Ironbug - Supply and Return Plenum

Grasshopper Plugin
1

Hello there,

I am trying to create a plenum that is used as return plenum from one zone and as a supply plenum for another zone. I have created two airloops and two seperate plenum objects. I have assigned the same plenum zone as a return and supply plenum respectively.

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I am not sure if this is a limitation of Ironbug/ OpenStudio, but when I look at the HVAC system in OpenStudio I see that in the first loop (as they are connected to my HVACSystem) the plenum zone is assigned correctly.
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But in the return side there are random plenums assigned with no zone attached to them.
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If I reverse the order of the airloops then the plenum zone is assigned correctly to the return loop but not the supply loop. I tried a few things like adding all zones in the same airloop instead of two seperate but with no luck. Any ideas?

3

It would seem that Energy Plus does not allow the same zone being assigned as plenum in seperate loops. My solution is to split the plenum into two subzones, each used for one of the loops, and then connect them with an Air Boundary. This requires me to enable AFN.

However, if I add an exhaust fan as equipment to the zones using the supply plenum, the AFN does not work and I get the following:

** Severe ** AirflowNetwork::Solver::validate_exhaust_fan_input: Fan:ZoneExhaust is not defined in AirflowNetwork:MultiZone:Component:ZoneExhaustFan

4

@mingbo, do you know what might be going on here?