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digitalplumber 10-07-2012 01:22 PM

Confused about AC CFM on varying Furnaces
IS there not a standard number, say 400 cfm, per ton for furnace developement for use with AC, per ton?

I ask because I saw this one, but it indicates it is good up to a 5 ton Ac, but only produces 1800 CFM. Seems low for 5 tons to me?

Comments, explanation?

Doc Holliday 10-07-2012 01:53 PM

It'd be like a 5 ton blower on a lower speed setting. Since they don't make a 4.5 ton condenser (in half tons 3.5 is the biggest, then 4 and straight to 5) it's just a selling point that they say it is compatible and while it is it's not the best, correct match up.

You'll never get the full cooling parameters of a 5 ton system.

Doc Holliday 10-07-2012 01:56 PM

Now if used with a heat pump than 350 cfm per ton is the common number so 1750 cfm would be all that's required, that would work with a 5 ton heat pump.

beenthere 10-07-2012 06:37 PM

400CFM per ton is a nominal desired CFM. Many 5 ton systems only have 1600 to 1750 CFM of actual air flow.

I would stay away from the one you posted. Unless your duct system is ideal. The blower in it is rated at a max 1800CFM at a .5" ESP. So if your duct system is under sized like most, you may not even gt 1600 CFM through it. And have your A/C coil freeze up at mild outdoor temps, and a higher electric bill because of the bower motor running at its highest RPM.

digitalplumber 10-07-2012 06:50 PM

Thanks BT, no just looking. That caught my eye because I thought the rule of thumb was 400 square feet per ton.

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