Heat Pump Condensate Drains

HEAT PUMP CONDENSATE DRAINS

Most heat pumps have the coil and the condensate drain on the "return" side of the blower. This means that the drain is in a negative-pressure cabinet. Since the drain is in a negative-pressure cabinet, it requires a TRAP in order to properly drain.

DRAIN TRAP

The purpose of the drain trap is to hold water in the drain line so air cannot be sucked through the drain back into the blower. Two reasons:

1. If the drain is sucking-in air, the condensate cannot drain-out until the blower turns off.
2. If the drain is connected to, or near, a sewer drain, the sewer gases can be drawn into the blower and into the space.

COMMON DRAIN PROBLEMS:

1. No Trap
   • The most common issue on a heat pump drain is when no trap is installed.
   • This will typically result in inadequate condensate removal and water around the air handler in the cooling mode.
2. Double Trap
   • A "double trap" is usually the result of a sag or mis-run of the drain line that causes a section that holds water and acts as a second trap.
   • A drain that is double-trapped may not drain at all or may drain slowly or may drain sporadically.
   • To avoid a double trap, it is good practice to install an air vent immediately after the primary trap.
3. Open Cleanout
   • A cleanout is a good idea on a condensate drain, but it must be capped if it is installed between the coil and the trap. Otherwise, air will be drawn in through the clean-out as if there were no trap in the line.
   • The cleanout can be left uncapped if it is installed after the trap. In this case, it will also serve as an air vent to prevent a double-trap situation.