Shouldn’t there be a trap on this setup, before the vertical vent. This set up is blowing conditioned air out the vent.
From what I see in the picture, yes a trap should be installed. As far as they system blowing conditioned air into the space, I don’t see how that would be possible. The condensate pan is below the evaporator coils which are below the blower. I could see the possibility of it sucking air through the blowout in the picture, but not blowing air out. If it really is blowing air out, I would check the rotation of of the blower motor and it’s orientation.
Just read another thread and completely forgot about blow through set-ups. I don’t run across any where I’m at because most HVAC contractors install draw through systems from what I see around here. If it is a blow through system, then yes you definately need a trap and there neds to be a cap on that blow-out fitting.
Thanks Scott… 
I wish furnace and heat pump manufacturers put installation documents on the web like other appliances do (water heater,etc…). You know, something to refer to…
This pages may help.
They used to be on the Trane site, but have disappeared.
I retrieved them form the Wayback Machine Net Archives, and combined them into a single document:
Great, thanks for the pdf, that is exactly what I was looking for.