Hello all,
I am working on an energy model for a warehouse in Dallas, TX. The design intent of the warehouse area required 1 air change per hour during the summer. The fans are suppose to operate simultaneously as makeup units that serve the warehouse. Therefore, 10 make up air units and 10 supply fans serve the warehouse area to meet this air change requirement. Modeling the makeup air units can be done by eQuest but I am curious how I should incorporate the supplement supply fans?
Thanks!
William Mak
A follow up question to this, has anyone been successful in controlling the max CFM out of a unit with seasonal schedules. For example, a system can produce 15000 CFM during the winter but 30000 CFM during the summer? This would help me with the modeling of these supplemental supply fans that serve the warehouse space as they only operate during the summer. My strategy would be to schedule this extra CFM during the summer, though I am still trying to figure out how to properly model the actual energy usage since the fan power from the make up units differ from the supply fans...
William Mak
Will,
I'm not sure how you are setting up your supplemental supply fans. You
could try using a minimum flow schedule at the zone level to vary the
flow of the system supply fan. If you are trying to model exhaust fans,
you could also apply an exhaust fan schedule at the zone level. If the
supplemental fans are for circulation only (not supply or exhaust, but
just blowing air around), then model them as a process load.
Regards,
Bill
William Bishop, PE, BEMP, LEED(r) AP
Bill,
Thanks for the feedback.
I am attempting to model the fans by adding the additional CFM to the makeup air unit systems. I am trying to use a schedule to modulate the total CFM available during different times of the year (hence my previous question about this before). The more I am thinking about this though, the more I believe that it's not the correct method to model the fans. The makeup air units and the supply fans have different fan powers associated with them. By adding the CFM to the makeup air units, I am associating the wrong fan power and generating the wrong energy usage from the fans.
I tried using the minimum flow schedule strategy at the zone level to vary the flow of the system supply fan. However, it only controls the minimum a space can supply, not the max which is what I'm trying to control.
These fans are called "supply fans" because they bringing in extra air to meet the minimum air change requirements during summer operation months called out in the specs. They bringing in a 100% OA as they are hooded roof type fans. The make up air units are interlocked with these fans and both operate at the same time. The warehouse area is a heating only condition. Therefore, during the summer, there is no conditioning on the air brought in by the make up units and supply fans. Could the fans be modeled as a process load with these criteria?
Appreciate all the help!
William Mak
Will,
It sounds like this is unconditioned outside air, so I think a zonal
exhaust fan is what you want. If the exhaust source is "infiltration",
which it probably is, create an exhaust fan schedule that matches the
makeup air unit schedule during the summer and is off during the winter.
Bill