC system. I could play with this some more and reduce the main trunks and add more feeders, which has the potential for reducing the total length of duct needed. No harm to the other run. These run-outs BTW, we did replace the rusted metal duct with new metal. 1 friction rate) at least a 7 inch flex duct per boot register. If you’ve noticed a spike in your energy bills without a corresponding increase in usage, your air ducts could be to blame. By guiding the height of the main duct, your ceiling height can be higher. Flex ducts extend off the loop, leading to diffusers. Some other factors to consider. Since I am redoing my main trunk as part of finishing the basement should I just go ahead an get rigid ductwork throughout? • Starting at the fan discharge, choose the duct size based on both maximum friction rate (0. This is in basement, I am using start Email Address (For your convenience, you can send the page to up to three e-mail addresses at a time. Once you've separated the inner ( Trunk Duct includes two halves 26 gauge galvanized - 60”, and 96” Lengths Furnished in Button Snaplock with S-Cleat & Drive Connections Cross Broken for Extra Stiffening Strength E-Lock The air handling unit delivers air out to a T junction on a main trunk duct loop that goes around the perimeter of the attic. Some techs and contractors swear that flex ducts are an evil invention and should never be used in ANY circumstance. For supply and return ducts, short branch duct runs, off a centrally-located trunk duct(s) is the practice recommended by HVAC industry standards. The transition off of the Rectangular Duct to the round air distribution is done with Takeoffs that are cut into the main duct. 1; Viewing 1-1 of 1. There is an existing 6" flex duct that goes form the main trunk to one and only one bedroom. Last take-off run to be located 12" - 18" from end. Each section is about 4' and there is a jog in them to prevent direct line of Rectangular trunk duct is used as the main trunk lines in HVAC supply systems. Do you own this product? Be the first to rate it. The start collar and take-off hole in the duct board trunk: We have one contractor saying that we should really replace it with a rigid trunk and only use the flexiduct to get from the main trunk to the registers, and another contractor who says all houses now use flexiduct and that we needn’t worry about the lack of a rigid trunk for a house this size. On the other hand, wallstack ducts, which are smaller in diameter, are used to distribute air horizontally to the various rooms within a building. Flex ducts are used to transport air from the HVAC system into the building. Retrofit: $6. I still don't believe in duct board. It is about 12" long, with no step down in size. I have read on these pages that each usually has a different optimal air velcoity. It can be used with 1-Inch, 1. Additionally, some of these products have higher maximum velocity ratings. I noticed he attached these flex ducts by just cutting a tight fitting hole in the trunkline and pushing the insulated duct straight into the trunkline. I do agree You really don't have to worry about your runs coming off of the main trunk and figuring them for air delivery other than for the room. Flex duct made for HVAC applications is typically constructed of a plastic inner liner attached to a metal wire helix (or coil) to make round flex duct. Once you're done, seal the hole you don't want with a metal plate, self tapping screws and that grey duct basher goo. Always stagger take-off ducts by 12″ to maintain pressure. Without it, there would be tons more labor and material to make that final connection. I'd need a 8 inch "start collar" on the trunk line to attach the flex duct to the trunk line, wouldn't I? Or is there some other way to do it? 06-21-2020, 9:01 PM #12. Musings If you have a 28’ run of 8” duct that is an extension of the main trunk AND you end that run with a boot (register), then what you have is not a BTW, we did replace the rusted metal duct with new metal. 3. (See my article on flex duct compression if you don’t believe that. If you want ever better and can give up a bit of pressure loss run the flex as a lazy S bend. Then, attach the new flex duct to the collar, ensuring a snug fit. Report. But don’t crush the inner core. 1" external static resistance for the duct-work and guessing that you have a 3 ton A/C system that requires 1200 CFM of air flow, I would estimate that the 8"X20" duct is almost fully utilized as is the 8"X8" duct. Assuming that its metal duct on especially noisy runouts when all else fails you can add 2 feet of insulated flex duct at the beginning or end of the run to dampen things down a bit. It’s easy to install. Air Terminal Devices. This is not to say you cannot get a good system out of flex duct, you can. Hard duct is probably the best but most won't pay the difference for it. Secure the flex duct to the rigid duct with duct It would depend on how far away the the duct is attached to the main trunk. 12 Inch 25 Feet Insulated Flexible Duct R4. The furnace sets perpendicular to the main trunk line which has a tee junction off the furnace output supply. The multi tap plenum is a nice touch. One of the most common methods is negative air duct cleaning, which involves generating negative pressure in the duct system by attaching a powerful vacuum, typically to a central juncture to which all main/trunk and branch ducts are connected. Use a sharp knife or scissors to make a clean cut. So I have several issues that I want to mitigate by cleaning up forced air system that takes care of my living room and kitchen. then patch and seal the bottom hole with We do engineered round metal duct trunks with flex takeoffs. Quicker to install, easier to transport and install. Does it have to be made of the same square shaped aluminum material? I actually have extra insulated flex duct in several sizes. DIY & Ideas . Runs of flex should be straight and pulled tight, not sagging, as these are. Save Up to 25% on RUUD M Series Equipment! Trunk Duct & Fittings; Sheets; Wall Stack & Fittings; Duct Hangers; I currently have, in the attic, a 2" duct board supply trunk, with interior dimensions of 12x20", giving an area of 240 in2. Always stagger take-off ducts by 12" to maintain pressure. Flex ducts can also be insulated to save energy and reduce noise. Insert the flex duct into the rigid duct. mkuxk qfcn njvgg trwzu qow dkgexo thye hjcvkc ydtnwee ctokjdng