Yes, this variable speed approach is a good solution.
The plant routines inside EnergyPlus have recently been completely reworked and now it is very likely that branch pumps on demand side are fully supported. (The same general solver is now used for both the demand side and supply side.) This and other expanded flexibility is not yet claimed in the documentation because more detailed testing is needed. As long as you are careful and check the results, it should be okay to push the model in this way.
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of ecoeficientees
Sent: Sunday, June 17, 2012 4:02 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Solution to constant branch pumps, when bypass is not possible
I am using a configuration for branch pumps when in the real HVAC system they are constant flow pumps with bypass (through three-way valves).
I use variable speed pumps, setting the curve performance coefficients (1,0,0,0), so power consumption is constant although it can deliver variable flow.
I think it is a good solution to account for a constant pump with bypass, since it provides variable flow but constant power. It is the only way I have found to account for constant pumps as branch pumps, since bypass is not possible.
Do you see it right?
It seems to work ok even with branch pumps in demand side, which should not work according to E+ Reference but Energyplus is not complaining.
That's my second doubt, are branch pumps in demand side correct? As I've said, E+ seems to simulate them right, but Engineering Reference says that pumps in demand side can only be used in the first branch. Why is not Energyplus launching an error, then?
Regards,
Germán Campos.
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