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Operation of Parallel Fan-Powered VAV during cooling

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

Keigo gravatar image

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.

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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.

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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.

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

Keigo gravatar image

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

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The Parallel Fan should be off throughout cooling.

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

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

Seen: 304 times

Last updated: Aug 24