100% OA Air Handling Unit

asked 2020-09-25 11:23:44 -0500

Carlos Kelly's avatar

updated 2020-10-01 09:18:36 -0500

Hello everyone

I'm trying to model a 100% OA AHU system, the system is actually pretty close to a classic baseline Sys8. Consists on Reheat VAV terminals, a main AHU, water cooled chiller and cooling tower. I've already tried to hardsized the OA flow to match the design cooling supply air but somehow the system only supplies the minimum OA defined by the standard.

Any ideas?

Btw. I'm running OS 3.0.1 and everytime I try to load the BCL browser, it completely crashes the entire OS and shuts it down. Anybody else with this problem?

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I think if you hard sized the OA that means the DOAS is capable of providing that capacity of OA, but since there is no demand for this amount the system will deliver the minimum OA. I think increasing the OA defined by the standard to match the design flow rate would solve the problem.

Saif's avatar Saif  ( 2020-09-29 09:16:35 -0500 )edit

Yes, I actually ended up doing this however I'm aware is not a proper approach. Since, when hardsizing the OA to be the same as my supply, it didn't increased my coil capacity nor cooling energy consumption, just fans. It just doesn't make sense that a 100% OA system consumes the same cooling energy that a system with ASHRAE ventilaiton rates. Still tryna work around a better approach but for the moment this one was ok.

Carlos Kelly's avatar Carlos Kelly  ( 2020-09-29 09:38:57 -0500 )edit