I have been attempting to successfully use eQuest for the past year or
so and am finding it to be an excruciatingly frustrating experience. It
is definitely a "quirky" program.
My latest confusion has to do with the difference between the LS-A, SS-A
and SS-D reports. The documentation indicates that you need to go to
SS-A to results that account for time varying air temperatures. SS-A
reports are not described in the Detailed Simulation Reports Summary,
nor anywhere else that I can find.
LS-A Space Peak Loads reports:
Cooling peak = 35.070 KBTU/hr; Heating Peak = -20.826 KBTU/hr.
SS-A System Loads Summary reports: (not included in Detailed Simulation
Reports Summary documentation)
Cooling maximum = 2.684 KBTU/hr; Heating Maximum = -4.275 KBTU/hr
SS-D Building HVAC Load Summary reports: (not included in Detailed
Simulation Reports Summary documentation)
Cooling maximum = 24.81 KBTU/hr; Heating maximum = -28.14 KBTU/hr
I am wondering what these results could possibly mean. The order of
magnitude difference between the LS-A and SS-A reports baffles me. I
MIGHT be able to understand it for cooling if the SS-A results were ten
times as high, but I don't understand how the heating could be double.
These values don't seem to make sense, but since there is no description
of the reports there is no way to tell.
The SS-D report seems to make some sort of sense in relation to the LS-A
report if the LS-A report is giving "instantaneous" results as if the
building were at a steady state condition and the SS-D report includes
the impacts of thermal mass and things like that. However, since there
is no documentation on this I am must guessing.
I am of course being interested in sizing a heating and cooling system
for the building. Given these different and unexplained differences in
the reports I am finding that to be difficult to do.
Can anyone explain what these reports are telling me and how I might
best use them as part of the design process? Right now I just have to
pick one that "feels" good - but that isn't a very satisfying approach.
Thanks
LS-A is for the space or whole building depending on which cooling load
value you are looking at, without the systems. LS-D is for the whole
building. SS-D is for all the systems together. SS-A is for a particular
system. SS-D will include the outdoor air, and the thermostat setting you
are using. If you have only one system in the building, SS-D and SS-A will
be same.
eQUEST is based on the DOE2 simulation engine. DOE2 starts by calculating the building heating and cooling loads. These loads are calculated assuming a constant space temperature. Once the loads are calculated, DOE2 moves on to calculating the system response to meet the loads. At this point, adjustments are made to account for the actual space temperatures. In addition, the load from conditioning incoming outdoor air is also calculated. Finally, DOE2 calculates the plant response required to serve the heating/cooling needs of the systems.
LS-A shows the peak loads in each space and the time of the peak for each space. Note that the times of the peak can be different for each space. If you want the whole building, look at the LS-C report.
SS-A shows the load by month for a single system.
SS-D shows the peak load for the whole building.
Note that the sum of the SS-A peaks will not necessarily equal the peak load for the whole building as the peak loads for individual systems may be happening at different times.
Hope that helps,
Dan
?
Daniel Knapp, PhD, PPhys, LEED? AP O+M
danielk at arborus.ca
Arborus Consulting
Energy Strategies for the Built Environment
www.arborus.ca
76 Chamberlain Avenue
Ottawa, ON, K1S 1V9
Phone: (613) 234-7178 ext. 113
Fax: (613) 234-0740
>From the Detailed Simulation Reports Summary (a searchable .pdf accessible
from the Help->Tutorials and References menu):
Keep in mind, LOADS reports LS- do not include outdoor air for ventilation -
that is added at the SYSTEM level.