SECTION 9. INSTALLING DUCT SYSTEM
Properly size duct system based on heat loss and heat gain calculations to ensure good heating and cooling installations, potentially fewer
CAUTION: Failure to follow these standards could reduce airflow or increase air leakage, resulting in reduced system performance or furnace damage.
Design duct system so furnace will operate at a static pressure of 0.50 inches W.C. or less. This static pressure limitation includes the total pressure losses on both supply air side and return air side of system. Supply side pressure loss includes cooling coil, ducts and room registers. Return side pressure loss includes retu rn grilles and ducts. Pressure losses are calculated based on 400 CFM per ton of cooling.
SUPPLY AIR DUCT WORK
Supply air duct (plenum) connections must be at least as big as furnace supply opening. Seal
On furnaces not equipped with a cooling coil, a removable access panel that is large enough to allow viewing of the heat exchanger should be provided in the supply duct. The access panel should be accessible when the furnace is installed. Seal
RETURN AIR DUCT WORK
When furnace is installed so that supply air ducts carry air to areas outside the space containing the furnace, returnair must be handled by a duct(s) sealed to furnace casing and terminating outside the space containing furnace.
WARNING: Failure to seal
Air delivery above 1800 CFM requires that both sides of furnace be used for return air, or a combination of one side and bottom or bottom only.
If bottom return air is not used, you must attach a solid
Table 5. Bottom Closure Part Numbers.
| GAS | MOTOR* |
| BOTTOM CLOSURE |
INPUT* | HORSE- |
| PART NUMBER |
(Btu/hr) | POWER |
|
|
54,000 | 1/3 |
| 4045901 |
72,000 | 1/2 | 4045901 | |
90,000 |
|
|
|
72,000 | 3/4 | 4045902 | |
90,000 |
|
|
|
108,000 | 3/4 | 4045903 | |
126,000 |
|
|
|
*GAS INPUT and MOTOR HP can be found on furnace rating plate.
WARNING: Failure to install bottom closure panel could allow combustion products to enter circulating air
stream, resulting in injury or death by asphyxiation.
DUCT DAMPERS
You may balance airflow with dampers installed in each branch run duct and adjust for even temperature throughout the heated space. For proper furnace operation, make sure of the following:
??Supply air registers and return air grilles are open;
??Rugs, carpets, drapes or furniture are clear of registers and grilles;
??Size and shape of supply air plenum is correct;
??Number of supply air ducts is correct.
LOCATION OF COOLING COIL
If furnace will share common duct system with a separate cooling unit, install furnace parallel to or upstream of cooling unit. This avoids condensation in heating element. Do not install cooling coil in
SECTION 10. SELECTING AND INSTALLING FILTER CABINETS
Properly installed air filters keep blower motor, blower wheel and cooling coil (if installed) clean. Filters and filter cabinets are not supplied with this furnace. Filters and filter cabinets must be field supplied or obtained from the manufacturer. The manufacturer has bottom and side filter cabinets available. This furnace was designed for an external filter(s). Do not install air filters inside furnace casing. Obtain and install proper filter frames and correctly sized filters. To inspect, clean or replace air filters, follow the instructions in the User’s Information Manual.
CAUTION: You must install air filters to keep blower motor, blower wheel and cooling coil (if installed) clean. Dirty equipment may reduce system efficiency or cause erratic control performance and can result in damage to blower motor, heat exchanger or air conditioner (if installed).
Page 18 | Installer’s Information Manual |