All installations and services must be performed by qualified service personnel.
17
DUCT WORK/AIR CONDITIONING:
If the furnace is used in connection with summer air conditioning (cooling), the furnace should be installed parallel
with or on the upstream side of the evaporator coil to avoid condensation in the furnace heat exchanger. If the
cooling unit is installed with a parallel flow arrangement, dampers or other means used to control flow of air should
be provided to prevent chilled air from entering the furnace. If such a damper is manually operated, it must be
equipped with a means to prevent operation of either unit, unless the damper is in the full heat or cool position.
The duct system should again follow the design standard of Air Conditioning Contractors of America (ACCA) or
ASHRAE. (Latest Edition Fundamentals Volume).
A slab coil (HE style) is available for the horizontal air flow application on the PGT5-11-16 furnaces. (See Fig.
below).
To obtain proper CFM with air conditioning installed on a belt drive unit, the motor and/or blower pulley may need
to be changed. On a direct drive unit the blower motor speed may need to be changed depending upon the size of the
air conditioning system installed and the static resistance of the duct system.
NOTE:
The horizontal units have direct drive blowers and no pulley or motor change is required. See direct drive
motor and blower specifications for air conditioning CFM's at .5 static.
SIZING THE DUCT WORK FOR A COMBINATION HEATING AND COOLING SYSTEM:
Two formulas must be used in determining the CFM requirements of a combustion heating and cooling system.
1. HEATING CFM:
BTU'S OUTPUT OF FURNACE
1.1 X TR (TEMPERATURE RISE) =
HEATING CFM
EXAMPLES:
A. 110,000 BTU OUTPUT
1.1 X 850F TR = 1176 CFM FOR HEATING
B. 110,000 BTU OUTPUT
1.1 X 700F TR = 1429 CFM FOR HEATING
2. COOLING CFM: 400 CFM X COOLING TONNAGE (12,000 BTU PER TON) =
CFM FOR COOLING
EXAMPLES:
Summary of Contents for PGL20-180
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