What size flex duct for a mobile home? As long as the size is about diameter, the ideal size for a mobile home is 12” of flex duct. You can go for thicker ones like 14” or 16”, but your mobile home floor should be higher than usual in that case.

How do I know what size flex duct I need?

One simply needs a ruler or measuring tape along with the end of the hose or outlet. Keep in mind that you have to begin the measurements from the interior wall of the circle. The distance to the opposing point of the circle is the measure of the flex duct sizing for the inner diameter.

How do you know what size ductwork to use?

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.

How many CFM does a 7 inch flex duct?

110 CFM Duct Size (Inches) Flex Duct Airflow (CFM) 6 inches 75 CFM 7 inches 110 CFM 8 inches 160 CFM 9 inches 225 CFM.

How far can you run flex duct?

Flexible duct shall be supported at manufacturer’s recommended intervals, but at no greater distance than four feet. Maximum permissible sag is 1/2 inch per foot of spacing between supports.

What size ductwork do I need for a 3 ton unit?

Multiply the tonnage, 3.5, by the total BTU per ton and this will give you the total BTU rating. Multiply 6 x 42 to determine the duct size of 252 square inches The clear are of the duct must be at least 252 square inches This measurement also includes the opening in the floor at the bottom of the return.

What size ductwork do I need for a 5 ton unit?

Using this approach, two 20-in. x 25-in. return grilles will be the right choice for a five-ton HVAC system in order to actually deliver 2,000 cfm back to the blower without causing the return to hemorrhage.

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 happens when you reduce duct size?

The key takeaway here is that air moves from a larger to a smaller duct, the velocity increases. When it moves from a smaller to a larger duct, the velocity decreases. In both cases, the flow rate — the amount of air moving through the duct, in cubic feet per minute — stays the same.

Does register size matter?

Unless you are severely undersizing your register, the noise is really the only issue. So a bigger register will not help cool or heat your room better. Putting the register in a better location and making sure the air is shooting out in an efficient manner and at an efficient angle is key.

What size duct is needed for 1000 cfm?

Rectangular equivalent diameter for air flows between 100 – 50000 cfm. Air flow – q – (Cubic Feet per Minute, cfm) (m 3 /s) Rectangular Duct Sizes (inches) (mm) x (mm) Friction Loss (inH 2 O / 100 ft duct) (Pa/100m) 1000 (0.45) 10 x 14 12 x 12 0.15 1300 (0.59) 12 x 14 0.15 1400 (0.63) 12 x 15 0.15 1700 (0.77) 10 x 22 14 x 15 0.14.

How many CFM is a 4 inch round duct?

Reviewing the chart, a 4” pipe will convey 395 CFM at 4500 FPM. This means that a 4” pick-up on a machine will use 395 CFM from the filtering system; or, if you know that a machine will require approximately 400 CFM to remove the waste, you should use a 4” pipe for that purpose.

What happens if ductwork is oversized?

The Ducts Are Too Large Not much. This is what happens when your air ducts are too big for your system. Your system pushes air into the ducts, but the ducts are too large for it to build up any sustained amount of air pressure, and thus a “forced air” system doesn’t have any force.

Does Flex duct reduce airflow?

Friction is the enemy of airflow. Unlike rigid ducts, which are cut to length within a tolerance of 1 inch or less, it’s easy to cut a length of flexible duct that’s several feet longer than is needed to get from point A to point B [2A]. That creates slack in the duct, which reduces airflow for two reasons.

What is the minimum length in which flex duct should be ran?

The proposed code language It says, “Length limitation: Factory-made flexible air ducts and connectors should not be more than 5 feet (1,524 mm) in length and shall not be used in lieu of rigid elbows or fittings.”.

Should I replace metal duct with flexible?

Flex ducts are better for existing trunk-and-branch heating and cooling systems. Metal ducts are more rigid due to the nature of steel, making them ideal to build an entire HVAC system. Installation. In comparison to metal duct, flex duct is easier and faster to install.

How many CFM is a 3.5 ton?

How many cfm for 1 – 5 ton ac unit ? Cooling Capacity CFM (Airflow) How many CFM is a 2 ton ac unit? 700 – 800 CFM How many CFM is a 2.5 ton ac unit? 875 – 1000 CFM How many CFM is a 3 ton ac unit? 1050 – 1200 CFM How many CFM is a 3.5 ton ac unit? 1225 – 1400 CFM.

Can a return air 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.

What size duct do I need for a 2.5 ton AC unit?

For instance a 2.5 ton system (Approximately 400 CFM per ton) would require (2) 14” flexible return ducts or (1) very short flexible 18” duct to move the 1000 CFM required by the 2.5 ton system.