From inside (document excerpt):
Condensing Heat Exchanger Kit Cancels: IIK 399A-40-1 IIK 399A-40-4 2-15-92 Installation Instructions Part No. 312731-751 through -754 NOTE: Read the entire instruction before starting the installation. INTRODUCTION This instruction covers installation of a polypropylene-laminated (PPL) steel condensing heat exchanger and collector box assembly kit in a downflow condensing furnace. See Table 1 for furnace and kit combinations.
NOTE: If this kit is used to replace a stainless steel condensing heat exchanger in a Model 399A, Series A, or a 58DX, Series 100 Furnace some modifications to the vent system or unit may be necessary. Refer to Step 6–Replacement of a Stainless Steel Condensing Heat Exchanger with a PPL Condensing Heat Exchanger. NOTE: Obtain a releasing agent (Pam or equivalent) and RTV sealant (G.E. 122, 162, or Dow-Corning 738) before starting the installation. SAFETY CONSIDERATIONS Installation and service of heating equipment can be hazardous due to gas and electrical components. Only trained personnel should install or service heating equipment. Untrained personnel can perform basic maintenance functions such as cleaning coils, or cleaning and replacing filters. All other operations should be performed by trained service personnel. When working on heating equipment, observe precautions in literature, and on tags and labels attached to the unit. Follow all safety codes. Wear safety glasses and work gloves. Have a fire extinguisher available. Step 1–Removal of Inducer Assembly 1. Turn OFF gas and electrical supplies to furnace. 2. Remove blower and control access doors. 3. Disconnect electrical connector from inducer control box (if used) and disconnect wires from pressure switch. 4. Disconnect inducer motor leads. 5. Loosen hose clamp and remove drain tube from bottom of inducer housing. 6. Loosen hose clamp, at pressure switch, on pressure tube from plastic tee. Remove tube from pressure switch. 7. Loosen hose clamp, at collector box, on tube from pressure switch. Remove tube from collector box. 8. Loosen hose clamp, at collector box, on drain tube from inducer outlet elbow. Remove tube from collector box. 9. Remove 2 screws securing vent enclosure and remove enclosure. 10. Loosen hose clamp at vent pipe connection; disconnect vent pipe. Position pipe out of way. 11. Remove and discard mounting screws securing inducer assembly (motor, pressure switch, inducer housing, mounting bracket, and inducer outlet elbow). Remove inducer assembly from furnace. 12. Remove inducer controller (if used) on left side of casing. Step 2–Removal of Condensing Heat Exchanger and Collector Box Assembly 1. Loosen hose clamp on 7/8-in. OD drain tube at collector box; remove tube. Before beginning any installation or modification, be sure the main electrical disconnect switch is in the OFF position. Electrical shock can cause personal injury or death. DESCRIPTION AND USAGE This kit contains the following items: Condensing heat exchanger assembly (includes collector box) Transfer tube outlet gasket Stainless steel screws (in bag) Limit shield (in 312731-754 kit only) Installation Instructions (1) (1) (max 16) (1) (1)