How to replace an air conditioning condensate pump with a safety overflow switch.
While many central air conditioning units use a sloped PVC line running into a floor drain or sump pit some units use a condensate pump to collect water in a reservoir and then pump it to a drain in another location. Condensate pumps are useful when you have a unit located inside a living space or an attic, or when there is not a drain nearby.
On new units there is a built-in safety switch that will shut off power to the air conditioner if the pump is full. This prevents the AC unit from producing more condensate are causing water damage. You can tell if you have this type of pump it you see 2 wires connected to the pump along with the 120V power cord.
Usually condensate pumps fail due to sludge build up on the inside that prevents the pump from coming on or the debris causes the safety switch to malfunction. Most manufacturers recommend cleaning the condensate pump each time the filters are changed, but cleaning the internal parts of the condensate pump 2 or 3 times during the cooling season should be sufficient.
Corroded Condensate Pump
If you find that your pump is not running, but you need to keep the AC unit running you can do the following:
1. Remove the old pump. Unplug the pump and disconnect the control wires and twist them together and replace the wire nut.
2. Try to run the hose or pipe to the lowest point possible. If there is piping installed, you may have to remove it and replace it with a hose. You may also cut the pipe about 3 or 4 inches from the unit and slide a hose over it and hold it in place with a hose clamp. (Since the pipe is probably ¾-inch PVC you may have to use a shop vac hose.)
3. Run the hose into a bucket and check it often. An air conditioning unit can remove several gallons of condensate a day.
You can also disassemble the pump and empty it into a sink or outside. This way you can leave the piping and wiring intact.
Related Air Conditioning Repair articles:
How to Fix Frozen Air Conditioning Coils
How to Replace an Air Conditioning Condenser Fan Motor and Blade
Replacing Condensate Pump
Most home centers stock condensate removal pumps, but you may have one with higher horsepower or lift than is commonly available. Lift is how high the pump can lift the water, this is important if you have to pump the condensate long distances and over a wall. You can go online to research you existing pump to see if is still made. You may have to locate an HVAC distributor in your area to find the correct pump. United Refrigeration Inc. has branches in 44 states and Canada; www.uri.com
The replacement is fairly simple as the wiring and piping are all in place. The repair should take about 10 to 15 minutes. If you had to cut the existing condensate line you can repair it with a PVC coupling and PVC cement or a rubber coupling with hose clamps.
Hacksaw, if you need to cut PVC pipe to remove the old pump
PVC Coupling or Rubber Repair Coupling (Sometimes referred to as a Fernco coupling)
Typical Condensate Pump Installation
Note: Make sure you set the pump on a level surface or mount it on a wall so that it is completely level.
Removing the Existing Pump
Your existing condensate pump may have several lines coming into the reservoir; such as the condensate line from the air conditioner, a drain line from a humidifier, and a condensate line from a high efficiency boiler.
1. Turn off the AC/heater system at the thermostat.
2. Disconnect the power cord to the pump.
3. Remove the wire nuts that connect the AC/heater safety shutoff wires to the float switch. This circuit is either 12 or 24 volts.
4. Remove the flexible discharge tube from the barbed nipple on the condensate pump.
5. Remove cover on the old pump and slide the reservoir out and remove the PVC pipe.
6. Use a pipe brush to clean out the inside of the condensate line with a little bleach and water.
7. Set the new pump in place.
8. Reconnect the drain and discharge lines.
9. Connect the safety shutoff switch wires from the pump to the air handling unit. Follow the instructions that come with your pump.
10. Plug in the pump and turn the thermostat to cooling mode.
11. Fill the pump basin with water and test.
Note: If your condensate discharge line is going through warm, unconditioned spaces, like an attic, you may want to install some foam insulation over the tubing to prevent condensation from forming. The condensation can drip from the line and cause water stains on ceiling, damage insulation, or promote mold growth.
Cleaning a Condensate Pump
• Turn off the AC unit.
• Unplug the condensate pump power cord.
• Remove the cover from the condensate pump.
• Wash the reservoir with hot water.
• Wash the submerged parts of the pump with warm water and a soft scrub brush or old toothbrush.
• Reinstall the cover on the reservoir, plug in the pump and turn on the AC unit.
To keep the condensate drain pan in the air handler clean, consider adding some condensate tablets to the pan to eliminate any sludge or slime.