# I would like to know while designing of duct how will i calculate the cfm Air discharge in units like CFM through a collar opening? What is the formula for giving the collar size for air discharge. Lets for Example I have a AHu of Capacity 1200 CFM I have to distribute the total cfm equally through duct on three seperate room . then what will be the duct collar opening for each room so that each room will get 400 cfm each? RegardsM.A.Shah09314545556

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You'll have to pay for that info..

Posted on Jun 20, 2009

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## Related Questions:

### How do I convert the CFM output to tonnage? Thanks much!

CFM is air flow, a product of fan size and speed and duct size, opening sizes etc.. The tonnage of the unit has no bearing on airflow.

Apr 01, 2015 | Cfm Heating & Cooling

### 35,000 cfm = ?pounds trust

There is no equivilancy between the two...pounds of thrust would be 'foot pounds of torque' and cfm is the amount of air delivery is passing a specific sized opening in cubic feet per minute.

If you are looking at how much pressure is in for instance a residential air conditioning system, they are typically designed for .5"w.c. total system static. Meaning the pressure in the supply air duct plus the negative static added together cannot exceed .5" of water column. Approximately 28" w.c. per pound of pressure and we don't want any more than 1/2 of one inch water columm....

Now if you're talking about turbo-chargers....thats a different story and I haven't a clue.

Mar 04, 2015 | Cfm Heating & Cooling

### I'd like to know what its cfm? THank you.

Hi,
CFM is short for cubic feet per minute....
It is usually used in relation ship to air movement...
It is a unit of measurement for the amount of air that it moving through say a furnace, blower, or duct...

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Jan 16, 2011 | Microwave Ovens

### What is and how is find out cfm for 5ton air conditioner

12000 BTU is 1 ton
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Cfm means air flow per cubic meter per hour.

Dec 14, 2010 | Cfm Daikin R410a Split System Air...

### How do you calculate cfm for a room when sizing a hvac system fr a residential

their is a chart that homedepot use to give in a/c dept may still be their but a 6" run is about 100 cfm this will cover 10x10 1 sq inch is 1 cfm 1 ton is 400 cfm a gas system is 400 per ton and a heat pump is more like 425 but is best to figure the 400 cfm for both say you got 12x10 room that is 120 sq ft so you need around 120 cfm and if the 6" duct is 100% hard pipe with no flex you can get that if you balance your air if more help is needed email pendletonheatandair@hotmail.com please give me a vote and rating

Sep 22, 2010 | Cfm Heating & Cooling

### How to properly size a duct return in a house

Hi,
To size that return duct you need to know the cfm of the unit, and size according to that...Ell's and distance also need to be factored in....
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Here is a website that will let you get a free trial duct calc.

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Sep 21, 2010 | Coleman Heating & Cooling

### Have an Chrysler Corporation central station air

Owner found the original set of design drawings. Added up the total cfm of the outlets, and modelled the duct system to find the design static pressure. At this stage of it's life, we're limiting the AHU to only 3/4 of design load.

Nov 14, 2009 | Heating & Cooling

### Calculation of CFM discharge from an opening of a duct collar

There's a thumb rule in A/C air distribution. At 1 TR load, the air supply is about 400 CFM and the ideal diffuser size is 16" x 16" with an effective flow area of about 70%. Branch duct size for this outlet should be around 12" x 12".

Jun 20, 2009 | Carrier Heating & Cooling

Here are a few ways to calculate your BTU's.
Get ready to use that algebra you thought you'd never use.
1 Ton = 12000 BTU's
400cubic feet per minute (CFM) = 1 Ton on standard ac units (300 is an absolute minnimum)
BTU's air heat = difference in temp. ( ∆T ) x 1.08 x CFM
∆T = BTU's / (1.08 x CFM)
i.e. 65F entering your unit and 93F air leaving on a 12000BTU unit.
∆T = 28
CFM = 400
28 x 1.08 x 400 = 12096BTU's
Another way...
Electric heat calculations.
BTU's = KW (killowatts) x 3413
Watts = Volts x Amps (single Phase) Most Homes))
Watts = Volts x Amps x Phase (this is for three phase units.)three wires and a ground))
120 volts 30 amps single phase (common)
120 x 30.0 x 1 = 3600 or 3.6KW 3.6 x 3413 = 12286BTU's

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