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Re: [EnergyPlus_Support] ASHRAE Pump modeling approach





Hello Javed.

I came across with the same question. I looked up in the internet but  seems that there is not an answer for your question in the standard ASHRAE. Some people told me that they have sent LEED projects with 22W/gpm for each loop and haven´t got any comments from the reviewer but you never know.

Regards  


From: Javed Iqbal <eee.javed@xxxxxxxxx>
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Tuesday, 18 September 2012, 7:01
Subject: [EnergyPlus_Support] ASHRAE Pump modeling approach

 
Hello,
I'm confused on how to interpret CHW pumps for App. G.  Specifically, item 7 and 8 and how the 22 W/gpm is defined for a primary secondary configuration.  Section G3.1.3.10  can be interpreted (at least) two different ways.

First, Section G3.1.3.10 Chilled-Water Pumps (Systems 7 and 8)
â??The baseline design pump power shall be 22 W/gpm.  Chilled-water systems with a cooling capacity of 300 tons or more shall be modeled as primary/secondary systems with variable-speed drives on the secondary pumping loop.  Chilled-water pumps in systems serving less than 300 tons cooling capacity shall be modeled as primary/secondary systems with secondary pump riding the pump curve.â??

The question:
Should each primary and secondary pump be sized for 22 W/gpm OR should this â??design pump powerâ?? be divided up (in some way) between the primary and secondary pumps?

Possibility A:
If the 22 W/gpm should be the TOTAL pumping power, there is no guidance on how to divvy up this requirement and the constant volume primary pumps could be sized for 20 W/gpm and the secondary (VSD or riding pump curve) can be allotted 2 W/gpm.  


Possibility B:
Sizing each primary pump and secondary pump to 22 W/gpm will over-estimate the baseline pump energy (VSD or riding pump curve) and this is not the intent of 90.1. How do you interpret (and model) 90.1 App. G chilled-water pump power requirement of 22 W/gpm? p.s. I'm clear on what parameters needs to be changed in order to get 22W/GPM but i'm curious in knowing the modeling approach. Should i consider it as Complete system approach OR individual loop/pump approach?

Thanks,

--


Javed Iqbal, LEED AP, CEA
Energy Analyst 




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