ASHRAE Journal - December 2020 - 33

TECHNICAL FEATURE

air to the " recommended " or at least to the " allowable "
range.
Ongoing commissioning is even more critical under
emergency situations. One example was the deadly 2018
" Camp Fire " in Butte County, Calif. The NERSC facility
experienced high air pollution and had to completely
shut off outdoor air for an extended period. This scenario was not anticipated during design and triggered a
series of control issues. The facility used only AHU cooling coils with tower-cooled water as the cooling source
since direct evaporative cooling creates a rapid indoor
humidity increase. 100% return air operation lasted for
two weeks, and seven building management system
(BMS) logic ﬂaws surfaced and were ﬁxed.4
It also led to condensation on a cooling water manifold
in the underﬂoor plenum, triggering a water leak alarm.
Condensation was considered extremely unlikely during
design because the facility is normally tightly coupled
to outdoor wet-bulb temperatures. However, this event
proved condensation can be an issue if 100% return air
persists long enough. This event resulted in new air pollution control sequences,4 which have improved facility
resilience during the increasingly active annual wildﬁre
seasons in California.
One key NERSC energy efﬁciency team's success is a
deep recognition of the need for commissioning building operations in an ongoing rather than one-off manner. They've adopted a continuous improvement cycle
approach (Figure 4)-trial and error with data validation
being an important part. The team meets regularly,
led by the chief sustainability ofﬁcer, to follow up on
implementation/testing progress and obstacles. It also

FIGURE 4 Continuous improvement cycle used for NERSC's ongoing-commissioning.

Identify
Opportunities

Tweak As Needed
Until Satisﬁed

Verify Using
Trend Data

Deﬁne Critical
Control Boundaries

Try It Out!

allows the team members to identify connections with
other efforts and serve as advocates for commissioning projects in their interactions with other teams. The
team's focus has evolved over time, which is illustrated
in Figure 5 with approximate timelines. Some of the high
impact efforts were:
* Submetering** and PUE Tracking: A detailed assessment identiﬁed where additional submeters were
necessary based on impact. One challenge was that the
existing circuit breaker trip units were not accurate on
light loads.
* Air Management:†† One challenge was the exhaust
air duct's location relative to cold aisles,‡‡ which was addressed by improved containment.
* Cooling System Projects: One example is adding a
second heat exchanger and installing a booster pump
for the ofﬁces comfort-cooling loop to lower pumping

FIGURE 5 Timeline of NERSC's key energy management achievements.

Add 2nd HX, Valve Control
Reduce Pressure Drop
Install Submeters
For Accurate PUE
Relocated to Wang Hall
From Oakland

2015
**Submetering

Install Booster Pump
Reduce Cooling Pump Power
Tower Water Temp. Reset
Use Approach Temp.

OMNI Operational Data
Operation Decisions

Over-Voltage Event
Shunted HPC Panels

Energy Audit
Identiﬁed 1 GWh/Yr Savings

2016

2017

Response to Wildﬁres
Fixed Control Flaws
15-Minute PUE
Decision: No New Substation
Available
Saved $2 Million
Rigorous
Advanced
OCx Analysis Ready
Calculation
BMS Data Incorporated

Air Management
Containment, Exhaust

Arc Flash
Prioritized Shutdown

2018

HPC Dynamic Fan Control
Reduce Fan Power

2019

Future

involves using power meters to measure electricity use at a level below the utility meter.

††The

practice of effectively separating the airstream on the cold, intake side and the hot, exhaust side of IT equipment. The intent is to
minimize cold supply air bypassing to the exhaust side and also reduce hot exhaust air recirculating back to the intake side.
D ECEM BER 2020

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ASHRAE Journal - December 2020

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