View Full Version : Calculating cfm
03-25-2012, 02:29 PM
Does anyone have a affordable solution for calculating cfm for a/c units?
03-25-2012, 02:33 PM
Calculating CFM for indoor blower?
Total External Static..
Use blower chart in paperwork that came with furnace to see what CFM you are pushing with that static pressure at which fan speed.
Very easy, just use your manometer..
03-25-2012, 03:04 PM
What do you do if charts is not with heater?
03-25-2012, 03:13 PM
go online and get the paperwork for that unit.
03-25-2012, 04:22 PM
If you've got electric heat you can use the temp. rise method.
03-25-2012, 05:10 PM
Can always call whoever makes the unit, speak with tech support and they can tell you your cfm with your total external static pressure, and which blower speed you are on. Get that info first, and obviously Model/Serial of air handler. Type of coil is helpful also.
03-25-2012, 06:04 PM
as long as you have the ability to run in heat mode.
output btu / temp rise * 1.08 = cfm
Run the heat in the cooling speed.
If electric heat, then kw * 3.414 / temp rise * 1.08 = cfm
run the fan in cooling speed.
Furnace output = input * efficiency
100,000 btu in * .8 (80%)
80,000 btu output furnace / 50 deg rise * 1.08 = 1481 cfm
80,000 btu output furnace / 60 deg rise * 1.08 = 1234 cfm
So the higher the rise, the less the flow.
03-25-2012, 08:26 PM
Heating man thank you for the breakdown that simplifies it big time.
03-26-2012, 09:20 PM
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