How to Install a Forced Hot Air Heat & AC System

Furnace

• 1

  Place the furnace in a central location in the basement or utility room on top of a 4-inch high concrete pad.

• 2

  Run ducts for the cold air return ducts. Run rectangular ducts to other area of the cold air for the return. Cut an opening in the floor or wall and install a cold air return grill.

• 3

  Assemble the plenum and connect it to the furnace with screws. The plenum consists of a galvanized metal box that holds treated air as it is distributed to different parts of the home.

• 4

  Cut a hole in the supply plenum and attach a takeoff. Run rectangular duct work from the takeoff to create an extended plenum to service the largest area. Cut the holes in the extended plenum for starting collars. Install round pipe on the collars to branch off to the different rooms.

• 5

  Place support straps about every 6 to 10 feet. Attach a register boot at the end of the duct and connect to a floor or wall register. Secure all joints with sheet metal screws and wrap with foil metal duct tape.

• 6

  Run PVC vent pipe from the combustion/exhaust inlet on the top of the unit to the exterior wall of the roof. Use long sweeping elbows to avoid sharp bends and to keep the flow as straight as possible. Cut the PVC pipe with a hacksaw. Clean grease, dirt and burrs with a cloth.

• 7

  Spread PVC primer around the edge of the pipe. Apply a coating of PVC cement on the edge of the pipe and insert it in the fitting. Slope the pipe 1/4 inch per length of pipe run to where it exits to the outside.

• 8

  Run the gas line from the meter to the furnace. Consult the installation manual and local codes for pipe diameter and other specifications. Install a gas shut-off valve near the furnace and provide supports as required by local building codes.

• 9

  Perform a pressure test on the gas line at 30 pounds per square inch for 15 minutes or in accordance with local requirements.

Air Conditioner

• 10

  Measure the evaporator coil for the supply plenum opening. Mark the measurement on the supply plenum. Cut the rectangular opening with aviation snips.

• 11

  Screw the evaporator shelves, which come with the AC kit, into place inside the plenum. Follow the manufacturer’s instructions for installing the evaporator.

• 12

  Install the condensing unit on the exterior concrete pad. Cut an opening in the wall with a 2-inch hole saw mounted on the drill.

• 13

  Lay the 3/8-inch and 3.4 -inch tubing from the condenser to the evaporator coil. Follow the local and national codes for connecting the tubing and charging the refrigerant system.

Electrical

• 14

  Shut the power down at the main electrical panel before staring the electrical work. Touch a voltage tester to wires before getting started.

• 15

  Run the electrical wiring and components for the HVAC system. Follow the product manufacturer’s installation guides and electrical code for the installation of disconnect switches near the furnace and condenser.

• 16

  Install a heating and cooling thermostat inside the living space about 5 feet off the floor. Avoid installing the unit in a drafty area or in direct sunlight. Run low-voltage wiring. from the furnace controls to the thermostat.