The condensate that a furnace’s evaporator coil makes is collected and taken away by a condensate pump. The drain line of the furnace dumps condensate into the pan of the condensate pump. Once a certain amount of condensate is in the holding pan, the pump’s float switch turns on the pump motor.
The pump motor pulls the condensate out of the holding pan and forces it into a drain line. The discharge drain line either sends the condensate to a drainpipe that drains by gravity or to the outside of the building.
A new furnace condensate pump replacement will use the same drain lines and electrical connections as the old one.
How to Connect a Condensation Pump to a Furnace
Furnaces produce condensation as part of their normal functioning. If this condensation is not removed from the furnace, it can extinguish its pilot light and cause other problems. Normally, furnaces are installed above a condensate drain, and the condensation is simply diverted into the drain. However, when this is not possible, a condensate pump can be a useful means for eliminating condensation from the furnace and directing it into the condensate drain.
- Place the condensate pump in an ideal location. The pump must be close to the furnace itself and close enough to the condensate drain to minimize the tubing needed to connect the two. Place the pump close enough to an electrical outlet that the pump’s power cord can easily reach the outlet.
- Connect the condensate outlet on your furnace to the inlets on your condensate pump. Some models of condensate pumps feature several inlets for convenience; simply choose the one with the least amount of PVC or flexible tubing.
- Connect discharge tubing from the condensate pump outlet to the desired condensate drain. Use plastic tubing unless advised to use another material by the manufacturer’s instructions.
How to Wire a Furnace Condensate Pump
- Turn OFF the circuit breaker.
- Examine the condensate pump’s wiring chart. The chart identifies the high- and low-voltage wires. If the condensate pump has an “NC” and a “NO” low-voltage option, choose the “NC” low-voltage position.
- Run the condensate pump’s low-voltage wires into the air handler’s electrical connection box. The condensate pump’s low-voltage wire set contains two thin wires, usually 18-gauge wire.
- Remove the wire nut holding the thermostat’s red wire to one of the transformer’s low-voltage wires and separate the two wires. The transformer has two low-voltage wires: one connects to the ground lug, and the other sends power to the thermostat.
- Twist one of the condensate pump’s low-voltage wires to the thermostat’s red wire. Twist the second condensate pump low-voltage wire to the transformer’s low-voltage wire. Twist a wire nut over each pair of wires.
- Connect the condensate pump’s high-voltage wires. If the condensate pump model has a high-voltage cord with a plug, then insert the plug into a wall receptacle. If the condensate pumps hard wires into a high-voltage power source, run the condensate pump’s high-voltage wire into the air handler’s electrical box and connect one high-voltage wire to the ground lug the other wire to one lug on the air handler’s terminal block. The wires from the circuit breaker enter the air handler and connect to the air handler’s high-voltage wires at the terminal block.
Every make and model of condensate pump has its own distinct installation instructions. You should always follow those instructions in the first instance to ensure proper furnace condensate pump installation or replacement. Also, comply with all local building and safety codes regarding where to properly ventilate the furnace condensation.