PTAC should add DOAS?

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Dear all

I am doing LEED-CS energy rating simulation. Part of the project is
residential type and the HVAC system for baseline is PTAC and the proposed
system is FCU+DOAs. However the PTAC system has no outdoor air and the
energy consumption of PTAC without DOAs in baseline is less than the
proposed building. So I think the PTAC system should add DOAs.

Has anyone performed the PTAC system simulation and agree with my opinion?

Look forward to reply! Thank you very much!

Zhiren Zhou

zhiren zhou's picture
Joined: 2011-09-30
Reputation: 0

Why does the PTAC not have any outdoor air? Each PTAC should have
outside air - usually you want that rate to either be the ASHRAE 62.1
requirements, or match the proposed (there has been a lot of contention
about which, so I'd play it safe and use the ASHRAE 62.1 values). You
don't want to add DOAS to the baseline PTACs, as that is not how
Appendix G tells you to create the baseline system. Just assign OA to
each PTAC.

James Hansen, PE, LEED AP

James Hansen's picture
Joined: 2011-09-30
Reputation: 200