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Keeping the District Cool

HCPS Air Conditioning the Cold Hard Facts

September 23, 2016

The August-in-Florida humidity made the 91 degrees feel even hotter as Chris McLaughlin, an A/C Specialist 3, and his co-worker Micheal Pratt were making adjustments to the massive chiller units in a balmy mechanical room at Howard W. Blake High School.

McLaughlin and Pratt are two of the 70 employees in the air-conditioning department at Hillsborough County Public Schools. The department responds 24-hours-per-day, 7-days-per-week to ensure the safety and comfort of students, teachers and staff of the district’s 232 schools plus other sites owned and operated by the district.

McLaughlin said the district air-conditioning priorities are: air quality first, customer comfort second and cost savings third.

The department prides itself on, “Responding as fast as we can to outages and making repairs needed the first time we step foot on a school site,” said Jim Dieringer, the manager of the extremely busy department.  McLaughlin, who has nearly 30 years of experience working on air-conditioning equipment estimated, “80 percent of the time we are able to repair an issue on the first service call.”

Dieringer said the jobs are prioritized by the number and needs of the customers affected. If an entire site is down, it goes to the top of the list. Special needs students with health issues or schools with an entire wing or cluster down are also factored in. Finally, individual classrooms or areas where the air is partially working are added to the technician’s workload.

Districtwide there are more than 5500 traditional or Freon-based units and a total of 205 cold-water chillers are operating at 63 sites. Schools like Potter Elementary are equal, in air-conditioning terminology, to a small subdivision where 40 separate units are used, Dieringer said.

The department’s yearly budget is approximately $4.7 million for parts, filters, contracted vendor costs and sometimes rentals for the actual chillers themselves. The district’s power bill last school-year, while not separated out by category including lighting, air-conditioning and food preparation such as mixers and ovens, was nearly $34.2 million.

One of the challenges faced by the department are the age of the systems they are working on. Many of the district schools have systems that not only cool current students, but also cooled their parents. A large portion of the district’s cooling units are centrally controlled and monitored, but some of the older systems have to be individually controlled and monitored at each unit, delaying response time to an outage. Commercially a unit is constructed to last around 20 years.

The system McLaughlin and Pratt were working on at Blake is right at that 20-year threshold. The two original chillers remain, but they were previously retrofitted with second generation electronic controls. Two new outdoor towers were installed last month at a cost of nearly $400,000, according to McLaughlin. The employees were back out this time to make the system more efficient such as finding and repairing sensors, controllers and other electronic devices as well as controlling the flow of water on the campus.

Some issues are unknowingly created by the customers themselves. “Thermostats must have proper air flow around them to get a proper reading,” said Pratt. Sometimes with limited classroom space a teacher might place a book shelf or other piece of furniture too close to a thermostat. Computer systems or other pieces of electronic equipment also can generate heat, not found in other parts of the classroom; this can make a unit run overtime and lead to a breakdown.

Hard to find replacement parts sometimes have to be secured from other countries such as Canada or as far away as Italy. After finding these parts, the purchasing process is more intensive because these smaller foreign companies are not current vendors to the district, Dieringer explained. Because the district is a government entity proper purchasing procedures must still be adhered to.

Recruiting highly qualified technicians is an ongoing challenge for the school district. Right now the department has 18 vacancies due to the fact that wages can often be higher in the private sector. Dieringer said the Human Resources Division does assist his department with recruiting, and the district offsets industry wages with steady year-round work, a great benefit package and retirement system; but the draw of higher wages boosted by overtime pay drives many potential technicians into the private sector.

In addition to his own workforce, Dieringer explained the department also uses the services of 18 different air conditioning service vendors. Some vendors have specific roles such as the water quality of the chiller systems; another, specifically, services boilers. Three vendors specialize in the energy management system or EMS, while two more vendors are in charge of filter changes for the entire district. “A site may have anywhere from to up to 150 filters and changing them all in a single school can take the contract crew up to an entire week,” he said.

What is the process for getting the air-conditioning fixed at a school site? At many sites the automated software will let the department know there is an issue even if no one is on campus. At other sites without remote monitoring a maintenance request is initiated at the school site. Three area supervisors from the East, Central and West maintenance areas prioritize maintenance requests and assign them to crews first thing in the morning and as they come in throughout the day.

The department excels at communicating with school staff members on what needs to be done and the status of their repair. School principals are not only charged with academic and behavioral success of their students, they quickly become fluent in the vocabulary belonging to facility systems on their campuses as well.

The department can also offer alternative services to sites whose units may be down for parts. For example, Dieringer recalls a Friday afternoon three days before the beginning of this school-year one of the systems at Williams Middle Magnet School went down and the custom made parts for the system had to not only be ordered, but manufactured to meet the unit. Custom units may have to wait up to six weeks for parts to be delivered. In this case the department paired itself with a vendor to get dehumidifiers and portable air-conditioning units, known as spot coolers, out to the school until the repairs could be completed. “Fans just push the hot air around and do nothing for the humidity,” Dieringer said. The district owns some of these portable units but, as shown by the response at Williams Middle, will do whatever it takes to ensure the safety and comfort of the students and teachers.

Air quality is monitored by the safety office. They determine if air quality issues are due to the air conditioning or just other factors. If it is an air-conditioning issue, the department will coordinate its repair with retesting until the issue has been abated.

In a cold water air-conditioning system the indoor air is cooled in increments of 10 degrees. Cold water at 44 degrees Fahrenheit flows into the air exchanger and removes heat from the air until the water reaches 54 degrees. The heat difference is then pumped outdoors to the towers where water at the top starts 93 degrees and comes out the bottom at 81.5 degrees. Those 10 degrees are transferred to the outside air. You can feel the difference just by being in close proximity to the tower said Pratt, an HVAC Mechanic 2, who brings 12 years of experience to his customers at the school sites. Freon-based units work on the same principal except they use Freon gas instead of cold water to cool extract heat from the system.

Just touching a thermostat in a classroom may be enough to shut down the climate control. An employee or student attempting to control the temperature on some system could inadvertently hit a series of buttons putting the system into “holiday’ mode which may require a service visit from a technician to reset it. According to Dieringer, just keeping the windows and doors closed when the units are running goes a long, long way in keeping the systems running at maximum efficiency with minimum downtime.

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