Forum discussion
NC-2009 EAp2: Minimum Energy Performance
Based on ASHRAE 90.1, the chilled water pumping power must be 22 W/gpm and does not mention the effect of pumps' head. the majority of projects that I am working on them, the proposed pumping power is higher than 22 W/gpm because of the pumps' head.
How can I solve this issue or how can I design the baseline chilled water pumps based on flow and head?
LEEDuser is supported by our premium members, not by advertisers.
Go premium forTo post a comment, you need to register for a LEEDuser Basic membership (free) or login to your existing profile.
A portion of our building envelope is historic. Can we exclude it from our model?
For an existing building, do I need to rotate the model?
Our process load is higher than 25%. Do we have to justify that?
Our local code references ASHRAE 90.1-2010. Should I use that for my documentation, or 90.1-2007?
Can mezzanines open to floors below be excluded from the energy model?
How do I provide a zip code for an international location?
For a project outside the U.S., how do I determine the climate zone?
For a project outside the U.S., how do I determine the Target Finder score?
Do hotel rooms need automatic light shut-off control?
How commonly are the 90.1 mandatory compliance forms submitted as part of EAp2/EAc1?
The Section 9 space-by-space method does not include residential space types. What should I use?
Can the Passive House Planning Package (PHPP) be used to energy model for LEED?
Which baseline HVAC system do I use if my building has no heating or air conditioning?
Our project has a diesel backup generator. Should we include it in our energy model?
Can SHGC be higher in the proposed than in the baseline model?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
February 9, 2017 - 11:24 am
The baseline must be 22 W/gpm of collective chilled water pump power (both primary and secondary). The loop is auto-sized which determines the gpm needed.
I can't really say how to solve the pump issue in your designs that produces greater power demands than the baseline. It is unusual that you would have this issue because most projects show a savings against the baseline.
Ahmed Labeeb
UAEP&T Architects
1 thumbs up
February 10, 2017 - 7:08 am
Based on ASHRAE 2004 User Manual, the baseline pumping power is calculated based on a pumping head = 75 foot and efficiency = 60%.
Consequently, Should I redesign the proposed pumping power based on head = 75 ft and Eff = 60% and the only difference will be the chilled water flow to make the comparison apples to apples.
Ahmed Labeeb
UAEP&T Architects
1 thumbs up
February 10, 2017 - 7:12 am
Based on ASHRAE 2004 User Manual, the baseline pumping power is calculated based on a pumping head = 75 foot and efficiency = 60%.
Consequently, Should I redesign the proposed pumping power based on head = 75 ft and Eff = 60% and the only difference will be the chilled water flow to make the comparison apples to apples.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
February 10, 2017 - 11:20 am
No. The Proposed must be modeled as designed and the Baseline loop is auto-sized.
Aru Sau
5 thumbs up
February 10, 2017 - 1:50 pm
Correct me if I am wrong - I would convert the 75' head to pressure and calculate the gpm of the proposed system. I.e. if you have 1000 gpm, 100' head & 40 hp pump. For the sake of LEED proposed, I would put calculated w/gpm value considering it on 75' head. That way it could be apple to apple not apple to orange.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
February 10, 2017 - 2:22 pm
The proposed loop would be modeled as designed. The proposed pump is sized based on the head and the flow needed to serve the coiling coils in the Proposed design.
The 75' head is what was used to come up with the 22W/gpm in the baseline, it is not a value you should use in the models at all. The baseline pump size would be determined by auto-sizing the loop and using the required W/gpm. This will provide you with the necessary flow to serve the coils to meet the load.
It seems as if you are trying to design the baseline system which is a common tendency for mechanical designers. It is not designed. In some cases as it is modeled would not actually function in reality. It must function in the computer simulation, not in real life.
In many cases you don't want this to be apples to apples because the system configuration can vary and this should be taken into account.