To replace an air handler on a heat pump, locate the connection of the air handler to the ductwork, disconnect the power to the heat pump, and install the new handler. The heat pump is a metal box containing the heater elements, a blower, dampers and filter chambers.
Unfasten the flanges that connect the air handler to the ductwork, and remove the line set connections that connect the air handler to the heat pump. Detach the drain connections. Remove the control wiring that connects to the thermostat.
Once all the connections are removed, place the old air handler aside, and start installing the new handler. Make sure the new air handler has the same dimensions as the old one to ensure easy fitting.
Place the air handler into position, and connect it to the ductwork using the two flanges on the metal box. Ensure the handler is leveled and stable. Reconnect the drain connections. The drain connection drains the condensation created by the air handler unit when it is cooling.
Make the line connections from the air handler onto the heat pump. Strip a portion of all the wires that connect to the thermostat. Loosen the screws on the thermostat terminals, push in the wires, and then tighten the bolts. Finally, connect the high-voltage electrical connections to power on the unit, and turn it on.