Chilling Case Histories
May 11, 2009
Innovations in chiller technology are being given real-world applications constantly.
Here are some recent case histories.
TALL AND NARROWWhen Dan Foley of Foley Mechanical in Lorton, Va., was asked to create cooling for a 6,500-square-foot colonial home in Maryland, the limited space in the yard prevented the installation of the five traditional condensing units that would have been necessary to cool the large home. So Foley recommended installing two tall and narrow chillers.
Foley began by installing a traditional duct system in the interior of the home, along with five indoor air handlers. The size of the home dictated the usage of commercial-grade handlers in conjunction with the traditional duct system. Other features typically used in a commercial application that were installed include a four-pipe system, staging controls, indirect domestic hot water, steam humidifiers, and ECM motors. The system would have required five exterior traditional condensers, and the space available would not accommodate them.
Foley considered the property line, which sat only five feet away from the home, and determined the best solution would be two UniChillers from Unico (www.unicosystems.com), which have the capacity to perform the same duties as five traditional condensing systems. These UniChillers were then connected to the commercial air handlers to feed the traditional duct system. Foley was able to stage the chillers for peak efficiency during light and heavy loads and take advantage of the principle of diversity loading.
WATER TREATMENTChemical-free water treatment processes on HVAC chillers were a key aspect of energy, environmental, and operational improvements at schools throughout the city of Nashville and Davidson County in Tennessee.
“It has been a massive project,” said Joe Edgens, Metropolitan board of education executive director of facilities and operations, “and it is an accomplishment that communities across the state of Tennessee can be proud of. The school district is not only saving millions of dollars as a result of reducing energy consumption, the schools in the system are better, more comfortable learning environments for our students, teachers, and everyone who either works in or visits public education facilities in Nashville.”
The project was awarded to Siemens Building Technologies Inc. (www.usa.siemens.com/building technologies). HVAC improvements were made to more than 30 schools, as well as completing lighting retrofits at 110 schools in the system. Water conservation measures were instituted at over 50 area schools and chemical-free water treatment systems were installed at 93 schools. More than 70 schools received building controls upgrades, and in 15 schools Siemens installed building automation systems.
More than 100 million gallons of water are being conserved through the implementation of system-wide conservation measures and the implementation of the chemical-free water treatment process on the chillers, according to Siemens.
During the contract period, all area schools and school facilities, encompassing 187 structures, more than 14 million square feet, and 5,000 classrooms were involved.
REVERSE CYCLEA residential application in Bethany Beach, Del., involved use of what is called a reverse cycle chiller from Aqua Products (www.aquaproducts.us).
The approach uses two insulated water pipes and a buffer tank that delivers water to a closed-loop system for hot-water heating or chilled-water cooling.
The home is a single-story, 2,400-square-foot ranch. Owner Walt Kirchoff said, “Because of the high cost of LP gas, I needed to do something to cut my energy bills. I chose (the reverse cycle chiller) because I didn’t have to drill expensive wells or dig up my yard for a geothermal system.”
The new unit replaced a 10 SEER, 5-ton air conditioning unit and a propane furnace system.
“I replaced the air conditioning system with a 5-ton, 18 SEER reverse cycle chiller. It was built using a two-speed air-source heat pump. This system was designed and installed as a dual-fuel system by installing a 5-ton cased water coil under my existing propane furnace, along with 50-gallon buffer tank and pump.
“The installed and rewired Aqua Products RCS-MAX operates as my primary source of heat with the gas furnace acting as my backup heat source if the heat pump would ever fail. This was done because the furnace was only six years old and there would be fewer invasions of the original system and wiring.
“The water temperature was set at 120°F with 2° differential first stage and 4° differentials for the second stage. After two weeks, we dropped the water temperature down to 110° with the same differentials. We average 40° to 50° daytime outdoor temperatures and 25° to 30° nighttimes. So, trying to save more money, I dropped the water temperature down to 108° where it is still at today. I also turned off my LP gas back-up heating completely before we had our cold winter temperatures.
“The indoor temperature never fluctuated from 70°. The quality of the heat was actually better than my LP gas furnace, without the hot or cold feelings we experienced with just the LP furnace. The RCS-MAX keeps our home comfortable without the need for any backup heating.”
PURGINGRefrigerant contaminants have long been a problem for chillers and the mechanical contractors who service them.
Recently, James Samsa, service manager for Dillett Mechanical Services in New Berlin, Wis., discovered a more permanent solution to contamination problems.
“One of our clients, Southern Bell Company, had three centrifugal chillers that weren’t performing like they should,” Samsa said. “They had been running them at low loads, so I figured they had oil in the evaporator. When I got a chance to check them out, I found I was right. They asked what I could do, and I told them the options, one of which was install a new oil purger I had been reading about. That’s the one they chose.”
The purger Samson was talking about was the OAM Purger LPC200 from Redi Controls (www.redicontrols.com). It was designed to remove not only oil, but also moisture and acids from a chiller. The particular one he ordered is a new model that has only been available for a few months.
The purger doesn’t rely on pumps. It uses the properties of gravity, heat, and pressure to remove contaminants.
“The refrigerant is removed in quantities of 10 to 20 pounds each cycle,” said Redi Controls’ Mark Key. “A distillation heater then heats the refrigerant and causes it to boil off and be returned to the evaporator cleaned of contaminants. When the oil reaches a temperature of 145°, effectively purifying it, it is then returned to the oil sump. Excess oil can be pulled out and stored in containers. The system cleans between 850 and 1,250 pounds of refrigerant weekly and operates whether the chiller is on or not.”
Publication date: 05/11/2009