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. Check on controls to make certain they are correct for the electrical supply.
Central furnaces, when used in connection with cooling units, shall be installed in parallel or on the upstream side of the cooling units to avoid condensation in the heating element, unless the furnace has been specifi- cally approved for downstream installation. With a par- allel flow arrangement, the dampers or other means used to control flow of air shall be adequate to prevent chilled air from entering the furnace, and if manually operated, must be equipped with means to prevent op- eration of either unit unless the damper is in full heat or cool position.
On any job, flexible connections of nonflammable ma- terial may be used for return air and discharge con- nections 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, am- plify 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 which minimize noise transmission through the return air grille. Although these winter air conditioners are designed with large blowers operating at moderate speeds, any blower moving a high volume of air will produce audible noise which could be objec- tionable 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 per- mits the installation of air return remote from the liv- ing 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.
Minimum return air “entering temperature” for the furnace is 55° F.
Where there is no complete return duct system, the re- turn connection must be run full size from the furnace to a location outside the utility room, basement, attic, or crawl space.
DO NOT install return air through the back of the furnace cabinet.
RETURN AIR DUCT CONNECTION
NOTE:
On upflow 5 or 6 ton airflow models, if the airflow re- quirement exceeds 1800 CFM, these models will re- quire return air openings and filters on both sides; OR 1 side and the bottom; OR just the bottom.
All return air duct systems should provide for installa- tion of return air filters.
PREPARATION FOR UPFLOW BOTTOM AND SIDE RETURN AIR FILTER INSTALLATION
All return air duct systems should provide for installa- tion of return air filters.
1.Determine the appropriate postion to set the furnace in order to connect to the supply and return ductwork.
2.The return air filter and rack are shipped in either the bottom or side location. Remove the filter and filter rack by first turning the two latches on the blower door and tilting the door forward to remove. Remove the filter by sliding it out of the rack. Compress the spring loaded filter rack to disengage the retaining pins/screws from the furnace sides and slide the filter rack out.
The filter rails are spring loaded for automatic adjustment to allow standard size, locally obtainable replacement filters. The filter rack itself slides to adjust to the required width needed for bottom or side return.
3.For upflow side return installations, remove the insulation around the opening in the blower compart- ment.
▲! 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.
4.The side panels of the upflow furnace include locating notches that are 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.
5.If a 3/4" flange is to be used for attaching the air in- let duct, add to cut where indicated by solid lines in Figure 12. Cut corners diagonally and bend out- ward to form flange.
6.If flanges are not required, and a filter frame is in- stalled, cut between the locating notches. See Figure 12.
7.Upflow Furnaces: a filter rack is factory supplied for bottom or side return. Use the filter rack on ei- ther side or on the bottom if the filter is to be used within the furnace cabinet.
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