Free Cooling problem

[DelphineO]

Hello,
I am a new user of Vitual Environment 6.4.0.5 and I've been trying to put a free cooling system that would bring outside air during the night to cool naturally a building located in Marocco. I've just add a free-cooling capacity of 5Ac/h in the Building Template Manager Window - System Tab . In the tabular room data, i can see that this capacity is also written, I have an "On continiously" schedule for the outside airflow.

But I've got a weird free cooling vent graph : See the graph image at this adress (I don't know how to attach a image here) https://docs.google.com/open?id=0B8i9m7 ... l80TFJpYTQ
Between 2 AM and 6 AM , I have a low outside airflow and I don't understand why, because the outside temperature is low, and can contribute to cool the building before the day.

Is there any tutorial about free cooling ( I'm not using Apache HVAC), I would like to use only ApacheSystem. Where can we add a high-limit shutoff temperature ?
What are the parameters that are important for the freecooling airflow? Is there a link between the Plant schedule and the freecooling (or other schedule ?)
Thank you for your help. I am a bit lost with this...

[DelphineO]

Ok I found the answer, which was maybee obvious for some of you.
Actually the free cooling depend of the cooling setpoint temperature and the cooling plant schedule. So in my case i have to decrease my Cooling Temperature during the night to optimize the free cooling !