How do you calculate duct size?
To calculate the required equipment size, divide the HVAC load for the entire building by 12,000. One ton equals 12,000 BTUs, so if a house or office needs 24,000 BTUs, it will take a 2-ton HVAC unit. If you get an uneven number, such as 2.33 for a 28,000 BTU load capacity, round up to a 2.5-ton unit.
What size duct do I need for 2000 cfm?
Rectangular equivalent diameter for air flows between 100 – 50000 cfm.
| Air flow – q – (Cubic Feet per Minute, cfm) (m3/s) | Rectangular Duct Sizes (inches) (mm) x (mm) |
|---|---|
| 2000 (0.9) | 10 x 25 12 x 20 15 x 16 |
| 2500 (1.13) | 14 x 20 15 x 18 |
| 2800 (1.26) | 12 x 26 16 x 20 |
| 3300 (1.49) | 12 x 30 14 x 25 |
What does a duct calculator do?
It isn’t a measurement tool. The air duct calculator is for design only. To determine airflow in a duct by pressure, you need to measure velocity pressure, not static pressure. Velocity pressure is measured with a Pitot tube at multiple points in the duct using a traverse procedure, which is converted to air velocity.
What size duct do I need for a 12×12 room?
A 12×12 foot room will need a 4×8 inch supply duct to get an adequate CFM rate, which is about 144 CFM.
What is the good rule of thumb in sizing ductwork?
In the simplest of terms, the rule of thumb states – for every 500 square feet of air-conditioned floor area install an AC of one-tonne capacity. Why Does Duct Size Matter? One thing pretty clear is that you need to have appropriately sized ducts for the HVAC to work effectively.
What size duct do I need for 1600 CFM?
12-Inch Rectangular Ducts Size Chart (150-3,050 CFM)
| 12″ Duct | 12″ CFM |
|---|---|
| 20×12 | 1,250 CFM |
| 22×12 | 1,400 CFM |
| 24×12 | 1,600 CFM |
| 26×12 | 1,750 CFM |
What size duct do I need for 3000 CFM?
The biggest 42×12 ducts with 504 sq inch crosssection can handle 3000+ CFM airflow.
How many CFM is a 3 ton AC?
1200 CFM
A 3-ton heat pump has approximately 1200 CFM of air flow.
How many CFM do I need per room?
One cfm is needed per square foot (1 cfm/sq ft) of floor area. This is the average air quantity required for a room or an entire building. This number is based upon an averaged heat load calculation for comfort cooling.
How many CFM is a 12×12 duct?
680 CFM
12-Inch Rectangular Ducts Size Chart (150-3,050 CFM)
| 12″ Duct | 12″ CFM |
|---|---|
| 6×12 | 270 CFM |
| 8×12 | 400 CFM |
| 10×12 | 550 CFM |
| 12×12 | 680 CFM |
Does reducing duct size increase pressure?
Undersized Ducts
If your ducts are too small to accommodate the air flowing through them, the pressure increases and backs up in the system. This causes resistance for the blower fan, reducing your HVAC system’s efficiency and longevity.
What size duct do I need for 3000 cfm?
What size duct is needed for 1200 CFM?
10” diameter
The higher the cubic feet per minute, the larger the duct you’ll need. At 600 CFM, the minimum duct size is 6”. At 900 CFM, the minimum duct size is 8”. Finally, at 1200 CFM and above, consider a 10” diameter duct or larger.
How many CFM can a 6 round duct handle?
The smallest 6×4 ducts can handle 60 CFM airflow. The biggest 42×12 ducts with 504 sq inch crosssection can handle 3000+ CFM airflow.
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6-Inch Rectangular Ducts Size Chart (60-775 CFM)
| 6″ Duct | 6″ CFM |
|---|---|
| 6×6 | 110 CFM |
| 8×6 | 160 CFM |
| 10×6 | 215 CFM |
| 12×6 | 270 CFM |
How many CFM is a 3.5 ton AC?
1,400 CFM
How Many CFM For 1 – 6 Ton Units? ( Chart)
| Unit Tonnage: | CFMs Required: |
|---|---|
| 3.5 Ton Unit | 1,400 CFM |
| 4 Ton Unit | 1,600 CFM |
| 4.5 Ton Unit | 1,800 CFM |
| 5 Ton Unit | 2,000 CFM |
What size duct work do I need for a 3-ton unit?
As a general rule, the supply duct size for a 3-ton AC is as follows: Round duct – 16″ diameter. Rectangular duct – 16″ x 12″ or 20″ x 10″ or 24″ x 8″
How many CFM do I need for a 2000 square foot house?
Heat and energy recovery ventilators
| Total area of home (square feet) | Continuous ventilation rate |
|---|---|
| 1,000 square feet | 50 CFM |
| 2,000 square feet | 100 CFM |
| 3,000 square feet | 150 CFM |
How many CFM does a 6 inch duct have?
A rectangular 6×6-inch duct has an airflow of 110 CFM. Bigger 6×12-inch ducts can handle 270 CFM airflow. The bigger the crosssection of ducts, the bigger CFM; that’s pretty obvious. The smallest 6×4 ducts can handle 60 CFM airflow.
How many CFM is a 20×20 duct?
2,000 CFM
CFM Sizing Chart For Metal Round Ducts (50-2,000 CFM)
| Duct Size (Inches) | Metal Duct Airflow (CFM) |
|---|---|
| 14 inches | 750 CFM |
| 16 inches | 1,200 CFM |
| 18 inches | 1,500 CFM |
| 20 inches | 2,000 CFM |
What happens if your ductwork is undersized?
Ducts that are undersized will increase the static pressure, which will result in excessive noise as air moves through the system. It is often loud enough to be distracting, so it will not be difficult to overlook and should be addressed, as undersized ducts overwork the heating unit.
How many CFM is a 6 inch round?
75 CFM
CFM Sizing Chart For Flex Round Ducts (50-1,700 CFM)
| Duct Size (Inches) | Flex Duct Airflow (CFM) |
|---|---|
| 5 inches | 50 CFM |
| 6 inches | 75 CFM |
| 7 inches | 110 CFM |
| 8 inches | 160 CFM |
How far can you run 6 round duct?
When you go from 6″ round to 6″ oval, you get 110′ of equivalent length. Wow! That means that a fitting that is somewhere around 1′ in actual length reduces the air flow as much as 110′ of straight 6″ duct.
Does duct length affect CFM?
Excessive Length
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.
What size supply duct do I need for a 4 ton unit?
The right size of return duct for a 3.5 ton AC is 22 X 22 inches. In the case of a 4 ton AC, it’s 24 X 24 inches. And for a 5 ton AC, the correct size is 27 X 27 inches.
How many CFM do I need for a 3000 sq ft house?
A big 3000 sq ft house requires much bigger whole house fans, with airflow generating ranging from 1200 CFM to 2400 CFM.