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Aging cooling equipment in the Humble Independent School
District (ISD), Humble, TX, suffered fromrepeated fail ures, w hich
meant purchasing several new com pressors each year. Because the
equip-ment couldnt keep up wit h the demands of the hot, humid
Texas climate, it spelled discomfort f or theschools students and
teachers. The district w anted to replace the cooling systems in
eight schoolswith equipment that was more reliable and energy
efficient to provide comfortable and productivelearning
environments.
Based on a competitive price, a great reliability track record
for previous chiller purchases and excel-lent technical support,
Humble ISD selected Carrier for this project. The original
air-cooled systems ineight schools w ere replaced wi th automat ed
systems utilizing thermal energy storage (TES).
Carrierssuperior-quality model 30GTN chillers and ComfortLink
controls boosted the new systems perform-ance substantially,
reducing overall energy costs by 13% , and as much as 28% in one
school, from thechiller replacement alone, saving more than
$100,000 annually.
Carrier Chillers and Controls Reduce Energy
Costs Up to 28% for Humble ISD Schools
Carriers high eff iciency 30GTN chil ler w ith ComfortLink
controls delivered energy-saving performance to oneelementary
school, reducing energy costs by 28% .
Case Study Humble ISDCase Study Humble ISD
AIRSIDE/APPLIED/CONTROLS/SERVICE/SPECIAL SOLUTION/TOTAL SYSTEM/
UNITARY
EDUCATION/HEALTH
CARE/LODGING/MANUFACTURING/OFFICEBUILDING/RETAIL/SPECIA
Project Objectives
Solution
$100,000 Annual Savings
Energy CostComparison
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Faced w ith 16- t o 22-year-old equipment that required repeated
compressor replacements and couldntmeet t he cooling demands of t
heir school buildings, Humble ISD hired ACR Engineering to assist w
ith anenergy conservation plan for schools in the distr ict. The
recommendation w as to replace the original air-cooled equipment w
ith a system t hat used thermal energy storage (TES) tanks to
provide chil led w ater stor-age for off-peak air conditioning.
Reliable chil lers were the key to make the thermal storage project
work.
Carrier was selected f or this project based on experience and
product. Humble w as currently using Carrierchil lers in the distr
ict, and was very impressed w ith their reliabil i ty. The distr
ict w as also very satisfiedw ith the service received from Carrier
on that equipment and the more than 15 years of technical
supportCarrier had provided to the distr ict. In addition, Carriers
bid for this project w as extremely competit ive.
Humble ISD purchased ten model 30GTN chil lers for seven
elementary schools and a middle school inthe distr ict. The 30GTNs
w ere selected for their superior reliabil i ty, especially w ith
the proven Carrier 06reciprocating compressors. And the multiple,
smaller compressors used on these m achines are particularlyw ell
suited to a school application, as they provide more flexible
staging for constantly varying load condi-t ions, result ing in m
aximized effi ciency and substantial cost savings.
The new equipment is controlled by a computerized energy
management system and w as designed so thatit could be reset for
thermal storage. The equipment runs in two diff erent modes,
operating at 44F w atertemperature during the day, and 40F during
thermal storage. The school distr ict also elected to install al
lnew primary pumps, new piping and automated valving to go w ith
the thermal storage. These chil lers usethe new ComfortLink control
system, which is a real benefit because it communicates well w ith
the comput-erized energy management system, said Scott. W e went
from a start/stop system to a fully automatedsystem on each
school.
The results speak for themselves. In the first four months of
cooling, the new chil lers reduced the distr ictsenergy costs by
13% overall, with one school saving as much as 28% , translating
into distr ict-w ide savingsof more than $100,000 annually.
Comfort has also improved substantially. W e couldnt get our
chil led water temperatures down w here weneeded them with the old
equipment, said Howard Kucera, Humble ISD M aintenance Manager.
Combinethat w ith 100F Texas summers wit h 98% relative humidit y
and people were uncomfortable. Being able toput good, cold w ater
into t hese buildings has really helped our comfort issue.
Project Synopsis
In comparing electric billsbefore and after the instal-lation,
we measured a 13%average reduction in energy
use just by installing moreefficient chillers. That w as
a tangible benefit we didnteven count on.
Allan Scott,energy manager and
project engineer,Humble ISD
200 0 Car ri er Corpo rat io n 05/ 00 811 -10 000
For more information, contact your nearest Carrier
Representative, call 1.800.CARRIER or visit our web site at
www.carrier.com
Project Summary
Location: Humble, TX
Building Age: 15-20 years
Project Type: Retrofit
Building Type/Size: Eightschools: Brick and block masonr
yconstruction/One-story; elemen -tary schools: 70,000 sq. ft.;
mid-dle school: 140,000 sq. ft.
Building Usage: Classrooms,
cafeterias, gymnasiums, off ices
Objectives: Increase reliabil i t yand student comf ort;
reduceoperating costs
Major Decision Drivers:Cost; history w ith Carrier prod -ucts;
sound problems wi th otherequipment
Design Considerations:Equipment had t o be designed
so it could be reset for thermalstorage
Total Cooling (tons): 1490
HVAC Equipment: Ten mod el30GTN chillers;
ComfortLinkcontrols
Unique Features: ComfortLinkControls netw orks chil lers wit
hTES tanks and comput erizedenergy management system
Project Cost Range:$1 mil l ion to $5 mil l ion
Installation Date: Summer1999
Consulting Engineer: ACREngineering
Contractor: NorthwesternM echanical
Case Study Humble ISD continued
AIRSIDE/APPLIED/CONTROLS/SERVICE/SPECIAL SOLUTION/TOTAL SYSTEM/
UNITARY
EDUCATION /HEALTH
CARE/LODGING/MANUFACTURING/OFFICEBUILDING/RETAIL/SPECIA
