Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Operation of Parallel Fan-Powered VAV during cooling

asked 2021-08-08 02:35:33 -0500

Keigo's avatar

updated 2021-08-08 02:37:39 -0500

When complying with ASHRAE 90.1 Appendix G, should we turn off Zone PIU Fan during cooling? Or should we keep it running all the time?

Appendix G specifies VAV with PFP boxes as HVAC system of baseline model for Large nonresidential buildings in climate zone 0 to 3A (hot or warm&humid climate), and it also specifies the airflow of the parallel fan in PFP box. The airflow of the parallel fan is constant.

image description

image description

On the other hand, 90.1-2016 User's Manual shows the following figure and suggests that the parallel fan in PFP box should be turned off during cooling.

image description

I think this Figure 6-V is correct. But if so, since buildinigs in climate zone 0 to 3A has no or less heating mode, the parallel fan is off almost all year round. There is no point in setting airflow and fan power of the parallel fan in accordance with Appendix G. I don't understand why ASHRAE specifies System 6 or System 8 as HVAC systems in hot climate zones.

image description

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted

answered 2021-08-24 03:53:03 -0500

Keigo's avatar

Self-resolved. ANSI/ASHRAE/IES Standard 90.1-2016 Performance Rating Method Reference Manual provides the following explanation.

image description

The Parallel Fan should be off throughout cooling.

From now on, I will refer to the Performance Rating Method Reference Manual first.

edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Training Workshops

Question Tools



Asked: 2021-08-08 02:35:33 -0500

Seen: 455 times

Last updated: Aug 24 '21