[EnergyPlus_Support] RE: Question about how to set 90.1 baseline pump in Energyplus

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	η

Watts =	746	x	DeltaP
GPM	3962		η

	Assuming η =	0.78

Watts =	746	x	DeltaP
GPM	3962		0.78

=	0.2414	x	DeltaP



Therefore, if desired W / GPM = 'x' (and η = 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
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.

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

____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses

__._,_.___

Primary EnergyPlus support is found at: http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx The primary EnergyPlus web site is found at: http://www.energyplus.gov The group web site is: http://groups.yahoo.com/group/EnergyPlus_Support/ Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files. EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.

Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe

__,_._,___