After unpacking and assembling the air filter, separate the plenum from rest of the air conditioning system, set the air handler over the plenum and seal the ducts with mastic and butyl or fiberglass tape, advises SF Gate. Ideally, air handlers should be installed on a temperate day.
Before installing an air handler, the gas and electricity powering a heating, ventilation and air conditioning system should be turned off, warns SF Gate. The furnace is then separated from the plenum, the part through which conditioned air gets to the ducts. The location of the plenum varies by house type. After unpacking and assembling the air filter and associated hardware, it is set over the plenum and the ducts sealed in accordance with manufacturer instructions.
If the blower is also being replaced, it should be bolted to the blower shelf in the air handler; the bolts should be tightened properly to avoid rattling, advises SF Gate. Once that is done, the furnace is attached to the air handler. For an ideal fit, the air handler and the furnace should be from the same manufacturer.
Once the insulated tube that shunts fluid to the exterior condenser and the copper line that channels compressed fluid to the evaporator coils are attached, the blower fan connected to the furnace control and the drip line connected, the internal filters that are part of the air handler kit are connected to the racks near the evaporator coil, explains SF Gate.