I apologize! I looked through my reference materials and cannot determine where I got those coefficients, or why I thought they were from ASHRAE 90.1. If I figure it out, Iâ??ll post the information. Otherwise, try the calculation I have attached. It assumes:
· The design delta P varies (shown as 100 ft H2O in the example)
· Pumps normally operate above a minimum speed (shown as 30% in the example)
· They normally maintain a minimum loop pressure setpoint (shown as 8 psig in the example)
James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Adam Barker
Sent: Wednesday, January 08, 2014 4:28 PM
To: 'EnergyPlus_Support@xxxxxxxxxxxxxxx'
Subject: [EnergyPlus_Support] Re: Cubic Curve in variable speed pump
Hi James,
Maybe Iâ??m not looking in the right place, but where exactly in ASHRAE 90.1 do you find these coefficients?
Thanks,
Dear Adrian,
Lacking actual data from the pump and VSD supplier, use the ASHRAE 90.1-recommended coefficients:
E+ Format
90.1 VSD
C1
0.203671
C2
-0.827077
C3
1.181191
C4
0.442055
James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of adrianchong85@xxxxxxxxx
Sent: Wednesday, January 08, 2014 2:46 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Cubic Curve in variable speed pump
Dear EnergyPlus Users,
I'm trying to model a variable speed pump in eplus and one of the inputs required are coefficients to the cubic curve
FractionFullLoadPower =C1 + C2PLR + C3PLR2 + C4PLR3
where PLR = VolFlowRate / NomVolFlowRate
My question is how do we go about obtaining these coefficients? Is it correct to assume a constant head (maybe assume nameplate head) and using nameplate Power and Flow Rate as nominal data, obtain FractionFullLoadPower and PLR by reading off the Pump's performance curves (at different points with the same head) and then use least squares regression to get the coefficients.
Adam Barker, C.E.T., LEED AP BD+C
Sustainability Project Manager
Provident Energy Management Inc.
T: 416-736-0630 x 1874 | abarker@xxxxxxxx
<Pump Power Curve.xlsb>
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