SCE Evap Cooled Chillers

Governair pioneered the package air conditioning concept more than half a century ago and has been an industry leader ever since, holding the original patents for self-contained air conditioners using evaporative condensing technology. With the introduction of SCE evap condensing package water chillers, Governair has combined more than 50 years of experience and time-tested technology with modern, reliable components to produce a state-of-the-art system.

In the packaged outdoor chiller market (which has traditionally been limited to air cooled chillers), Governair's new SCE evap condensing package water chillers have met with tremendous acceptance by customers eager for an efficient, low cost, low maintenance chiller with a compact footprint.

SCE Chillers are both smaller and quieter than comparable air cooled reciprocating chillers, and their rugged construction is less susceptible to damage and vandalism. Most importantly, because they are based on evaporative condensing, they require significantly less energy to operate than air cooled versions, resulting in much lower utility bills.

What makes Governair's SCE evap chiller unique? Our engineers have combined extensive experience in designing and manufacturing evaporative condensing products with reliable screw compressor technology, a marriage which resulted in an efficient package chiller that provides our customers with low cost air conditioning.

The initial costs for purchasing evap condensing chillers with screw compressors is slightly higher than for air cooled reciprocating chillers. This initial outlay is quickly recouped, however, based on a number of important factors.

Governair's standard design is based on condensing temperatures of 105ºF or lower, according to specific design conditions, for any location in the continental United States. This compares to standard air cooled units which operate at condensing temperatures of approximately 130ºF.

The lower condensing temperatures result in significantly less energy consumption, making Governair's SCE Chiller extremely economical. On the average, it operates on 30 percent less energy than comparable air cooled equipment, resulting in less base energy consumption and lower demand charges.

Based on current energy prices, payback periods of less than two years are not uncommon.

The lower condensing temperature also reduces the strain on the compressors, making them last longer and reducing future maintenance costs.

Additionally, many utility companies offer rebates to building owners who install high efficiency cooling systems like the SCE Chiller, further increasing the attractiveness of this product line. Rebates as high as $70 to $200 per ton of installed equipment are not uncommon, substantially reducing the first-cost differential and reducing the payback period to less than one year!

SCE Chillers are self-contained and designed for outdoor installation, enabling building owners to make the most of their available space. They are preassembled and fully tested at the factory, reducing field labor costs for installation and increasing system reliability. Because SCE Chillers are typically 30 percent more energy efficient than air cooled chillers, the cost of bringing electrical service to the building is also proportionately reduced.

The high power factors inherent on the efficient 3500 RPM screw compressor motors used in SCE Chillers eliminates any requirements for field installation of expensive power factor correction capacitors.

With Governair's compact system design, the cabinet footprint for an SCE Chiller is 40 to 50 percent smaller than comparably sized air cooled reciprocating chillers. In urban areas where sky-rocketing real estate prices escalate the costs of new building projects, SCE Chillers have been especially well received because less space is required for the HVAC equipment.

SCE evaporative chillers are available in larger sizes than air cooled reciprocating chillers, with Governair's standard product line ranging from 45 to more than 500 nominal tons. They are versatile, requiring less air flow than air cooled condensers, and are operationally quieter due to the reduced air flow, as well as the use of screw compressors and adjustable pitch airfoil propeller fans.

This versatility makes the SCE Chiller ideal for a number of applications, especially commercial office buildings and schools. They are also extremely suitable for retrofit projects because of their compact footprint. The small wire-size requirement means that a new, more efficient chiller of higher tonnage can be installed without upgrading the electrical service, as is often the case when replacing air cooled chillers.

The low design condensing temperature makes Governair's SCE Chiller the best choice when selecting equipment for ice storage and low temperature applications.

The compressors used in standard air cooled chillers are not appropriate for the high pressure differentials required for low temperature applications. These high pressure differentials require modifications to the basic design of an air cooled chiller and reduce the life of the reciprocating compressors. Governair's SCE evaporative condensing chillers can easily provide 20ºF glycol/water solutions without modification to our standard design.

Screw compressors are rotary devices lacking pistons, a design that is both operationally quiet and extremely efficient. Because they are continuously modulating, screw compressors are ideal for use in chillers. They are constructed of high quality cast iron in a semi-hermetic design, and a suction gas-cooled motor is used for extra long like.

With an integral oil separator and oil management system, there are no external devices requiring maintenance.

In response to growing public concern about ozone-depleting chemicals which are potentially harmful to the environment, Governair uses proven, environmentally-friendly R22. R22 has been recognized by the Montreal Protocol as a replacement for the CFC-based systems used in most centrifugal chillers.

R22 is used in the SCE Chiller because it is both proven and readily-available. Other replacement refrigerants currently on the market are unproven, untested and expensive.

With all CFC-containing refrigerants scheduled for phase-out in the next few years, R22 is the best choice for engineers who are concerned about the future maintainability of the equipment they specify today.

Governair custom designed the evaporative condenser used in its SCE Chiller to obtain the most efficient, reliable operation possible. The following features are standard aspects of Governair's high quality evap condenser:

• A three inch channel base is welded to stainless steel sump and casing which is welded water-tight.
• 18 gauge 304 stainless steel upper panels have a baked-on epoxy finish.
• No raw steel edges are exposed to the wet side.
• Special spiral non-clogging wide angle spray nozzles ensure 100 percent wet coverage of the copper condenser tubes.
• Governair's unique design contains all of the perimeter metal within the stainless steel sump. This makes it impossible for water to leak externally from the condenser cabinet.
• The draw-through fan design further eliminates water leaks. The entire cabinet is under negative pressure which pulls any moisture inward into the stainless steel sump.
• PVC moisture eliminators remove any water overspray.
• High efficiency airfoil propeller has nine high strength, corrosion-resistant PVC blades. It is direct driven by a weatherproof electric motor rated for severe service.

The brazed plate heat exchanger, standard on all models up to SCE1602, is compact and extremely light weight. Because of their unique plate design and higher thermal efficiencies, brazed plate heat exchangers are extremely efficient to operate. Constructed of non-corroding 316 low carbon stainless steel for added reliability and years of trouble-free operation, brazed plate heat exchangers fit in approximately one-fifth of the space required for comparable shell-and-tube chiller barrels. This means lower hold-up volumes and simplified installations, as well as reduced shipping costs.

ASME-coded shell-and-tube evaporators with removable cast iron heads and enhanced copper tubes are standard on models SCE1952 through 5204, and optional on all other SCE Chillers.

The condenser coil is constructed of heavy duty copper tubes and headers, contained in pierced and extruded ABS tube sheets. The self-cleaning spray nozzles and spray tree are of PVC to eliminate corrosion, and assure complete water spray coverage over the copper coil. This guarantees that all heat transfer surfaces are evenly wet, reducing scaling and providing even heat rejection.

The rugged water and air tight cabinet has

• a welded tubular base and upper frame,
• 18 gauge 304 stainless steel panels
• man-sized access doors and removable panels for easy maintenance, and
• rugged vandal-resistant construction, including heavy duty wire guard that protects the fan and motor.

SCE Chillers are completely self contained, with DDC controls standard on all models. Temperature controls and compressor safety controls are factory-wired, pretested and ready for single-point wiring connections. There is space inside the SCE Chiller cabinet for a field mounted water treatment system and a 110 volt power outlet for chemical pumps, as well as factory connection points for chemical pumps, sensors and distribution equipment.

In Governair's SCE Chiller, water is sprayed over a condenser coil from a spray tree located near the top of the unit. Simultaneously, air is drawn up through the coil from below, cooling the water to the ambient wet bulb temperature. This water is then used to cool the refrigerant. The ambient wet bulb temperature is typically 17ºF less than the dry bulb temperature at design conditions.

The greater the differential, the more efficiently the Governair SCE Chiller operates.

Governair's unique design represents a vast improvement over standard air cooled chillers, which only move ambient air over a condensing surface. The amount of heat rejected by the air cooled system depends on the dry bulb temperature, and the higher the dry bulb, the less efficient the system. The evaporative condenser used in the SCE Chiller takes advantage of the latent heat of evaporation to increase the heat transfer process.

Even more significantly, the condensing temperature in the SCE Chiller can be taken even lower than 105ºF, further reducing the compressor workload and enabling the system to operate at the most efficient level possible.

Note: Low ambient freeze protection options must be considered. Governair recommends that

1. the unit be secured below 32ºF with a dump valve to discharge water from the sump when the temperature drops below 35ºF,
2. the chiller barrel be protected at all times with electric heat tape, standard on SCE Chillers,
3. for extra protection, a glycol charge be used on the chilled water loop in units installed in northern climates, and
4. a sump water heater should be installed in any units operated in cold climates (where temperatures fall below 30ºF).

SCE chillers are completely self-contained and designed for outdoor installation, enabling building owners to make the most of their available space. In urban areas where land use is limited, the cost of new building projects is frequently escalated by the additional area required for built-up systems. SCE Chillers have been especially well suited for these applications because they typically fit in the same footprint as a comparably sized cooling tower, saving all of the space required by a centrifugal chiller and condensing pump.

Governair's package approach helps lower the total system costs of the job even further. There is no need for a cooling tower or mechanical equipment room, eliminating the need for additional equipment and piping. The cost of electrical service is proportionately reduced because there is only one piece of equipment to hook up. The cabinet can also be expanded to include chilled water pumps, piping and boilers.