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[EnergyPlus_Support] Re: Question about how to set 90.1 baseline pump in Energyplus
Jim,
Slightly sidetracking from Jenny's question but... ASHRAE 90.1-2004 User's Manual says that 22 W/gpm corresponds to a 75 ft head with a 60% motor and impeller efficiency. Using the same equation as you (which I'm usually using), I get a 70.1 ft head.
The User's Manual also says that 19 W/gpm translated to a 60 ft head with a 60% combined efficiency.
75/22 = 3.41
60/19 = 3.16
Their relationship between head and power/flow (at constant efficiency) does not seem to be linear. Any idea how they calculated that?
Thanks,
Patrick
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Jim Dirkes <jim@...> wrote:
>
> Jenny,
> Your question #2:
> I think E+ follows much the same logic as you describe for eQuest. It is also easy to test by using different values of motor efficiency to find the resulting power.
> The method below shows a derivation for US (IP) units of the necessary pump pressure rise to satisfy ASHRAE 90.1. You will notice in the very last line that it assumes 100% motor efficiency. This is not the case for any motor, but you can easily adjust the formulae for the actual motor efficiency.
>
>
>
> Pump Power (90.1 Limitation)
>
> US measure:
>
> Watts =
>
> GPM x
>
> DeltaP x
>
> 746
>
>
> 3962 x
>
> ç
>
>
> Watts =
>
> 746
>
> x
>
> DeltaP
>
> GPM
>
> 3962
>
> ç
>
>
>
> Assuming ç =
>
> 0.78
>
>
> Watts =
>
> 746
>
> x
>
> DeltaP
>
> GPM
>
> 3962
>
> 0.78
>
>
> =
>
> 0.2414
>
> x
>
> DeltaP
>
>
>
>
> Therefore, if desired W / GPM = 'x' (and ç = 0.78 x 1.00)
>
> - Chilled water; ASHRAE 90.1 baseline
>
> DeltaP =
>
> 22
>
> =
>
> 91.1
>
> ft. H2O
>
>
> 0.2414
>
>
> =
>
> 272,420
>
> Pa (Use this for ASHRAE 90.1 Baseline)
>
>
> Similarly, for Heating and condenser pumps
>
> DeltaP =
>
> 19
>
> =
>
> 78.7
>
> ft. H2O
>
>
> 0.2414
>
>
> =
>
> 235,270
>
> Pa (Use this for ASHRAE 90.1 Baseline)
>
>
> Note:
>
> E+ assumes a pump mechanical efficiency of 0.78. For this derivation to remain correct, use a motor efficiency of 1.00
>
>
>
>
> 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 Jenny Zhang
> Sent: Saturday, May 04, 2013 5:46 AM
> To: 'EnergyPlus_Support@xxxxxxxxxxxxxxx'
> Subject: [EnergyPlus_Support] Question about how to set 90.1 baseline pump in Energyplus
>
>
> Hi All friends
> I have questions about how to set 90.1 baseline pumps in E+
>
>
> 1) The condense water pumps
>
> 90.1 G3.1.3.11 states that Each chiller shall be modeled with separate condenser water and chilled-water pumps interlocked to operate with the associated chiller.
>
> For chilled water pumps it is easy to solved, because we could set CHW pumps in each chiller chilled water branch and of course the chilled water pump will run only the chiller run; but for condenser water pumps I face the problem that I could put cw pumps in chiller condenser water-side branch.
>
> Does E+ requires condenser water pumps to be put only on the condenser water branch?
>
> I think there is two way to do the setting: (1) set headed pumps in the cw supply side branch or (2) set more than one cw tower(same as chiller nos) and for each cw tower put a condenser water pump in the branch.
>
> Which is better? Or Do you have other method?
>
>
>
> 2) Pump power
>
> 90.1requries pump power for chilled water/hot water/condenser water pumps. How to set it? In eQuest usually I use pump head & total efficiency to ensure the power/flow rate(such as 75ft&65% =22W/gpm),
>
> But in E+ I find it difficult to do the same setting. Only motor efficiency can be input, and how about pump efficiency? Is it 78%, I find in the EngineeringReference.pdf "The motor efficiency is an input. Since we need the total efficiency to calculate the nominal power consumption we assume an impeller efficiency of 0,78 for purposes of sizing". Does it means that the total efficiency is motor efficiency* 0.78 or we can use "Fraction of motor inefficiencies to fluid stream" to control the total efficiency? I really confused.
>
>
> [cid:image001.png@...]
>
> Many thanks!
>
>
> Best Regards
>
> Jenny Zhang
> Assistant Engineer | Building Sustainability
>
> Arup
> 39/F-41/F Huaihai Plaza 1045 Huaihai Road (M), Shanghai 200031, China
> t +86 21 3118 8888 d +86 21 3118 8750
> f +86 21 3118 8882
> www.arup.com<http://www.arup.com/>
>
>
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