Fan:ComponentModel Duct Static Pressure Reset Example File???

asked 2019-10-15 19:00:26 -0600

mldichter
2575 ●2 ●11

I'm trying to use the "Duct Static Pressure Reset Curve Name" field of the Fan:ComponentModel object to have the VAV dampers open more at lower flow rates allowing the fan to run at a lower pressure and power, thereby saving energy. However, I can't seem to get the "Duct Static Pressure Reset Curve" to influence the simulation, even when changing the curve value by a factor of 10 in either direction.

I suspect I'm not interpreting the curve correctly, or do not have an appropriate paired object. Is there an example file for a non-constant "Duct Static Pressure Reset Curve" available? The ExampleFiles-ObjectsLink.html only lists files with a constant "Duct Static Pressure Reset Curve" called DiagnosticSPR

Curve:Linear,
    DiagnosticSPR,           !- Name
    248.84,                  !- Coefficient1 Constant
    0.,                      !- Coefficient2 x
    0.,                      !- Minimum Value of x
    100.,                    !- Maximum Value of x
    62.5,                    !- Minimum Curve Output
    248.84;                  !- Maximum Curve Output

Is there another way to get my VAV dampers to open more and lower the fan pressure and power? There's a lot of room for improvement in my file as the VAV are usually 30% open at the lowest flow rate with the pressure mostly constant at 534 across the fan.

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answered 2019-10-23 13:44:47 -0600

mldichter
2575 ●2 ●11

updated 2019-10-23 13:46:21 -0600

The "Fan Pressure Rise Curve" must be modified in tandem with the "Duct Static Pressure Reset Curve" in the Fan:ComponentModel object in order to open the VAV dampers more and run the fan at a lower pressure, thereby consuming less energy.

The "Duct Static Pressure Reset Curve" takes as input flow the m3/s flowing through the ducts and outputs the desired duct pressure at that flow.

The "Fan Pressure Rise Curve" takes as input the flow and "Duct Static Pressure Reset Curve" output. The four terms in the "Fan Pressure Rise Curve" represent different sources of resistance in a duct system model including, but not limited to, the return duct resistance, supply duct resistance, damper resistance, and the weight of the duct static pressure in fan operation. For a much more accurate and detailed explanation, see the Engineering Reference.

If you implement the two curves correctly, you will see a change in damper position, flow, pressure across the fan, and fan energy use in the simulation.

There is still no example file as of this writing, so do your best to estimate the coefficients in the two curves.