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The best rule of thumb I have found is:

Length X Width / 144 * 288 = Max. CFM

I have used this formula to size many HVAC systems. It has always worked. For example, a 5 ton unit should have a 30x36 grille(2-18X30 filters). (30x36)/144*288=2160 max cfm.

Return Air should be sized at 200 square inches per ton according to AirMate and other filter grille manufacturers to achieve 2.0 static pressure. The Return Air Duct should have an unobstructed 6 square inches per 1000 BTU of cooling.

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Q: What size should the return air filter grill be on a 2 ton unit?
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What size should the return air grill be for a 5 ton ac unit?

Your ac contractor or engineer will determine the correct size.


If you are using a 20X20 AC filter and need to use a 20X25 where can you find the grate or register for the new filter and what is it called?

What you are refering to is called a return filter grill and there are tons to chose from, ( from ) tons of places. Home Depot, Lowes, and the likes of these places or your Heating Air/Conditioner Wholesaler close to your area. Also try typing in Central Air Return Air Filter Grills in your search bar. The Bigger the better is the rule of thumb with return air filter grills to a reasonable point . 600 cubic feet a minute is what I design air flow quantity for on my basic stuff. It is my opinion you are better off with a less expensive filter and a slower flow rate design through your return air filter grill than to use a expensive but usually highly restrictive filter in a smaller return air filter grill that is already restrictive in itself. Don't take me wrong here!!!!! ( Those Super High Quality Return Air Filters are Wonderful , usually ), Just make sure you have plenty big enough filter grill return area size to accomadate them in your system. Hope this helps: Jimiwane


How big should an air return be how many square inches per square foot of house?

Air return duct and filter grille size is dictated by the size of the unit (CFM) not the size of the house.


What size return air grill for a 36000 BTU heating system?

The size of the return air grill depends on the size of the forced air fan. The return air grid to reduce noise should be 5 to 8 times the size of the fan outlet. A 36000 btu heating system often has between a 500 to 1500 CFM fan the outlets on these fans are often between 30 and 80 square inches so the grid should be between 150 and 600 square inches (depending on the fan), the bigger you can fit the better. If you can fit it I'd put in a 12 x36 grill (432 sq in) but a 12 x 24" (288 sq inch)grill should work well too.


How do you change an AC filter?

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What size return air grill for a 60000 BTU heating system?

The size is determined by the ac contractor or engineer.


What size return air grill for a 48000 BTU heating system?

48,000 btus is equal to 4 tons of air flow, 12,000 btus per ton. You need 144 sq in per ton. Return grill should be 24x24. 48,000 btus is equal to 4 tons of air flow, 12,000 btus per ton. You need 144 sq in per ton. Return grill should be 24x24. 48,000 btus is equal to 4 tons of air flow, 12,000 btus per ton. You need 144 sq in per ton. Return grill should be 24x24.


What size return grill do you need for a 15' x 17' downstairs master bedroom - Two story 4100 sq ft two units 5 ton down 4 ton up?

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How do you calculate the amount of DE filter for a specific filter size?

The label on the Filter or the Manual should tell you. Otherwise you should be able to contact the manufacturer, perhaps via their website, to find out. It can vary depending on make and model, not just size.


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really depends on the size of the unit but if your not sure i would go with a 20x20 or a 20x25 filterback grill..


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Each air conditioner take a different size of filter. The air filter should be checked routinely and changed as needed.


What is the average size of a Cadillac Deville grill?

The average size of a Cadillac Deville Grill is listed on the site Auto Anything as being roughly 1.3 meters by 0.6 meters, though the size of a grill of course depends on the car.