AC Sizing

A 4 ton AC is nominally 48,000 Btu/h of cooling capacity, but delivered cooling depends on conditions, airflow and installation.

Cooling design temperature is a local sizing condition, not the hottest temperature the city has ever reached.

At 400 CFM per ton, 2,000 CFM corresponds to about 5 nominal tons; at 350 CFM per ton it corresponds to about 5.7 nominal tons.

Manual J inputs should be checked before replacement so the new AC is selected for the house as it exists now.

A common residential target is about 350 to 450 CFM per ton, with 400 CFM per ton used as a frequent starting point rather than a law.

Cooling load is what the house needs removed; cooling capacity is what the equipment can remove under rated conditions.

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