One FCU serving multiply zones, and with an outdoor air MAU

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Hello all: I am trying to model an FCU serving three small offices in a whole building using OpenStudio. My aim is to simulate the room temperature for every office and check if it matched the actual temperature, so I define every office as a single zone. Furthermore, there is an AHU serving the whole building, so it serves outdoor air for the three offices ( every office has one diffuser). The FCU and AHU both use heating/cooling coil.

Because the zone equipment "Four pipe fan coil" only serves a single zone, so I use AirLoopHVAC Unitary System and a fan to simulate the FCU, connect it into the three thermal zones with diffusers. but I've no idea how to add outdoor air in this case.

Another way is that I model an AHU with outdoor air serving the three thermal zone, then add zone equipment "Four pipe fan coil" for all zones. This method means I have three FCUs for every office, not one FCU serving three offices, which is different from the actual situation.

I was wondering if you have any comment in this case, and any answer is welcome! Thanks.