TAMPA — With more than 200 repair requests tumbling in every day, school officials in Hillsborough County are broadening their circle of air conditioning mechanics as they struggle to control a debilitating cycle of breakdowns and sweltering classrooms."We can't leave any stone unturned," Chief Operating Officer Chris Farkas told a School Board committee on Monday.But there was little evidence of a fast cure to a problem that has been years, perhaps decades in the making.PREVIOUS COVERAGE: Hillsborough leaders ask for patience as multiple schools still suffer from broken air conditionersHillsborough spends less on plant maintenance and operations — $709 per student each year — than any of the other 66 districts in Florida, state records show.That's one reason why even schools built in the late 1990s and early 2000s are cool one day and steamy the next. While a new air conditioner should last at least 20 years, "they're not lasting 20 years. They're lasting 10, 12, 15 years," Farkas said.The number of repair requests grows each year, as does the cost of providing basic comfort while systems await repair. It's typical for the district to rent two to four temporary chillers in a year. This year, the rental chillers are running at 10 schools at a cost of $90,000 a month."From their perspective, everything's great because they have cold air blowing," Farkas said. "From our perspective, we're just throwing money away." Coming at a time when district leaders want to boost public confidence before asking voters to pay higher taxes to support the schools, the air conditioning breakdowns are a source of growing derision.Sometimes the trouble isn't even the district's fault, Farkas said. Pierce Middle School lost cool air in two of its buildings because of an electrical outage. At Walker Middle School, a pipe burst, shutting down the rental chiller. And any time a fire alarm is activated, the air conditioning shuts down to avoid spreading the flames from room to room.RELATED: Hot schools, heavy traffic and businesses caught in the middleBut it all gets rolled into a workload that has increased by 40 percent since 2011."With no increase in budget, no increase in equipment and no increase in manpower, and as the equipment gets older and needs more maintenance, this is going to continue to grow," said Robert Weggman, general manager of maintenance.That means the department has to prioritize its calls."Any room you're in if you're hot, you're the most important thing at that time," Weggman said. "But in reality if I've got a chiller down and the entire campus is hot, or if the second floor of a building is hot, we've got to go with the big one."Committee members were pleased to hear the maintenance department, which is roughly the size it was before the district built 70 new schools in the boom years, is about to hire five more technicians.They also were told the district is broadening its pool of contract companies. School Board member Susan Valdes, who attended along with former diversity supplier chief Henry Ballard, pushed to include air conditioning firms on a district list of minority vendors.District leaders hope to benefit over time from student apprenticeships in air conditioning repair.But pay disparities remain a stubborn problem. The private sector pays much better than the school district does, and sends its technicians to locations such as Las Vegas for training.READ THE GRADEBOOK: The talk of Florida educationFarkas hopes to get School Board approval for technicians to receive some training.Since the start of school, board members have been fielding angry calls and emails from parents who are concerned about their children's health and safety."Kids cannot learn unless they have cool conditions, so you're in a very tenuous situation," board member Lynn Gray told Farkas.To counter the uproar, the district put out a two-page explainer on its website that estimated it would cost an average of $3 million to replace each elementary school air conditioning system, $5 million at middle schools and $7 to $12 million at high schools.Farkas, however, described the situation as "a $980 million problem," referring to years of deferred maintenance.Contact Marlene Sokol at (813) 810-5068 or [email protected] Follow @marlenesokol.