How many CFM's are my furnace pushing. It's a 383KAV, 1/3 h.p. blower. Cooling is on the high tap and the heating is on the low tap. Thanks.

I would need more information.. like size of unit and static pressure. Although the second one is not one you will get without having a tech out. Also it changes with the type or style of filter used.

I have no idea how to find out this info.

Get me the whole model number of the unit and I can find the correct sizing for it. As far as the rest you need tools and a trained tech to do it.

Bryant 383KAV036070 gas upflow furnace

You will need your complete model number. Then find it in the last chart. Then calculate your static pressure of your duct system for a final calculation. These units do require knowledge of HVAC and the proper tools for a final setup or damage to the blower motor OR heat exchanger can result. siberianair mentioned this in his post.

http://www.ackleysheetmetal.com/bryant/gas_furnaces/00002563.pdf

Then you will need to figure out your ststic pressure of the duct system that is connected to the unit.

I have the same model furnace, but the circuit board is dead. My house was hit by lightning while I was out, and various items were fried - e.g.. A couple phones, a stereo receiver. Many things were OK. I have a two of these furnaces and the second one is fine. I get 24.5 VAC from 115VAC to 24.5VAC transformer to the controller circuit board as indicated in the wiring schematic. Also, the car fuse on the board is OK. The LED light on the board does not light up, and no signal is sent to the outside condenser solenoid when I move the thermostat to very cold. In addition, nothing happens when the thermostat is moved to high heat. The other unit does all of this just fine. I am thinking I need to find another board or get this one fixed. There is a processor chip on the board. Best thing I think would be a used board. Any ideas on how to get a used board or where to get my board checked out and fixed?
Thanks.

CFM = Output BTU/hr divided by 1.1 times temperature rise. Temperature rise is determined by starting with a clean air filter and taking the temperature of the supply air and subtracting thr temperature of the return air. This is done in heating mode and supply air temperature should be taken downstream in a trunkline to prevent higher readings caused by heat in the plenum from the "sight" of the heat exchanger. Punch 2 small holes with an awl and use a pocket thermometer. The furnace data plate will spec a temperature rise somewhere between 40-60 degree F.

Example: 74,000 BTU/H divided by 1.1 times 60 (TR) (=66) = 1121 CFM

Also you can try this formula: BTU = CFM times 1.08 times TR (Temp Rise)

Example: 1100 CFM times 1.08 times 60 (TR) = 71,200 BTU/H