The Size Of Your Return Ducts 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. 16-inch should be suitable for 4 ton systems, whereas 5 might require 18-inch returns.
An approximate rule of thumb to use when engineering data is not available is to multiply the filter grille area in square inches by 2 CFM for each square inch. This should keep the face velocity of the filter grille below 400 FPM.
Our temperature has always been tough to keep constant throughout the house and we have recently been told more square inches of return vents would help with this problem. Thanks. 125 sq inches of Return air per ton is a good standard to go by. 125 sq inches of Return air per ton is a good standard to go by.
Ductwork that Delivers. Use the “Rule of Two Feet” • No take-offs within 24” of trunk end-cap, • Never locate a takeoff in the end-cap, • Limit trunk-lines to 24 ft in length.
Typically a 16X20 would be fairly standard for most applications on a 3 ton unit. However if you want superior air flow I would highly suggest putting in a 20X20 as that gives you far better airflow hands down.
If the return duct is too small or there are an inadequate number of return grilles, your HVAC system won't be able to return enough air to recirculate into the system. Again, it's like if you were breathing in through a straw while jogging.
Homes measuring 1,000-1,500 square feet: You'll need a 2-ton unit, which corresponds to a cooling capacity of 24,000 BTUs per hour. Homes measuring 1,500-2,000 square feet: You'll require a 3-ton unit, equivalent to 36,000 BTUs per hour. Homes measuring 2,000-2,500 square feet: A 4-ton unit is necessary.
Rule of Thumb – The maximum size unit you should buy would be 15% over the BTUs you need for cooling and 40% of the BTUs for heating. The max for heat pumps is 25%, since it handles both cooling and heating. Your local climate and weather conditions play a significant role in determining the right HVAC size.
Returns placed within 4' of a supply will not suck supply air over to it, due to a return having little large scale effect on air movement in a room. This is said with the understanding that the supply air is not being thrown toward the return, as might be possible with poorly aimed three-way supply registers.
When setting up a ventilation system we typically figure a 7% loss in CFM for every 25 ft. when using flexible ducting (a 3% loss if using metal duct pipe). You should also factor a 3% loss for every 90 degree bend in your ductwork.
They are usually located in central, larger rooms to more efficiently pull air from the home and into the system. Return air vents are often located on a wall, rather than the floor or ceiling. Air return vents play a critical role in balancing the air in your home.
Insufficient return air can lead to higher energy bills. When your HVAC system doesn't receive enough return air, it must work harder to maintain the desired temperature, increasing energy consumption. Homeowners might notice a spike in utility costs without a corresponding increase in usage.
Undersized return ducts can cause up to 20% of the conditioned air in your home to escape. This occurs due to air pressure and not a hole in a duct. The excess pressure is caused by exhaust air staying in a room longer. The room may become uncomfortable and stuffy.
In most applications, the door undercut would need to be 1.5 inches or greater to allow enough air to pass. There are some through-the-door alternatives that can be effective.
The Size Of Your Return Ducts
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. 16-inch should be suitable for 4 ton systems, whereas 5 might require 18-inch returns.
What room should return air ducts not be installed? Return air ducts should generally not be installed in rooms with high humidity or areas prone to moisture accumulation, such as bathrooms or kitchens.
While return vents don't always require filters, adding them provides additional filtration, improving indoor air quality and keeping dirt and debris out of your system.
Since an oversized AC is too powerful for your home, it will quickly cool your home then shut off, which can raise your energy bills and wear out your AC (from all the starts and stops).
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. There is an assumption of an 8-ft ceiling, no unusual window areas, and average insulation.
The thumb rule for air conditioning sizing is mostly used when there's a temporary cooling requirement because they are quick and easy. The thumb rule uses 500 square feet per ton to calculate the size of the air conditioning system.
Neither oversizing nor undersizing your AC unit is ideal. Both scenarios can lead to issues with efficiency, comfort, and longevity of the system.
HVAC Pro Cost
Most people pay $500 to $2,500 in labor for AC replacement.
For most homeowners: Hot Climates (Texas): A 17-18 SEER unit with a variable-speed compressor provides a great balance of comfort, efficiency, and cost. Milder Climates: A 14-16 SEER unit is often sufficient.