Hello David,
Your pump is probably operating at a different point since you've defined a new boundary condition by using the D2A. If you search in our online knowledgebase, you will find some information on this message:
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In HAMMER, the efficiency for a pump during the initial conditions must be between 30 and 95%.
The efficiency is different depending on the operating point of the pump. Go to Components > Pump definitions, click your pump definition and look at the plotted efficiency for each operating point. In the properties of the pump element in question, look at the pump head and flow and compare that operating point with the pump curve to see what the efficiency is. The calculations behind HAMMER assume that a pump’s nominal operating point (gotten from the initial conditions) is at or close to the best efficiency point, which is why you get that message.
If the pump in question is off in the initial conditions and you want to have it start up, make sure you choose “pump startup” as the transient pump type, then enter the nominal head/flow. (corresponding to a good efficiency from the pump definition)
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If you're using a variable speed pump battery (VSPB) with multiple efficiency points, this entry may help:
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This may be due to a known issue with version HAMMER V8i SelectSeries 3 (build 08.11.03.16). It has been reported in earlier builds as well. Please use one of the following workarounds:
1) Enter the constant efficiency for the VSPB instead of using the Best Efficiency Point. To find the constant efficiency, run the initial conditions of the model. Next, right-click on the VSPB and select "Pump Curve". Verify that both Head and Efficiency are checked under "Curve Choices" and select Okay. Note the efficiency value for the curve. Now, go to Analysis > Pump Definition. Select the Efficiency tab and choose "Constant Efficiency". Enter the value from the pump curve as the constant efficiency. Leave the Motor efficiency as is. The user notification refers to Total Efficiency, which is a combination of the pump efficiency and the motor efficiency.
2) Remove the VSPB and replace it with the equivalent number of individual, parallel pump nodes, configured the same way.
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If this doesn't help, you may need to send the model to technical support. Also, I would caution the use of the discharge to atmosphere (D2A) unless it really is a free discharge. If you really do have a siphon with sub-vapor pressure conditions, the D2A approach would not be an accurate reflection of the real system conditions.