Temperature and points below setpoint

[ksga]

I think I am missing something completely here.
Trying to get the PID to control the setpoint of an AHU (running it's own PID which I have no way of controlling).
Supply air is affected by the temperature in the attic even though the ductwork is well insulated...

For now I'm just letting the PID work on the supply air temperature supplied from the AHU to see how it reacts to changing setpoints and input.

I think I have something completely wrong in my setup. Even though supply air temperature is below the PID setpoint, the output is below the setpoint - and of course that would never work.
I have the min/max set to the AHU limits...
A few screenshots:


Any obvious mistakes?