First time here? Check our help page!
3

In OpenStudio, where does one enter the "minimum fan power ratio" for variable volume fans?

I am looking to model some older fans using the performance curves outlined in the ANSI/ASHRAE/IES Standard 90.1-2010 Performance Rating Method Reference Manual on page 164, and I can not figure out how to define the minimum fan power ratio.

Thank you in advance.

willyJohan's avatar
1.5k
willyJohan
asked 2016-11-10 15:46:47 -0500
David Goldwasser's avatar
20.4k
David Goldwasser
updated 2016-11-11 09:52:22 -0500
edit flag offensive 0 remove flag close merge delete

Comments

add a comment see more comments

1 Answer

2

I think you'd do this:

In the Fan:VariableVolume:

  • Set Fan Power Minimum Flow Rate Input Method to "Fraction"

  • Set Fan Power Minimum Flow Fraction to the % flow rate that corresponds to the minimum % power listed for that curve. See table and figure below. An important highlight from the documentation for this field:

    Note that this field is only used to calculate the fan power. This field does not enforce the system air flow rate during simulation.

    This means that although the fan power will be correct, the actual flow rate that goes through the ducts and terminals into the zones will not.

  • I suspect that the way to set the actual flow rate minimum limit is to edit the Minimum System Air Flow Ratio field in the Sizing:System object attached to the AirLoopHVAC with this fan, but I have not tested this.

image description

Note: For the Multi Zone VAV with AF or BI with Inlet Vanes curve, there is no minimum flow that corresponds to the published minimum % power. I'd probably go with 0.5, but this is something to ask the PNNL authors about.

aparker's avatar
8.2k
aparker
answered 2016-11-11 16:32:23 -0500
edit flag offensive 0 remove flag delete link

Comments

add a comment see more comments