AZ DEMA – WAATS CMSB – L4525, Marana, AZ
The building is a Mission Critical 24/7 Flight
Simulator Training Facility with three full-motion Simulators
and two supporting Data (Computer) Rooms. The devices provide
flight training to the military of the U.S. and numerous allied
countries. Training, office and conference areas make up the
balance of the facility.
The HVAC system consists of:
- The central plant includes three water chillers with associated
pumps and cooling towers, and is primary-secondary pumped
and piped. The secondary pumps and the cooling tower fans
are all equipped with variable frequency drives.
- There is a hydronic plate/frame heat exchanger to provide
“free” cooling during the appropriate ambient conditions.
- The hot water system is comprised of one boiler and associated
pumps and provides space heating used for Data Rooms’ humidity
control (reheat) and zone heating.
- 4 central station air handling units, one of which is VAV
and serves the VAV boxes in the office/training areas.
- 10 chilled water/hot water computer room a/c (CRAC) units
serving the Data Rooms
- Complete direct digitally controlled EMS.
- Inability to maintain temperature and humidity control in
the Data Rooms
- Central plant was suffering from reverse decoupling due
to original design
- All three 110-ton chillers had 30,000+ hours of operation,
building peaks at 110 tons
- Inability to utilize the existing waterside economizer
- Outrageous (approximately 6 $/s.f./year) utility costs
provided a detailed engineering study and report on the HVAC
System’s current (existing) condition and operation including:
HVAC system design and DDC system deficiencies, potential energy
conservation opportunities with budgeted project costs and economic
analysis, and maintenance related operational and efficiency
analysis. The result of this study became an approximately $500,000
Energy Conservation Project, including Retro-Commissioning and
OptimissioningSM - a combination of HVAC system commissioning
and optimization - of the facility. The project included the
engineering required for the repair, modernization and automation
of the chilled water central plant, the air distribution system,
and the critical Data Rooms’ HVAC components.
The study identified that the central plant
was incorrectly piped and as a result was suffering from “reverse”
decoupling. This condition is actually quite common in primary-secondary
systems, and under various operating conditions elevates the
supply chilled water temperature above what is required. The
elevated water temperatures prevented the Data Rooms from maintaining
temperature and humidity setpoints that were critical to operations.
To compensate, additional chiller systems must be started and
This central plant, intentionally or not, was
equipped with 200% redundant capabilities. The Data Rooms were
equipped with approximately 200% redundancy as well, yet not
even this massive amount of available capacity could overcome
the poor design and lacking EMS practices and setpoints. Naturally,
HVAC related energy costs were extreme as a result. During
the central plant was re-piped to eliminate this reverse decoupling,
and valves were added to allow the secondary pumps alone to
provide the necessary chilled water to the facility during heat
exchanger mode of operation.
An inability to ever use the heat exchanger was cited by one
consultant as a root cause of the excessive utility costs, and
a recommendation to add an additional air-cooled water chiller
dedicated to the CRAC units so as to enable the heat exchanger
to serve the balance of the facility – and thereby save energy
– was provided to the client. Our study and the subsequent
now allows the chilled water system to operate in heat exchanger
mode approximately 4 months of the year, sans any additional
chiller, saving energy and wear and tear on the chiller systems.
The study proposed using the available excess capacity of the
CRAC units to satisfy the Data Rooms cooling needs during heat
exchanger mode, as the warmer than design chilled water temperature
delivered during this mode results in elevated supply air temperatures.
Ambient conditions suitable for heat exchanger operation are
low humidity, making humidity control of the Data Rooms a non-issue
at these times. Iterations of the chilled water coils and load
analysis of the Data Rooms showed that up to 62-degree supply
air temperatures were sufficient to satisfy cooling demands,
so the CRAC’s were equipped with staging (on-off) controls that
enable units to be cycled as needed to meet need, saving significant
energy without affecting temperature/humidity requirements.
The analysis also allowed the chiller-heat exchanger wet-bulb
(WB) temperature changeover setpoint to be established and optimized
for maximum energy efficiency.
All critical EMS setpoints were similarly established and optimized,
and all central plant algorithms were revised. Notably, the
differential pressure setpoint used to control the speed of
the secondary pumps’ variable frequency drives, was eventually
lowered from 12.5 PSI to 4 PSI. A combination of factors enabled
this dramatic reduction, including an engineering innovation
devised to force the CRAC units’ chilled water control valves
closed when the unit was off. This capability did not exist
previously, and manufacturing engineers had stated that it was
impossible to accomplish without a control valve replacement.
To maintain 4 PSI one secondary pump easily satisfies the demand
of the facility. At 12.5 PSI both secondary pumps (one is intentionally
redundant) operated – usually at 60 Hz – in an attempt to meet
the setpoint. All of the electrical loads that were shed as
a result of this OptimissioningSM project, chillers, pumps,
cooling tower fans, and CRAC units, resulted in outstanding
energy savings and corrected all existing deficiencies. The
OptimissioningSM project consisted of the study, the engineering,
the commissioning, the Test & Balance and the optimization
of the facility. Also, project coordination services were provided
by Energy-Environment-Economics in
addition to the HVAC commissioning and optimization services
Results of the project reflected a 70% reduction
in HVAC related energy costs with improved reliability and space
conditions. After commencing in November of 2004 and being released
to full control March of 2005, the project has had an immediate
and staggering impact on energy consumption and utility costs.
Space comfort has improved, including the Data Rooms’ ability
to maintain temperature and humidity within specified limits.
The project has conserved approximately 1.5 million KwH every
year in fully automatic operation. The Kw demand has almost
been cut in ½, from approximately 620 Kw to 350 Kw.
Considering that only the HVAC system was OptimissionedSM, and that lighting
and approximately 400 HP of hydraulic pumping (serving the simulators)
capability was left untouched, these results are nothing short
of spectacular. Due to the concerted efforts of the OptimissioningSM
team, including Mr. Jeff Seaton (Energy Manager, State of AZ.,
NGB), approximately 2/3 of all major HVAC equipment was turned
off, thereby generating these savings, extending the life expectancy
of the existing equipment, and reducing their associated maintenance
requirements and costs. The following charts were created from
actual utility data provided by Mr. Seaton, and generated by
his Utility Manager software:
here to read more.