Thermo Products PGL37-312, PGT16-160, PGT5-100, PGL20-180, PGT11-125, PGL39-400, PGL33-250 service manual

All installations and services must be performed by qualified service personnel.

EXAMPLE: Heating output of furnace is 100,000 x 1.4 ÷ 100 = 1400 CFM. Air conditioning installed is 4 tons x

400 CFM = 1600 CFM or 48,000 BTU's. NOTE: The duct system must be sized for the larger CFM requirement for cooling. If only 3 tons 36,000 BTU's of cooling x 400 CFM = 1200 CFM was installed, the duct would have to be sized for the 1400 CFM heating requirement.

To insure obtaining the necessary air handling capacity of a duct system, each of the system components (trunk lines, take offs, runs and register and grill-free areas) must be properly sized and matched together. A 12"x8" duct with a 400 CFM capacity for example will not flow 400 CFM if the register(s) to which it connects only flow a total of 200 CFM.

To achieve proper air movement, the main trunk lines, take offs, registers and grills of the supply return air duct system must have an adequate square inch area to move the desired CFM. The chart shows the CFM air-handling capability based on a 0.1" SP loss, in the supply duct system.

DUCT SIZES FOR HOMES, QUIET OFFICES OR SIMILAR INSTALLATIONS

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