Installer’s Guide
DUCT CONNECTIONS
Air duct systems should be installed in accordance with standards for air conditioning systems, National Fire Protection Association Pamphlet No. 90. They should be sized in accordance with ACCA Manual D or which- ever is applicable.
Central furnaces, when used in connection with cooling units, shall be installed in parallel or on the upstream side of the cooling coil to avoid condensation in the heat exchanger. With a parallel flow arrangement, the damp- ers or other means used to control flow of air shall be adequate to prevent chilled air from entering the fur- nace, and if manually operated, must be equipped with means to prevent operation of either unit unless the damper is in full heat or cool position.
On any job, flexible connections of nonflammable mate- rial may be used for return air and discharge connections to prevent transmission of vibration. Though these units have been specifically designed for quiet, vibration free operation, air ducts can act as sounding boards and could, if poorly installed, amplify the slightest vibration to the annoyance level.
When the furnace is located in a utility room adjacent to the living area, the system should be carefully de- signed with returns to minimize noise transmission through the return air grille. Although these furnaces are designed with large blowers operating at moderate speeds, any blower moving a high volume of air will produce audible noise which could be objectionable when the unit is located very close to a living area. It is often advisable to route the return air ducts under the floor or through the attic. Such design permits the in- stallation of air return remote from the living area (i.e. central hall).
When the furnace is installed so that the supply ducts carry air circulated by the furnace to areas outside the space containing the furnace, the return air shall also be handled by a duct(s) sealed to the furnace and termi- nating outside the space containing the furnace.
RETURN AIR DUCT CONNECTION
NOTE:
On upflow 5 or 6 ton airflow models where the airflow requirement exceeds 1800 CFM - Models will require return air openings and filters on: (1) both sides; or (2) one side and the bottom; or (3) just the bottom.
All return air duct systems should provide for installa- tion of return air filters.
1.Determine the appropriate position to set the furnace in order to connect to the existing supply and return ductwork.
2.For side return installations on upflow models, remove the insulation around the opening in the blower compartment.
NOTE:
Minimum return air temperature is 55° F.
3.The side panels on upflow furnaces include locating notches which may be used as guides for cutting an opening for return air. Refer to Figure 12 and the outline drawing on page 5 for duct connection dimensions for various furnaces.
4.If a 3/4" flange is to be used for attaching the air inlet duct, add to cut where indicated by dashed lines in Figure 12. Cut corners diagonally and bend outward to form flange.
5.If flanges are not required, and a filter frame is installed, cut along knockout guidelines.
6.Upflow Furnaces: Use the optional filter rack on either side or on the bottom if the filter is to be used within the furnace cabinet.
When the upflow furnace is installed in the horizon- tal right or left application and a return duct is attached to the top side as shown in Figure 11, install the filter in a remote location.
Do not install the filter in the return duct directly above the furnace in horizontal applications.
▲! WARNING
Do not install the filter in the return duct directly above the furnace in horizontal applications. Install the filter remotely. Installing the filter directly above the furnace in horizontal applications may cause property damage, serious injury or death.
▲! WARNING
TO PREVENT INJURY OR DEATH DUE TO CONTACT WITH MOVING PARTS, TURN THE POWER TO THE FURNACE OFF BEFORE SERVICING FILTERS.
When the upflow furnace is installed in the horizon- tal right or left application and a close coupled (less than 36") return duct is attached to the bottom side of the furnace as shown in Figure 11, securely attach a 1/2" mesh metal hardware cloth protective screen to the inside bottom of the filter grill to
prevent personal injury from contacting moving parts when reaching into the return opening to replace the filter.
Close coupled (less than 36") return (filter directly beneath bottom side return) is not recommended due to noise considerations.
Downflow Furnaces: Brackets are factory supplied to mount filters in the return air duct work.
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