Trane GEH 006 Manual page 34

Condensate Traps
When designing a condensate trap for the water-source system, it's important to
consider the unit's draw through design.
Under normal conditions, condensate runs down the coil fins and drips into a
condensate pan. In situations where no trap is installed, the water level that
would be maintained in the trap to create a seal, backflows through the drainline
into the unit. Because the fan pulls air through the air-to-refrigerant
heat-exchanger, this incoming air stream could launch water droplets, forming
at the base of the coil, into the air. Air flowing through the coil can then spray
condensate into the fan intake, with the possibility of propelling moisture into
other parts of the mechanical system. This aerosol mist can be carried through
the ducts and into the conditioned air space.
Another problem with air backflow, is the source of that air. Drain lines typically
flow into waste or sewage lines, giving the potential to introduce methane and
other contaminants from the drain system into the airstream.
34
Application
Considerations
In a properly trapped system, when
condensate forms during normal
operation, the water level in the trap rises
until there is a constant outflow. See
Figure 43, for the appropriate
dimensions required in designing a
negative pressure system.
Figure 43: Proper condensate trapping
WSHP-PRC001-EN