Condensate trap

[AGSelec]

I have not a lot of experience with ducted air conditioners, and i notice some air handling units in roof spaces are not fitted with traps on the condensate drain, I understand you would not put one on the safety pan. I don't fully understand their function on air handling units and what would be the issues encountered with not having one? I work in the humid climate of Queensland.

[redroge]

It depends whether the drain is before the fan or after it ,before the fan air can be drawn up the drain hence the trap after the fan water will drain away hence no trap

[AGSelec]

Thanks for that. Is this likely to cause water issues by drawing air through the drain??

[Keza]

Drain outlet before the fan is negative pressure: needs a trap
As the air is "drawn" over the coil it requires a trap to prevent air and smells entering the conditioned space by being sucked up the drain. Which is prevented by the air lock in the trap.

Drain outlet after the fan is positive pressure: no trap required
This will push any air back down the drain as the fan is running and prevent it coming up the pipe. You can sometimes feel a slight airflow coming from the end of the drain outlet.

Both need to be insulated however to prevent condensation dripping in the roof space.