In EnergyPlus is it possible to do hybrid sizing for ventilation in some zones and total load in other zones? The scenario I'm thinking is where you have a hybrid VAV and active chilled beam (ACB) design where some of the VAV boxes are sized solely for ventilation as in a DOAS set-up and others are sized for load.
I don't think it is possible to completely autosize the central air handler properly for this scenario because sizing on VentilationRequirement affects the entire system. But this is possible to model with manual sizes. I would do two autosize runs before hand, one for ventilation and the other for total load, and then use those results to help determine the hybrid air handler sizes in a side calculation. Then enter all the design sizes as "hard" values in the IDF so as to not mix autosize and manual sizes in the same file.
I thought this was the case. Would you happen to know if there is development to set sizing at the terminal units that relay the sizing information back to the air handler as opposed to the sizing:system being either some form of load or ventilation, but not a hybrid?
I am not aware of any efforts underway to do this in general. But I should have pointed out that there is one hybrid configuration that is supported -- if the all the zone load sized terminals are the new four pipe beam and all the terminals for ventilation are of a different type, then VentilationRequirment will work for hybrid size. The new four pipe beam has a unique sizing method that finds a primary flow somewhere between ventilation and total load and updates the central air handler size accordingly.
I've added it as a feature request here. I'm sure there is going to be a reason as to why this is difficult to implement, but I think the added flexibility in putting the responsibility of determining what load to size for on the terminal units would be a great feature to have.
Asked: 2015-12-14 20:02:37 -0500
Seen: 375 times
Last updated: Dec 15 '15
