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<DIV>Hi Friends,</DIV>
<DIV> </DIV>
<DIV>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.</DIV>
<DIV> </DIV>
<DIV>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:</DIV>
<DIV> </DIV>
<DIV>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.</DIV>
<DIV> </DIV>
<DIV>Process load: the load on a building resulting from the consumption or
release of process energy.</DIV>
<DIV> </DIV>
<DIV>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.</DIV>
<DIV> </DIV>
<DIV><STRONG>The liberal-interpretation side views it this way:</STRONG></DIV>
<DIV> </DIV>
<DIV>The definition of process load says “consumption or release,” and says
nothing about removing the heat from the space.</DIV>
<DIV> </DIV>
<DIV>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.</DIV>
<DIV> </DIV>
<DIV>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.</DIV>
<DIV> </DIV>
<DIV>Example 2: Following the logic in example 1, a process load's waste heat
that is removed via a chilled water loop rather than an air system should
benefit the bottom line savings through the improved efficiency of the proposed
design's cooling plant over the baseline design. A problem is that there
isn't a way to substitute a DX VAV air system for a chilled water heat
exchanger. Instead, the baseline must include the chilled water cooling
loop. This way, you compare a high-efficiency chiller plant to the
lower-efficiency baseline chiller plant.</DIV>
<DIV> </DIV>
<DIV>The basic argument is that "process energy" is measured at the input energy
source for the process. The total process energy is the sum of the energy
actually consumed by the process and the amount released as waste heat. The
energy consumed is the process energy. The waste heat is the rest.
Therefore, if we add the removal of the waste heat to the process energy, it is
a double dip. We have already accounted for the total process energy at
its input. If we add the energy to get the waste heat out of the building
to the total input energy, we get a number larger than the total energy input to
the process. Once its waste heat is released into the building, it becomes an
element of the cooling load no different from lights, people, envelope, and
others. If not, we are penalized by having to hold constant an amount of
energy that is more than the energy delivered into the building to the process.
The same should apply to a chilled water loop. If a process piece of
equipment is designed for water cooling, it may also have been designed to cool
itself with radiators. In that case, it would be just like the MRI or server
room. Waste heat would become a space cooling load just like any
other.</DIV>
<DIV> </DIV>
<DIV>The liberals also offered up a more complex example, a metal working shop
with welders. The energy that goes into the welders is process
energy. The waste heat is a part of that process. Cooling it away is
a space load, just like the examples above, and is not process energy. But
part of the welder’s input energy is expelled in the form of smoke, the
by-product of the process. If we must also count the cooling energy from
removing the waste heat that is generated by the welding process, should we also
have to count the extra exhaust fan energy and the extra load from the increased
ventilation air that offsets the exhaust? </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV><STRONG>The conservative-interpretation side views it from the polar
opposite position</STRONG>. 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.</DIV>
<DIV> </DIV>
<DIV>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.</DIV>
<DIV> </DIV>
<DIV>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.</DIV>
<DIV> </DIV>
<DIV>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.
</DIV>
<DIV> </DIV>
<DIV>Dave</DIV>
<DIV> </DIV>
<DIV>David R. Weigel, PE</DIV>
<DIV>Managing Member</DIV>
<DIV>1189 Golden Circle SW, Lilburn GA 30047</DIV>
<DIV>678-353-6941 office 901-619-1716
cell</DIV>
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