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TECHNOLOGY AWARD

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Civic Center Retrofit

he Long Beach (Calif.) Civic Cen-ter was built in 1973 and consistsof City Hall and the Main Library.City Hall is a 14-story buildingwith a single basement level that

houses city agencies, the city council anda 350-seat council chamber.

The library is a two-level structurewith a park built over the upper level wallsand roof. The lower level of the library is

About the Authors

Cynthia A. Callaway, P.E., is a lead senior designengineer at Southland Industries, Long Beach, Calif.She is a a Regional Vice Chair for Region X of ASHRAE.

Kevin L. Davis, P.E., is the automation engineeringmanager at Southland Industries.

Janie Kuehn is a senior design engineer at SouthlandIndustries.

Lanty K. Butchko is a project engineer with SouthlandIndustries National Advanced Technologies Group lo-cated in Richmond, Va.

Fielding Leroy Pope, P.E., is a senior controls engineerat Southland Industries.

By Cynthia A. Callaway, P.E.,Member ASHRAEKevin L. Davis, P.E.,Associate Member ASHRAEJanie Kuehn,Member ASHRAELanty K. Butchko,Associate Member ASHRAEandFielding Leroy Pope, P.E.Member ASHRAE

Pipe fitters install new chilled water coils in penthouse air handler.

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at the same level as the City Hall base-ment. Underground parking connects thetwo buildings.

The central plant serving both build-ings is located in a penthouse at the topof City Hall. City Hall has 204,700 ft2

(19 000 m2) of conditioned floor areawhile the library conditioned square foot-age is 125,200 (11 600 m2) and includesa 300-seat auditorium. Both facilities hadto remain open to the public and fullystaffed during the retrofit. All construc-tion was done after hours or on weekends.

Energy efficiency was addressed infive major areas: central cooling plant,air-handling systems, lighting, energymanagement control system and commis-sioning. This project replaced the entirecooling plant and converted the chilledwater distribution to a primary-second-ary pumping configuration.

Central Cooling PlantThe existing central plant consisted of

two original 550 ton (1930 kW) chillers ratedat 0.83 kW per ton and a newer 200 ton (700kW) chiller rated at 0.68 kW per ton.

The new plant consists of two 400 ton

(1400 kW) chillers rated at 0.55 kW perton, two induced draft cooling towers withtwo-speed 20 hp (15 kW) fans, two 7.5hp (5.6 kW) primary pumps, two 15 hp(11 kW) condenser water pumps and three15 hp (11 kW) variable speed secondarypumps (one is standby). The primarypumps and chillers are headered as arethe condenser water pumps and coolingtowers. Two secondary loops were in-stalled, one for the main cooling coil serv-ing floors two through fourteen of CityHall and one for the remainder of CityHall and the library.

The difference in operating hours andload profiles determined the division ofthe secondary system. Total connectedpump horsepower was reduced from 335hp to 75 hp (250 kW to 56 kW). The to-tal connected cooling tower fan horse-power was reduced from 120 hp to 40 hp(90 kW to 30 kW). Reduction in the ca-pacity and connected horsepower of thecentral plant was due to improvements inthe air-handling and lighting systems,which are discussed later, and increasingthe chilled and condenser water tempera-ture differentials.

Air-Handling SystemsThree separate air-handling systems

serve City Hall. A built-up constant-vol-ume, single-fan, arrangement double-ductsystem located in the penthouse servedfloors two through 14. The penthousesystem consisted of four 125 hp (93 kW)vane axial supply fans in parallel and two60 hp (45 kW) vane axial return fans. Thearrangement of the fans and coil bankswas conducive to a variable volume two-fan, double-duct conversion. Walls were

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C O O L I N G P L A N T

built to separate the hot deck from the cold deck. The econo-mizer louver was blanked off at the hot deck, and new coolingcoils were installed. The system’s heating load could be handledwith a single fan. Therefore, the second fan was decommis-sioned, blanked off and left in place for emergency use.

Variable frequency drives were installed for the three remain-ing supply fans and two return fans. The existing mixing boxeswere gutted and left in place with their sound attenuating dis-charge plenums. To complete the system conversion, new VAVretrofit boxes were installed upstream of the existing mixing boxes.

A built-up constant-volume, single-fan, double-duct sys-tem located in the basement servedthe first floor and basement. Thebasement system consisted of a 40 hp(30 kW) centrifugal supply fan and a15 hp (11 kW) vane axial return fan.This system was converted to a pres-sure-dependent variable volume sys-tem. The existing mixing boxes weremodified from their single-actuatorconfiguration to a dual-actuator con-figuration that would allow the hot andcold decks to function separately.Static pressure dampers are used tomaintain a constant static pressure tothe mixing boxes. Variable frequencydrives were installed on the supplyand return fan, and new cooling coilswere installed.

A package multizone system servesthe City Council Chamber. Thissystem was modified by installing anew cooling coil, reducing the motorsize, resheaving the air handler and airbalancing the system to the requiredairflow.

The library is served by fivemultizone systems and one constant-volume, single-fan, double-duct sys-tem. These systems were modified by installing new coolingcoils, reducing the motor sizes, resheaving the air handlers andair balancing the systems to the required airflow.

LightingThe existing lighting system was retrofitted with new fix-

tures using T8 lamps, electronic ballasts and specular reflec-tors. The lighting retrofit reduced the total connected lightingload by 2.6 million kWh per year.

Energy Management SystemA full direct digital control system was installed throughout

the building, adding on to an existing but much less compre-hensive system. The DDC system controls all the air handlers,chillers, cooling towers, boilers, pumps, and the VAV boxesand lights for floors two through 13. The DDC system alsoprovides extensive trending and data archiving for historicalreview of the building’s performance over time.

The DDC system sequences of operation were developed tomaximize the energy efficiency of the HVAC systems. Eachvariable speed system, the penthouse cold and hot fans and thesecondary chilled water pumps, were set up to provide onlyenough pressure to satisfy the worst case damper or valve andno more. Fixed static pressure or differential pressure setpointswere not used. This, along with oversized control valves, en-sures that the minimum transport energy is used while main-taining tight control action.

The control of the return air fan speeds was programmed todecouple the economizer dampers from the relief air damper to

minimize control loop interaction. Thereturn air fans are controlled to main-tain a slightly positive pressure in therelief/return plenum. The relief airdamper is modulated solely to main-tain building static pressure while thereturn and outside air dampers oper-ate in conventional economizer con-trol. In addition, the sequencesincluded comparative enthalpy econo-mizers, wet-bulb approach coolingtower control, and optimized chillerlead/lag control.

A full commissioning process wasundertaken prior to building turnoverto ensure compliance with the designintent and a quality building for theowner. The process consisted of pre-liminary checklists, device perfor-mance tests, and functional tests.These checklists and tests covered allmechanical and control systems. Thetests were performed by a team com-prised of the building engineer, themechanical design engineer, the con-trols design engineer, and the controlssubcontractor. In addition to thesetests, the building underwent a seven-

day “hands-off” operational test to make sure all systems werefunctioning without outside assistance.

Thermal ComfortThermal comfort was considered early in the energy study

phase of the project. Occupant activity levels and clothing wereobserved during field surveys to collect plug load data. Thebuilding occupants wear clothing with an ensemble insulationvalue ranging from 0.6 to 1.0. Most of the occupants who woresuit jackets to the office removed them upon settling into theirbusiness day. Due to the temperate climate in Long Beach, thisensemble insulation range was considered to be the same forsummer and winter. The activity level was observed to be sed-entary office work (≤1.2 met). Based on this data, the load cal-culations and equipment selections were based on spaceconditions of 72°F (22°C) and 50% RH. This space condition isslightly lower than the acceptable range of operative tempera-ture and humidity for summer.

Long Beach Civic Center during helicopterlift of new chiller.

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Figure 1: Long Beach Civic Center energy consumption.

The facility’s history of warm humid spaces prompted thedesign team to provide the system capacity necessary to main-tain a lower space temperature. The zone temperature settingsare fully adjustable to provide maximum flexibility in satisfy-ing occupant comfort and are typically set at 75°F (24°C). Zonetemperature and airflow are trended by the DDC system foruse in analyzing occupant complaints.

Indoor Air QualityIAQ for the constant volume systems was addressed by bal-

ancing each system to provide either 20 cfm (9.4 L/s) per per-son or 0.15 cfm (0.07 L/s) per square foot, whichever was larger,during all occupied periods. Occupancy levels were based on150 ft2 (14 m2) per person for office spaces, 20 ft2 (1.9 m2) perperson for conference rooms, 200 ft2 (19 m2) per person forpublic library areas and fixed seating for auditoriums. Systemsthat were converted to VAV operation were provided with out-side air injection fans and controls to maintain a constant out-side air volume. All systems had their outside air and/oreconomizer controls refurbished.

Ventilation effectiveness depends upon stratification and re-circulation. The main variable volume system serving the officetower received new air distribution devices. Modular core diffus-ers, that maintain their performance through the expected operat-ing range of a zone, were used to ensure that the airflow was wellmixed and reached the occupant level. The majority of the mainlibrary air distribution is through existing linear diffusers. In theseareas, the calculated space air quantities were increased if theairflow through the diffusers dropped below 25 cfm (12 L/s) perlinear foot of air distribution.

Operation and MaintenanceOperation and maintenance has been reduced by the elimi-

nation of equipment that was reaching or was past its servicelife. In addition, the DDC sequences were intentionally mini-mized in complexity as much as possible, while maintainingthe efficiency goal, to make it easier for the operating staff towork with on a daily basis. For example, temperature sensorsonly are used for chiller lead/lag control instead of the morecommon flow meter approach. Temperature sensors are morereliable and easier for the staff to replace if necessary. A flowmeter was installed but is used only for operator feedback andnot control. In addition, the archived performance data kept bythe system allows the operators to go back and analyze trendsin the system performance if they suspect a problem.

Cost EffectivenessFigure 1 show’s the project’s energy consumption for

September 1996 through July 1998. Actual consumptiondata for September 1994 through September 1995 is shownfor comparison. Composite baseline is the average consump-tion from the utility bills for the period beginning February1993 and ending March 1995. Adjusted baseline is the com-

posite baseline adjusted for weather, billing period lengthand changes in the utility rates. Project savings are calcu-lated from the adjusted baseline. Actual consumption istaken directly from the utility bill for the period indicated.As the variable air volume conversion progressed from Sep-tember 1996 through January 1997 the consumption droppedsteadily.

The anticipated savings for the project from the lightingand HVAC upgrades are 5.8 million kWh per year($523,600). The city wanted to maximize the improvementsto the infrastructure of the facility while retaining a ten-year payback. The project is not only self-funding but al-lowed the city to install new ceilings and fire sprinklers inthe City Hall building. For the 23-month period from Sep-tember 1996 through July 1998 the project saved 13 mil-lion kWh, reduced the demand by 1,340 kW and saved thecity in excess of $1,128,000. Since the project is exceedingits projected annual savings the payback period is projectedto be between 8 and 9 years.

ASHRAE Technology Awards are the HVAC&R industry’smost prestigious honor for efficient energy use in buildingsand environmental system performance. While the awards donot certify responsible charge or professional license status,they do recognize outstanding design innovation and success-ful implementation.

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