• Hvac return air requirements

    Hvac return air requirements

    A vent is a vent is a vent, right? It maintains air pressure, air quality, and air circulation through your home, and also helps your system work more efficiently. And that helps you save money. Your home actually has two different kinds of air vents: supply registers and return registers. To understand why you need to know a little bit about how HVAC units work. That would cause air pressure to build up to uncomfortable levels, for one thing.

    Not only does that improve air pressure, but it also helps circulate air, keeping it fresh and filtering out dust and other particles. In fact, it even helps your unit work more effectively—as long as return registers are properly placed around your home. And when your unit is on full blast, it sucks down more energy.

    So your unit can take a load off by recycling air through your system again. That being said, there are a couple of factors you should know that play into the efficiency of your return system—and your unit as a whole. A lot of spaces simply have the main return line located in a central hallway.

    It depends on how much the return register placement affects your comfort—in some homes, you can just sense that the air feels stale and unhealthy. If you decide to stay with a limited supply line, make sure that your interior doors have large gaps beneath them so that air can flow out of the room even when the door is shut. Other design items that can affect return system performance?

    That way, when you run your air conditioning in the summertime, the return registers will be well-positioned to pull the hottest air out of a room.

    Return registers also perform best on an interior wall—not one adjacent to the outdoors.

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    The return registers could funnel off conditioned air before it has had a chance to circulate around the room. Find Reliable AC Contractors. You can also tell them apart by performing a paper test. How it works. Answer a few easy questions to get matched with the best local pros.

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    3 Things to Know About Your Return Vents

    How to Repair a Furnace Flue.InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website. How to increase HVAC system return air to increase heating or cool air output by improving the flow of return air to the air handler. This article describes problems with return air inlet size, location, and ductwork. Inadequate return air seriously limits both air flow rates and also the degree to which building air is cooled or heated by the HVAC system.

    The photograph above shows a return air inlet grille for a commercial office space after the air conditioning return register and ducts were increased in size as part of improvements in the building cooling system. How to increase air conditioning or heating return air flow to improve system performance Return air adequacy on heating and air conditioning duct systems. Adding additional return air inlets and ducts to increase airflow to the air handler is an effective way to improve air conditioning or or warm air heating system performance, provided that the system is in fact running "air starved".

    There are several easy and amateur ways to check for an air conditioning or warm air heating system that is not getting enough return air.

    hvac return air requirements

    Also keep in mind that a properly-working air handler or blower assembly will always be running with negative air pressure in the blower compartment - otherwise it wouldn't be moving any air through the duct system. So a certain amount of "pull" of air rushing into the blower that also wants to re-close the blower compartment door is normal.

    Watch out : it may be necessary to temporarily tape or bypass a blower door compartment interlock switch to try this subjective test. Don't leave the door interlock switch bypassed or taped - doing so is dangerous. Just hold a tissue or piece of toilet paper near the inlet grille face. If air is moving into the grille the tissue will be pulled against the opening.

    Sketch at left courtesy Carson Dunlop Associates. For true air flow measurements that provide quantitative results such as air flow measured in CFM. When the cooling ability of an air conditioning system is inadequate, particularly when the volume of air being delivered in the building seems too low, we often see evidence of an attempt to boost heating or cooling air delivery in this "stopgap" manner.

    We find extra return air openings having been cut in the return plenum right at the air handler unit at a combination air conditioning and hot air heating furnace or at an attic or basement air conditioning-only air handler.

    Indeed this boosts the air coming out of the system if the air handler was "air starved" due to insufficient return ducts in the first place. An example of this poor practice is shown in the photograph. But this is a very inefficient way to operate the system since a significant portion of the air volume is moving only "one way" from an attic or basement into the cooling unit and out to a remote living area.

    This is an expensive way to run an air conditioning system: keep taking "new" air, cool it, and blow it where it's wanted. Proper design re circulates air from the occupied space which permits it to be cooled and filtered. Watch out : Worse than inefficient, the approach of taking return air from a basement or crawl space utility area where gas or oil fired heating equipment is located can be dangerous, in particular if by the location of the "new" return air opening draws flue gases from a nearby draft hood or barometric damper, or if the heating equipment is located in a small enclosed space where drawing return air can interfere with the provision of adequate combustion air for the heating equipment.

    Flue gases : may be drawn into the duct system if these "improvement" openings are cut too close to heating equipment, particularly gas-fired furnaces, boilers, and water heaters.

    An HVAC system that is simply not capable of moving enough cubic feet of air per minute will not be able to adequately cool or warm the occupied space. Carson Dunlop Associates ' sketch left points out that the typical desirable rate of cool air flow in an air conditioning system is around to cubic feet per minute per ton of cooling capacity. The illustration also points out that if air flow is too slow across the cooling coil, that component may become ice or frost-blocked.

    Here we provide a list of causes of inadequate air flow, including conditions that slow the speed of movement of air through the duct system as well as other HVAC duct system defects. Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly. Just ask us!Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro.

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    We don't save this data. Google use cookies for serving our ads and handling visitor statistics. AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information. If you want to promote your products or services in the Engineering ToolBox - please use Google Adwords. Capacities of air return intakes: Air Return Intakes - Sizes and Capacities pdf Nominal Size in x in Approximately Capacity cfm 10 x 4 10 x 5 10 x 6 10 x 8 12 x 4 12 x 5 12 x 6 12 x 8 12 x 10 14 x 4 14 x 5 14 x 6 14 x 8 24 x 4 24 x 5 24 x 6 24 x 8 24 x 10 24 x 12 30 x 4 30 x 5 30 x 6 30 x 8 30 x 10 30 x 12 30 x 14 30 x 16 Screen Efficiency The free intake area will be reduced by an insect or bird screen.

    Tag Search en: air return intakes sizes capacities. Privacy We don't collect information from our users. Citation This page can be cited as Engineering ToolBox, Air Return Intakes - Sizes and Capacities. Modify access date. Scientific Online Calculator. Make Shortcut to Home Screen?A properly functioning HVAC system is essential to a comfortable home.

    hvac return air requirements

    While many people know how to operate their AC system, very few people know how it actually works. An air conditioner works by absorbing the warm air and moisture from your home. Once the dampness is separated from the air, your AC unit cools the warm air, and sends it back into your home through the return air vents. So, in a nutshell, it recycles air from each room in your home.

    Warm air travels through a specific set of ducts called a supply ductand once cooled down, it travels back to the vents through another set of ducts called a return duct. An HVAC system is basically a recirculating pump that works by heating or cooling air and then pumping it into a home. As conditioned air is pushed in, the air already in the home needs a place to escape.

    Return air vents serve this purpose by helping to pull in the air and putting it back into the system. This is what maintains proper air pressure in a home. Have you noticed dust motes circling in beams of light that filter through the windows? Homes are prone to collecting dust particles and other allergens such as pollen and pet dander.

    hvac return air requirements

    This is why you should only trust installation with HVAC professionals and conduct a home energy audit periodically. When air return vents are not working properly, the entire HVAC system suffers. Blocked vents can hinder airflow and cause the system to run inefficiently. Also, improperly placed vents can affect how a building maintains its temperature. In the infographic to the right, you can see that leaks in return vents are a common duct problem.

    Not only will this issue make your home less comfortable, but you will likely notice an increase in your monthly energy bill costs.

    The additional force inside your ducts will likely cause them to spring leaks; which, in turn, will increase your energy costs and decrease energy efficiency. Placing furniture in front of vents is also an invitation for trouble: Wood furniture will eventually become damaged and upholstered items will foster the growth of mold and mildew, especially in humid environments, such as Florida. If you have abnormally high heating and cooling costs, or your system does not maintain the desired temperature in your home, you may have a problem with your return air vents.

    Skip to content. Being an essential business, we are open and ready to serve you, however, we want to assure you that we are working to serve you safely. Maintaining Air Pressure An HVAC system is basically a recirculating pump that works by heating or cooling air and then pumping it into a home.

    Maintain Air Quality Filtering Out Debris Have you noticed dust motes circling in beams of light that filter through the windows?Remember Me?

    Results 1 to 12 of Thread: How much return air duct needed? Thread Tools Show Printable Version. How much return air duct needed? I am having a new home built on the Texas Oklahoma border. It has six inch walls and R in the ceiling. After reading on this site, I decided a dual fuel system is the way to go I have natural gas available. For some reason the HVAC sub did not like the idea. He wanted me to go total electric Heat Pump. He ended up installing a 5 ton ,Rheem 13 EER HP and a two stage, varible speed Rheem gas furnace at my request and he did it at what I considered to be a reasonable cost.

    I am not at the site very often due to the distance but the builder sends me photos. From looking at the photos, he has installed two what appears to be 12 inch return air ducts. I have attached a photo of one of them.

    hvac return air requirements

    They are both the same just different locations. My question is will this be enough for this system? I know what most of you think of flex duct but metal is way too expensive and he was wanting to gouge me even to use duct board. As I have a limited budget I agreed with his using the flex duct.

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    I am now 67 so I figure it will see me out anyway. My only concern is the amount of return air. Thanks for any input. As a 12" round duct is good for CFM, two of them would probably be just adequate, but you would have fairly high velocity when the blower is at full speed and in my experience, this means noise.

    How important is the quietness of the system to you? Larger ducts and grilles mean reduced velocities and quieter operation. What is the design CFM the subcontractor is using for the system? Check out Manual D. I wouldn't want my name on it for a 5 ton system. New home designs make it hard to get proper return but a good installer will find a way to make it happen. You can never have too much return.

    I like to see sq inches of return grill per ton. It depends on the rest of the duct system ,could be okay ,but very unlikely. Manual D as always is the way to find out.

    Other ducts could be undersized,ask to have the static tested when they start the system. Join Date Jan Location Ft.Renovating your commercial space and looking to improve your air conditioning in the process?

    When the work is done, do you want comfortable, consistent temperatures in your space? How about good air quality? Energy efficiency? If you do, then it pays to plan updates to your HVAC system and its ductwork design early in the renovation process to avoid mistakes. Find out how to improve your air conditioning with better duct design, and why you need HVAC experts involved early in your renovation process. That means air is not flowing through your space and your HVAC system as it should be, which leads to all kinds of undesirable consequences, including:.

    Proper ductwork design ensures the level of air flow that your HVAC system needs to operate efficiently and provide the comfort you want and expect in your renovated space. Here are some of the common ductwork design mistakes that impede the function of your air conditioning:.

    Contractors can make the mistake of failing to consider the type of air conditioning system you have, load requirements of different rooms, where ducts and equipment are located, and the materials used to construct them.

    All of these factors affect the proper sizing of your ducts, and getting it wrong often means your HVAC ductwork is undersized. See below for tips on getting it right. When the location of HVAC equipment and duct system and not optimized in the planning phase, the equipment may end up far away from the space to be cooled. That may require long runs of ductwork that make it hard for your HVAC system to move conditioned air to certain areas within the space.

    Just like long runs impede air flow, bends in the ductwork that are too sharp or too numerous also decrease the amount of air that actually reaches the space to be cooled. To maintain balanced air pressure and air movement, your duct system needs return vents for air in the room to be pulled back into the HVAC system.

    Not providing enough returns is a common ductwork design flaw that leads to comfort complaints. To make sure your ductwork is properly designed, start by involving a knowledgeable HVAC design professional early in your renovation design process.

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    An experienced pro will work with the architect and contractor to do the following:. Choose the best location for HVAC equipment and ducts.

    With proper planning, the HVAC equipment should be centrally located in the space to allow for the shortest possible duct runs. Ducts should be located in internal walls and ceilings to minimize the loss of conditioned air. Avoid installing ducts in attics and unconditioned crawl spaces for maximum efficiency. A detailed load calculation. Consider your equipment type and supporting systems. Certain types of air conditioning systems, like heat pumps, require larger ducts.

    Use the right materials, fittings and supports. Ductwork materials can vary depending on the requirements and the budget, but make sure your installer uses the right materials for your needs. For more information about the use of flexible ducts, read this ACHRNews article about ductwork design. If quiet operation and energy efficiency are very important to you, you might want to go with duct board, made from pressed fiberglass, which is more expensive but very quiet and efficient.

    Choose the right duct size and layout. Once all the system variables have been decided, your HVAC design professional can determine the most efficient ductwork design layout and calculate the correct duct size. Ensure proper ductwork sealing. Did you know that as much as 20 percent of your conditioned air can be lost when duct joints are not correctly sealed?

    The problem is compounded with high efficiency systems, which run longer at a lower capacity. Air is in the ducts for a longer period of time and so more can escape through leaky joints.

    Make sure your duct joints are sealed with mastic gum or metal-backed tape to prevent leaks.HVAC ductwork sizing is critical for proper heating and cooling in every room. Return air ducting is necessary in almost every room. HVAC return air improvement guide: How to increase HVAC system return air to increase heating or cool air output by improving the flow of return air to the air. In cooling only systems, we want to return that warm, stagnant air near the ceiling first. The HVAC contractor was called in to fix the problem and he.

    I knew something was wrong with my return air, since there was feet of. Then, measure the air temperature in the return duct where the return. The estimated heating and cooling loads are those required to meet the. A well-designed return air strategy is critical for the performance of the HVAC system. Get your return air grill direct from the manufacturer. David explains return grills, return grill whistling.

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    Could an AC start forming ice on the. Jones Air Conditioning talk about return duct, you need 2square. Do you know the function of the return air vent?

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    Learn more about how your AC system keeps your home cool. Some systems have additional filters inside that require professional technicians to change, but all have filters. HVAC air pathway is highly discouraged because air leakage will be very. The 20xair return is the only one upstairs that has to take care of 3. Size and capacity of air return intake. Capacities of air return intakes: air return intake.

    When the AC unit runs it always whistles air through the returns and the air. Airflow is one of the aspects of hvac that is critical — perhaps especially. The return external static pressure is measured as the air enters the return. HVAC systems should provide thermal comfort, acceptable indoor air quality, ventilation. Ducts are conduits or passages used in heating, ventilation, and air conditioning HVAC to deliver and remove air. The needed airflows include, for example, supply air, return air, and exhaust.

    A variety of flanges are available to suit various installation requirements. All internal joints are sealed with sealant. Most HVAC systems at least partially recirculate air to increase cooling or heating. Exhaust air from bathrooms are separate because they are. In addition, return vents supply more air for the HVAC system to heat or cool.

    This chapter addresses the requirements for heating, ventilating, and air.


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