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gotoman for ac
gotoman for ac, HVAC Technician
Category: HVAC
Satisfied Customers: 5206
Experience:  51 years of experience install design and repair of all makes and models of AC
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I have a two story house, i am gonna install a 3 ton unit on

Customer Question

I have a two story house, i am gonna install a 3 ton unit on 1st floor 1200 sqft. I am using the existing 6 inch round metal duct for 8 of them. The cfm on high of the blower fan is 1625 cfm. Is it too much cfm for those 8 of the 6 inch metal duct?
Submitted: 2 years ago.
Category: HVAC
Expert:  gotoman for ac replied 2 years ago.
6 inch duct will handle approx. 125 cfm. So 1625 is too much for those ducts. They will handle it but will be very noisy. The 3 ton unit CFM should be no more than 1200 cf.. 400 cfm per ton. Russ
Customer: replied 2 years ago.
Should i use 2.5ton unit then? Which has 1250 cfm on high of the blower fan. But 2.5ton. X400= 1000cfm, so for 1200sqft is not enough
Customer: replied 2 years ago.
So maybe the data sheet i saw of 1625 cfm might mean rpm on the blower motor
Customer: replied 2 years ago.
So maybe the data sheet i saw of 1625 cfm might mean rpm on the blower motor.
Expert:  gotoman for ac replied 2 years ago.
Depending on air handler some are capable of that cfm with variable speed air handler. I would go with 3 ton and just drop fan speed on motor. Russ
Customer: replied 2 years ago.
If i drop the fan speed to medium on cooling, will that be a problem for not enough air flow thur the coil and ice up the evaporator?
Expert:  gotoman for ac replied 2 years ago.
NO you will not have a problem. You can lower fan speed to 370 per ton and it will be fine. To much air flow and the coil does not pick up moisture. Russ