Air Terminal:Dual Duct:VAV:Outdoor Air overrides maximum allowed branch flow

asked 2015-10-30 02:46:27 -0500

Pantamonium's avatar

updated 2015-10-30 10:13:23 -0500

Hello all,

I am trying to model a demand controlled system for a space where the occupants frequently surpass the original design numbers.

I am using the Air Terminal:Dual Duct:VAV:Outdoor Air component in CurrentOccupancy mode and a Design Outdoor Air Specification with a Flow/Person value. The problem is that despite any limits I have set on the air loop's maximum outdoor air flow, including a maximum flow limit on the dedicated outside air branch (which is supposed to supercede any other branch component's max allowed flow), the terminal keeps increasing its outdoor air supply to account for the extra occupants.

What I'm trying to do is have the terminal add the outdoor l/p/s value for each extra person up to the system outdoor air limit and then keep providing this amount even if more people come in. Instead, the terminal increases its outdoor air flow without any regards to the system limit.

Any suggestions on what I'm doing wrong?

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What do you have set for your Maximium Outdoor Air Flow Rate in your Controller:OutdoorAir object?

Neal Kruis's avatar Neal Kruis  ( 2015-10-30 10:12:49 -0500 )edit

@Pantamonium, congratulations! You now have the coolest handle on UnmetHours, pushing @pflaumingo to second place.

__AmirRoth__'s avatar __AmirRoth__  ( 2015-10-30 10:33:34 -0500 )edit

Well it turns out I had left the maximum air flow of my Fan:VariableVolume to autosize and limiting this did the trick. But the question still remains about why the flow was surpassing the maximum allowed branch flow. From the EnergyPlus documentation it is implied that a flow limit on a branch takes precedence over every other component limits.

Anyway I am sorry for waisting space with my question. Next time I'll try not to miss anything before asking.

@Neal Kruis I have set a specific value that was being surpassed.

@__AmirRoth__ Haha, both are animal inspired I see!

Pantamonium's avatar Pantamonium  ( 2015-10-30 23:58:02 -0500 )edit