[Equest-users] Another process load question
ncaton at smithboucher.com
Mon Oct 22 16:25:41 PDT 2012
I’ve often intentionally differentiated space conditioning equipment for spaces housing significant process loads between my baseline/proposed models without incident from the LEED reviewership, per your example #1. Commonly occurring scenarios include server rooms and elevator machine rooms with small mini-split DX cooling.
I’ll maintain, this is something that can and should remain open for interpretation by the modeler – not one mold will fit every project. There may be cases where modeling consumptions/loads and the corresponding space conditioning discretely is overly complex or disadvantageous, in which case holding everything constant between the models would be an acceptable approach. A self-contained walk-in freezer with its condenser at the exterior comes to mind as something I probably wouldn’t break apart (but either interpretation could work).
Whatever you choose, I wouldn’t flip-flop too much on the issue within the same project. Try to take a unified interpretation and apply that to both baseline and proposed for each space/case – it will make documentation for EAp2 spreadsheets easier later.
[cid:489575314 at 22072009-0ABB]
NICK CATON, P.E.
Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of The Watt Doctors - Dave Weigel
Sent: Saturday, October 20, 2012 6:32 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Another process load question
This is more of a LEED / ASHRAE 90.1 question, but I see a lot of experience in this group. I hope someone has some experience with a LEED review on this issue. It may be a moot point, but I can’t go into the arguments below without a little backup.
A debate has arisen among engineers, architects, and a LEED AP regarding the cooling energy for space conditioning in an area with process loads. This is specifically related to 90.1-2007 exception G3.1.1.b, and to a literal vs. extended interpretation of 90.1-2007 part 3.2, definitions:
Process energy : energy consumed in support of a manufacturing, industrial, or commercial process [implying medical equipment as well] other than conditioning spaces and maintaining comfort and amenities for the occupants of the building.
Process load: the load on a building resulting from the consumption or release of process energy.
This may be a moot point if it has already been the subject of a LEED 2009 CIR, or if there is an official ASHRAE interpretation or addendum. I haven’t been able to find any of those.
The liberal-interpretation side views it this way:
The definition of process load says “consumption or release,” and says nothing about removing the heat from the space.
Process energy is the total input energy to a process. The additional energy to cool the space in which the process resides is not process energy, it is a building space conditioning load.
Example 1: A server room, MRI room, or a room full of autoclaves is allowed to have system 3 (packaged DX VAV) in the baseline model under this exception rather than system 7 (chilled water VAV). While the process load itself must be simulated the same in baseline and proposed design cases, energy savings from the higher efficiency of the space cooling system is included in the bottom line savings. This includes the cooling load imparted to the space by the process load, such as the waste heat from the autoclaves, MRI, or servers.
The conservative-interpretation side views it from the polar opposite position. They contend that all input process energy plus the energy required to remove its waste heat must be held constant, no matter if the cooling is done by a building air system or by the building chilled water plant.
For the definition of process energy, “energy consumed in support of manufacturing, industrial, or commercial process,” they claim that the energy to remove waste heat is “in support of” the process and must be counted as process load.
In eQuest terms, the conservative side says we must extract the hourly cooling loads that are due to each and every piece of waste heat from process equipment. Then we re-insert that cooling load profile as process energy and hold it constant from the baseline to the proposed design as an external load on the meter. So, the MRI process load turns into the input power plus the energy to cool it.
I'm not saying which side I'm on. I would not be a big fan of extracting and manipulating all those load profiles, especially in the case of that welder.
David R. Weigel, PE
1189 Golden Circle SW, Lilburn GA 30047
678-353-6941 office 901-619-1716 cell
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