ASHRAE Journal - October 2021 - 64

COLUMN ENGINEER'S NOTEBOOK
FIGURE 7 Filtering the data cloud to project the savings potential associated with eliminating the unnecessary operating hours.
Tons vs. OAT
1,000
800
600
400
200
10
20
30
40
50
60
Outdoor Temperature (°F)
Not an Exact Science
The good news is that the diagnostic model clued us
in to potential ventilation and economizer optimization
opportunities. But by its nature, it could not tell us for
sure which problem existed.
However, it did focus us on the economizer-equipped
systems, where we found that both opportunities existed
(with a unique twist that will have to wait for a future
column for discussion).
Dots Where None Should Exist!
What jumps out the most in Figure 6 is the concentration
of dots in a place you would not expect them.
Dots in the areas outlined in red and yellow (Figure 6b)
are in places where the facility should have been able
to handle the cooling needs using outdoor air. Their
existence points you toward the potential for issues with
economizers (red area) and preheat (yellow area). As we
moved into the project, opportunities were identified in
both areas.
Dots Have Value
The dots represent ton hours. By filtering the spreadsheet,
we can add them up. Figure 7 illustrates what is
revealed by doing that for the ton hours inside the red
outline in Figure 6b.
While broad by design, the projected savings are eye
catching and founded on the physics of the building
and its systems as revealed by trend data and operating
parameters early in the project.
This technique allowed us to firm up savings projections
and budgets initially based on more rudimentary
64
ASHRAE JOURNAL ashrae.o rg O CTO B E R 2021
data and industry metrics.†† We were working with a
director of engineering and crew who had just inherited
the facility. This information focused their efforts to turn
things around, including selling management on what
they needed to succeed.
The Perfect Economizer
A similar technique can be used to model a perfect
economizer. Since the results of our analysis pointed
to economizer and preheat issues, we used it to further
validate the savings we identified.
Conclusion
With a bit of ingenuity and a sense of what should be
going on, EBCx practitioners can leverage data to identify
and quantify operating issues, without being fullfledged
designers/modelers. The information can also
be used to ensure the benefits persist and identify other
opportunities.
Acknowledgments
Thanks to my fellow Engineer's Notebook columnists
for their thoughtful review comments and insights;
Sabastian St. John /St. John Consulting for support in
capturing the data in the example; Jay Tulley and Brian
Clark at CERL and John Hanes at Dewberry for their
support of the perfect load and economizer concepts as
I worked with them on a tool they are developing; Keith
Shockey for sharing his data and his relentless pursuit of
improvements.
††See " Developing Retrocommissioning Implementation Budgets; Establishing the Big Picture " at https://tinyurl.com/BigPictureEBCxSaving
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100
TABLE 1 Potential savings for eliminating false loads.
TOTAL OBSERVED TON HOURS 3,369,098
HIGH END
ITEM
Nominal kW/ton
Nominal Electric Rate
Annual kWh
Annual Cost
False Load Ton Hours
Annual Unnecessary kWh
Annual Unnecessary Cost
LOW END
0.50
$0.0800
1,684,549
$134,764
918,609
459,304
$36,744
0.90
$0.1000
3,032,188
$303,219
(27% of the Total)
826,748
$82,675
Tons

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ASHRAE Journal - October 2021

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