Matt - Is the refrigeration equipment modeled? Or is it just assumed as a process load? If it is just an assumed process load, then you will need to know the amount of recoverable heat (and a schedule). Let's say it is 10 MBH: Then, you would have to create a heating plant for the makeup air. That heating plant would contain at least two pieces of equipment, the first being the "recovered heat". Set the capacity to 10 Mbh (in this case), and then you set the rate to something like .001 KW. Finally, set your schedule for that equipment if it is not running 24/7. Then you would have "free" heat up to 10 mbh for that makeup air plant, the remainder of which would come from the next piece of equipment. Anyway, we might be able to come up with something better, but we'd need to know more about the particular setup. Bob Fassbender Energy-models.com On Wed, Mar 21, 2012 at 3:37 PM, wrote: