Can return duct be too big? Can an air return be too big? No, an air return cannot be too big, except in extreme cases where a closed room is temporarily under negative air pressure. Return vents maintain air pressure, filter out debris, and are critical to the efficient operation of any HVAC system
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Can an air Return Vent be too big?
Can an air return be too big? No, an air return cannot be too big, except in extreme cases where a closed room is temporarily under negative air pressure. Return vents maintain air pressure, filter out debris, and are critical to the efficient operation of any HVAC system.
What happens if my return duct is too big?
What If My Return Duct Is Too Big? Bigger can be better, but there are repercussions to that also. Allowing too much air to enter the return duct can raise the amperage of the blower motor causing it to run too hot and eventually tripping the motor on an internal limit.
What is the difference between air return and supply ducts?
Supply ducts carry conditioned (heated or cooled) air into your rooms, while return ducts suck conditioned air back into the heating or cooling system through vents. Can an air return be too big? No, an air return cannot be too big, except in extreme cases where a closed room is temporarily under negative air pressure.
Do return ducts need to be the same size in every room?
With a return and supply in each room it’s important for them to be of an equivalent size so that the room is not over or under pressured. For homes that have one or two main return ducts located in a hall or a great room, those returns should be equal in size to all the supplies throughout the home.
How large should return air duct be?
16 inches by 20 inchesA typical return vent is 16 inches by 20 inches, according to Hunker. It includes the cold return air duct grille. If you consult the duct CFM sizing chart, you can quickly figure out that a 16×20 inch can handle about 1,500 CFM airflow.
What happens if ducts are too big?
The Ducts Are Too Large Eventually water will fill the hose entirely and start flowing out the other end, but the flow will be weak. Even then, it can take an hour or more for the hose to fill up entirely to the point where water will eventually be forced out.
Should return duct be bigger than supply?
Should return ducts be larger than supply? Yes, return ducts are usually larger than supply ducts to ensure that air within the home is balanced. There are generally more supply vents in the system creating the need for return vents to be larger.
Why is my return vent so big?
Your Return Vents Are Responsible for Air Pressure The return vent is usually bigger than your supply vents because it's how the air handler sucks air into the HVAC system.
Is it better to undersize or oversize ductwork?
It's better to be a little undersized than oversized, You'll get a little longer run time, but it's better than shortcycling.
What happens if there is not enough return air?
If there is not enough return air available, your HVAC system will not heat or cool properly. They must be properly sized — Return air ducts must be large enough to carry a sufficient amount of expended air back to your furnace, air conditioner, or heat pump.
Should return air be equal to supply?
Your return and supply ducts are supposed to maintain a balanced air supply. In other words, there should be an equal amount of air entering and leaving your HVAC system. If there is a difference in pressure, expect comfort and efficiency problems.
Should supply air be equal to return air?
It's not advisable to block either supply vents or return vents. This is because supply and return vents create a balance in your home. The amount of air being drawn out of your home back into your air ducts should equal the amount of conditioned air being expelled by supply vents.
Why is air coming out of my return vent?
Rooms that are far from the HVAC unit will have a lower airflow. In essence, an HVAC unit generates high air pressure. Close to the unit, the pressure will still be high, and you will see air blowing from the return vent.
How big should a cold air return vent be?
The Size Of Your Return Ducts In most cases, if you are installing ducts in each room where there is a supply, you will want to go with the same size as your supply vents. If you are installing just one or two return vents, you will want to go with a 12-inch return for 2-ton units and lower. 14- inches for 3 and up.
Does vent size matter?
Here's the answer to your question. Ducts that are small in size make your HVAC system work harder to keep your home at the desired temperature. If your duct size is big, the velocity of air gets compromised. It means you will not be able to feel the air flowing through the air vents.
Do HVAC return ducts need to be insulated?
2 Other Supply and Return Ducts. All other supply and return air ducts and plenums shall be insulated with a minimum of R-6 insulation where located in unconditioned spaces, and where located outside the building with a minimum of R-8 insulation in Climate Zone 4 and R-12 insulation in Climate Zone 5.
Does vent size matter?
Here's the answer to your question. Ducts that are small in size make your HVAC system work harder to keep your home at the desired temperature. If your duct size is big, the velocity of air gets compromised. It means you will not be able to feel the air flowing through the air vents.
What size duct do I need for a 12x12 room?
Get The Right Duct Size A 12×12 foot room will need a 4×8 inch supply duct to get an adequate CFM rate, which is about 144 CFM.
Does duct length affect CFM?
Longer ducts can increase the size of the air handler needed to supply the same cubic feet per minute (cfm), or the HVAC system may not be able to supply the designed cfm to all locations.
How many CFM is a 20x20 duct?
2,000 CFMCFM Sizing Chart For Metal Round Ducts (50-2,000 CFM)Duct Size (Inches)Metal Duct Airflow (CFM)14 inches750 CFM16 inches1,200 CFM18 inches1,500 CFM20 inches2,000 CFM7 more rows
Can an undersized return cause noise?
Yes , an undersized return will cause noise. When the return is too small the system is essentially “starving” for air. As a general rule of thumb, for a 5 ton system you should be pushing out somewhere around 2000 CFM. The current return you have is about only half of what you need, which is the cause for your noise.
Is 57 dB loud?
The velocity at the outlet would not increase. 57 db is quite loud, the article linked below explains db level and noise criteria (NC) when selecting grilles. NC < 30 is pretty good for grilles. Just increasing the grille size will help but a good portion of your noise could be coming from the unit itself. Can you measure the size of the return duct and length to the unit.
What Happens If My Return Duct Is Too Small?
Several things are effected by duct work that is too small. One of the most noticeable characteristics of small ducts is noise. Your furnace has this static pressure designed to deliver quiet and efficient heating and cooling. Just the right amount nice quiet air in, out and through the system.
How to determine the size of ductwork?
Basically the size of your duct work is determined by the size of your furnace. You size your furnace to be large enough to heat your home, and that furnace pushes or delivers so much airflow to keep the furnace from overheating. Go look at your furnace’s factory label and look for the part on that label that’s giving a number for “external static ...
Why does my squirrel cage blower run hot?
Allowing too much air to enter the return duct can raise the amperage of the blower motor causing it to run too hot and eventually tripping the motor on an internal limit. A squirrel cage blower has the characteristic of drawing higher amps with the more air that it can grab.
Why is it important to have a return and supply in each room?
With a return and supply in each room it’s important for them to be of an equivalent size so that the room is not over or under pressured. For homes that have one or two main return ducts located in a hall or a great room, those returns should be equal in size to all the supplies throughout the home. Basically the size of your duct work is ...
Should return ducts be larger than supply ducts?
Should A Return Duct Be Larger Than Supply Ducts? In a rule of thumb sense the return duct should be the same size as all the supply ducts combined. But a rule of thumb is just an initial guide, not anything to bet your comfort on. You have to consider the length of duct and the type of duct.
How long should an AC run on a 90 degree day?
A properly sized AC system, in say Seattle for instance (design temp is 85 degF) should run about 18 to 20 hours on a 90+ degree day. However, when an AC unit does run that much on a design day, contractors invarialbly get complaints about the system being too small. So, they pad it a little adding an extra 1/2 ton or 1 ton, to CYA. That is most likely the reason for the range in sizes proposed.
What does "go with correct size" mean?
Go with correct size. Sizing is a function of the output, size of unit and other factors. When all else is figured, going with a larger than required duct work will or can reduce the effectiveness and efficiency of the system
Will a larger duct have less noise?
3. "..will larger duct have less noise.."? Yes and no. During constant, continuous air flow, the lower the velocity, the less friction and noise will be experienced. However, during transients, especially fan start-up, the larger the surface area of the inside of the duct, the greater the chance of "oil canning", that "tink" noise when air pressure causes the duct to flex a little. Also, duct noise is usually small compared to the other noises in a forced air system: fan/blower noise, inducer noise, burner noise and noise at registes and grilles.
Can a competent contractor show load determination?
As far a the unit (s) capacities are concerned, each competent contractor can and will show you their load determination for their selection (s). If not, consider that a big red flag, and a deal killer (IMPO).
Do I need to speed the air that the smaller duct would give?
2. "..do i need to speed of the air that the smaller duct would give." No, velocity inside of ducts (commercial kitchen exhaust ducts/grease ducts are a very specific exception) need not meet any "minimum". Cost and size constraints dictate that ducts be as small as possible. Pressure drop and noise dictate that ducts be as large as possible. Design, is partially a process that takes the two conflicting "needs" and makes suitable compromises.
What is the effect of larger ducts on air flow?
Larger ducts reduce the velocity of the air.
How to fix static in ducts?
Oversized ducts,too low of a static ,can usually be fixed by adding dampers ,to increase the static and redirect the air flow,as needed.
What would happen if a fan was allowed to run with no resistance?
If a Fan where allowed to run with no resistance it would be at its Max CFM with no Static pressure (0 In. Wc)
What happens if you take a blower out of a furnace?
If you take a blower out of the furnace it will overload the motor. Depending on its SP rated design, too high an SP will cause the blower wheel to unload.
Which is more efficient, a blower motor or an air handler?
1) Generally speaking, blower motors are more efficient at lower esp's, given the same airflow, as long as you're operating above the min recommended esp for the air handler.
Can you balance an oversized duct?
Finally, balancing, which is indeed important, can be accomplished with an oversized duct system in the same way as with a 'properly' sized duct system (e.g., by selecting correct relationships between various trunks, run-outs and difussers, and if necessary, using balancing dampers). See my earlier response, above.
When is a heat load inadequete?
the only time a heat load is inadequete is when the heat load is performed by an unqualified person wheather or not hes been doing it 20 years or 1.
