We sell a comprehensive range of air plenum boxes to suit Daikin split system and VRV ceiling concealed ducted air conditioning systems. Please use the drop down menu to find the above ceiling ducted indoor unit that you are installing - a velocity calculator above also assists you in the selection of the correct air outlet configuration. English English French. My Account. Orders Wish list Track my order s. Track my order s.
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Quick view. Daikin Plenum Box. My account Sign in Create account. Linwood About us Contact us Sitemap Blog.Remember Me? Page 1 of 2 1 2 Last Jump to page: Results 1 to 13 of Thread: Correctly sizing a supply plenum. Thread Tools Show Printable Version. Correctly sizing a supply plenum.
New to the business and need help. I am trying to properly size a supply plenum. I am very new to the business so variable speed blowers and 2 stage compressors are beyond my scope. Problems are comfort issues entire house, not room specific. Very long run times. Very high utility bills. Ho has had installing company out multiple times "12" and they say nothing is wrong but have adjusted blower motor and added 2 returns since the complaints started.
Original unit was 3 or 3. What I found. Very leaky duct system "in this case I think probably a good thing.
Returns not too bad. ESP 1. Flex is R Plenums and ducts except for the added returns and 1 supply are from the original system. Returns 16, Supply's 7, 7, 8, 10, 10, the second 10 was added.
My plan was to enlarge the plenum and add a couple of duct runs.One of a series of dealer contractor technical advisories prepared by HARDI wholesalers as a customer service. A box plenum is a wide but short-length duct used to supply conditioned air to multiple branch ducts.
The branch run-outs may be insulated flexible ducts or insulated round sheet metal pipes. The box plenum is frequently the principle supply plenum for a small residence, but may also be used in sub-circuits of larger distribution systems.
The design information outlined in this Tech Tip is based on research conducted at the University of Illinois. The results of that investigation showed the pressure loss imposed by box plenums was significant and must be considered in the overall system design. It was also determined that a special splitter vane entrance fitting was necessary to eliminate unstable air rotation within the plenum and to keep plenum pressure loss to a reasonable value.
You must be familiar with the procedures in Manual D or its equivalent to complete the design. This tech tip provides a means to estimate the pressure loss of the box plenum in combination with any supply trunk between the conditioning unit and the box plenum. Recommended box plenum proportions are listed in Figure 1.
Optimum plenum width is 2. Box plenum width may vary from 2 to 3 times the opening width. The preferred box plenum length is two times the plenum width, but may vary from 1 to 3 times the plenum width. Note minimum clearance requirement between first branch take-offs and the entrance to the box plenum. Figure 2 shows the construction dimensions for the special entrance fitting.
Tests have shown that without this fitting, air will first rotate clockwise within the plenum. Then, with an off-on cycle of equipment, air rotation may reverse and rotate counterclockwise.
This changing direction affects the amount of air delivered to each branch and can upset the balance in the system. Use of the special fitting also reduces the box plenum pressure loss by as much as 80 percent. Any supply trunk duct between the conditioning unit and box plenum is sized based on the supply system CFM and acceptable air velocity of from to feet per minute fpm.
The effective length of the supply trunk if one is used is determined based on the measured length of the trunk and the equivalent length of any fittings used in the supply trunk.
Equivalent length values for fittings are listed in Manual D. Example: A conditioning unit is to supply CFM through a short supply trunk and box plenum with 9 run-outs. Figure 3 shows the arrangement. A supply trunk air velocity of fpm is selected. Assume a 16 in. This is also the size of the opening in the box plenum.
How to Properly Size Box Plenums
The measured length and fitting equivalent lengths of the trunk total 20 ft.Get free estimates from local Supply Air Plenum contractors. Before understanding the costs associated with buying and installing supply air plenums, homeowners need to know how they function. A supply air plenum is a metal box that can be attached to the outlet of a furnace. It can also be attached to an air handler. These metal boxes are used as a central manifold for all of the ductwork to connect to.
When air blows out of the air handler or furnace, it will pass through the supply air plenum and then to the ductwork that is attached to it. The cost of supply air plenums depends on the size of the supply air plenums that are purchased. Homeowners will need to pay attention to what size supply air plenums correctly attach to their furnaces. If a homeowner is unsure, the contractor hired to install the supply air plenum will be able to assess the system.
The other cost for the homeowner to consider is labor for the installation. It is important that supply air plenums are installed correctly, which is why most homeowners should opt to hire a professional contractor.
This does not include the price of buying the supply air plenums. The materials needed to install a supply air plenum vary depending on if the unit is an internal or external unit. Either way, it is usually a good idea for the homeowner to let a professional install it to make sure that everything is done properly.
Keep in mind that not all of these tools or materials will be needed for all projects. Only a professional contractor can inform the homeowner as to what materials will be needed.
The biggest pro to a supply air plenum is that it enhances the function of almost all furnaces. This unit connects the duct work to the furnace itself. Without it, the furnace would be unable to deliver air to the entire house. How often a supply air plenum is going to need to be replaced will differ depending on the quality of the material purchased by the homeowner or contractor, but homeowners who do their research can find low-maintenance units.
Because supply air plenums are needed to connect the furnace with the duct work to transfer air around an entire house, some models can be expensive, especially when size is considered.
Some furnaces require larger supply air plenums than others. This can greatly increase the cost of installing the air supply plenum. These units are needed for a furnace to function, so the only factor that the homeowner can change to control the cost is the quality of the unit purchased. Get Free Quotes. Cost of Supply Air Plenums. Get Started! Get Local Cost. Start a Similar Quote.This Hvac For Beginners section begins here with a discussion about forced air duct systems, the basics, the how and why of duct sizing.
Ductwork is simply an air delivery system. A delivery system for all forced air systems, furnace or air handler, heating or air conditioning, or both.
Duct delivers fresh air and humidification into your home. Ductwork is the channel through which the air in your home is filtered and purified, or expelled to the outdoors and replaced with fresh new air. Each component of the ducted air delivery system, from the air handler to the registers, adds a certain amount of resistance to the airflow. This resistance is friction loss.
Manual J gives us the room-by-room airflow requirements. Manual S gives us the blower that will provide the required airflow.
Manual D provides the ductwork sizing to ensure balanced airflow all the way to the registers. All duct fittings, ells, tees, reducers, take-offs, etc. Even the straight ductwork in a system adds a certain amount of friction loss. Calculated friction loss equates to equivalent duct length. Manual D takes each component's equivalent duct length and adds them together for TEL total equivalent duct length.
Above and below are examples of simple hvac duct systems.
The diagram above illustrates the fact that the air handler may be centrally located preferredor located elsewhere dependent upon the configuration of your home. Duct sizing for the two examples would certainly be very different.
Other fairly common systems can be underslab or crawlspace, with a counterflow or downflow air handler, attic or crawlspace systems with a horizontal air handler. The ducting is actually quite similar. Supply Plenum - usually on top of air handler for the initial distribution of conditioned air through connected ductwork.
Return Air Drop - brings air from living space to air handler for conditioning and re-distribution. Flared Rectangular Take-off - connects to plenum to start ductwork. Reducer - usually 3 or 4 supply branches are connected to main trunk before a reducer changes duct size. Can be rectangular, square, or round. Top Take-off - connector for round branch lines to connect to main supply trunk.
Can be square-to-round, oval-to-round, or round-to-round. Often are used as side take-offs also. Boots - delivers conditioned air into living space and houses the register. Stack head - a boot for a wall register.
Wall stack - ductwork inside a wall to feed a stack head. Panning - flat metal nailed to joists for return air.
Outside Air - Often a free flowing outide air is tied into the return ducting to keep some fresh air introduced into the residence. In extreme climates this ducting must be insulated, or condensation will occur. Site Build It! Site Navigation. Copyright - perfect-home-hvac-design.Properly sizing and installing your air conditioning system are important in making sure your air conditioner operates efficiently, according to the U.
Department of Energy. One thing to remember is that you must have enough supply vents vents blowing air out and return vents vent sucking warm air back in the air conditioner. Also, improper duct installation will impact your air conditioner's efficiency and your electric bill. Look for the data tag on the outside of your condenser outside unit to determine the size of your air conditioner example: 3 ton.
Calculate the return duct size based on the air conditioner's size and the type of duct you are using. Use the following formulas:. Calculate the square root of the total.
How to Size an Air Conditioner Return Air Duct
The square root of is Therefore, your return air duct and grill size will be 24 by 24 inches. Julie Boleware has been writing since She has been published on the Internet Public Library and various websites.
Boleware's interests are in arts and entertainment and business. Hunker may earn compensation through affiliate links in this story. Step 1.
Step 2. Decide if you'll be using round or rectangular duct. Step 3. For round duct: Diameter of duct x 3. Step 4. Tip Always place return ducts as far away from the supply air vents as possible. Department of Energy; Energy Savers. Share this article.A household forced-air heating, ventilation and air conditioning system depends on a system of ducts to provide a controlled path for distributing heated or cooled air throughout the home.
Typically, HVAC duct systems are made of sheet metal, but other rigid heatproof materials such as fiberglass or insulated plastic may be used. Regardless of construction material, the heart of an HVAC duct system is the plenum. A plenum is an air-distribution box attached directly to the supply outlet of the HVAC equipment that heats or cools the air to make the house comfortable.
The ductwork that distributes the heated or cooled air to individual rooms of the house connects to the plenum. The HVAC equipment has a blower that forces heated or cooled air into the supply plenum and from the plenum into the rooms through the supply duct system. Air-cleaning filters may be located in the supply plenum. Forced-air systems also have return ducts that connect to the HVAC equipment through an air-collection box known as a return plenum.
The air from the rooms collects in the return plenum and is drawn back into the HVAC equipment through the return inlet for another round of heating or cooling. Air filters often are located in the return plenum.
Herb Kirchhoff has more than three decades of hands-on experience as an avid garden hobbyist and home handyman. Since retiring from the news business inKirchhoff takes care of a acre rural Michigan lakefront property and applies his experience to his vegetable and flower gardens and home repair and renovation projects.
What Is a Plenum in an HVAC System?
Skip to main content. Home Guides Home Home Improvement. About the Author Herb Kirchhoff has more than three decades of hands-on experience as an avid garden hobbyist and home handyman. Customer Service Newsroom Contacts.