Small Tonnage Chiller (STC)

Small Tonnage Chillers (STCs) are one part of an overall heating, ventilation, and air conditioning (HVAC) system.

STCs produce chilled water (or glycol) by cooling the chilled water loop.

All STCs need a chilled water pump to move chilled water through their pipes. For some models, manufacturers offer a chilled water pump kit as part of the total package so that the customer need not buy
one separately.

STCs chill their water (or glycol) and reject the heat removed via one of two methods…

• Air cooled condensers
• Water cooled condensers

Although it will have a higher install cost, a chilled water system can often produce a healthier, more pleasant indoor environment than a packaged rooftop unit or DX split system because it offers…

• Better humidity control
• Better temperature control
• Better air quality
• Less ducted noise in the conditioned space

Outdoor Units

The outdoor unit transfers the heat from inside the building to the outside air.

To do this, the outdoor unit contains a...

1. Condenser- transfers the heat absorbed by the refrigerant in the evaporator to the outside air. As the condenser rejects heat, the refrigerant vapor condenses back to a warm temperature liquid before entering the expansion device and evaporator.
2. Compressor- circulates the refrigerant through the refrigeration circuit. It draws low-pressure refrigerant through the connecting pipes from the evaporator inside the building, then discharges it as high-pressure refrigerant to the outdoor condenser. The outdoor unit can serve two conventional air-handling units, or may be tied in with a full featured air-handling unit.
3. Fan- pulls air through the condenser coil, transferring heat from the condenser coil to the outside air. The use of a fan increases the efficiency of the coil without increasing its size.
4. Connecting pipes- two pipes connect the outdoor refrigeration unit to the indoor unit. The suction pipe is larger and insulated. The liquid pipe is smaller.

"Splitable" Packaged Units

Although most units ship as a factory charged, unitized package, 4-15 ton, horizontal, air cooled units can be field split. The condenser section can be placed close to the outside wall and the evaporator and blower installed near the conditioning zone. Installation is possible through standard height doorways and elevators. Refrigerant piping above the ceiling takes up less space than ductwork.

• 4-10 ton units have valves to shut off the refrigerant so that the unit can be separated.
• 12 and 15 ton units ship in two pieces.
• 5-15 ton, horizontal, water cooled units also can be separated to facilitate
  moving the units through doorways and up into the ceiling location.
• Premium units can be split due to their modular construction.

Inside an Indoor package unit

Indoor packaged units offer a low profile indoor design that eliminates the need for any unsightly exterior equipment.

Floor-by-floor installation provides independent zone and temperature control, eliminating many of the complications encountered with rooftop equipment.

Basic components inside an indoor package include…

1. Cabinet
2. Compressors
3. Condenser coil
4. Evaporator coil
5. Fans
6. Filter
7. Controls

Greater, Greener NYC

The Greater Greener New York Initiative is a terrific opportunity for the HVAC community. Announced in 2007, the Greater, Greener New York is part of PlaNYC, a revolutionary declaration backed by Mayor Bloomberg.


PlaNYC sets forth a variety of environmentally conscious goals. The earliest of these actions involves an Energy Star benchmarking, for commercial buildings over 50,000 sqft, that is required by May 2011. The benchmark is easily filed for online and made public. Buildings will be required to record their energy ranking and make efforts to increase efficiency.

While energy efficiency has always been a goal for the HVAC community, the Greater, Greener New York Initiative and PlaNYC puts an even greater emphasis on it. Nearly all of NYC's hundreds of skyscrapers will be looking for creative ways to save energy. This can vary from lighting retrofits, to chiller optimization, to load-shedding. It's possible that new ways to monitor and save energy that have not yet even been implemented will come from these efforts. As a whole, the HVAC community will need to meet this challenge as one of the #1 goals moving forward.