The widespread use of split systems is an affirmation of their advantages. Foremost, they are flexible, providing many possible solutions to commercial and industrial design challenges.
They are simple, reliable, and offer superior performance. Also, split systems are economical, providing an advantageous balance of first cost and operating cost.
Flexibility :-
Flexibility is the overriding advantage of a split system. Because a split system is made up of multiple components that are connected through a custom designed refrigerant piping system, the engineer has a large variety of possible solutions available to meet architectural and physical requirements.
- The evaporator coil can be factory-installed as part of a packaged air handler or as part of a built-up air-handling unit.
- The air handler can be located anywhere in the building (within refrigerant piping length limitations).
- The condensing unit can be located outdoors where it can be architecturally concealed or, at a minimum, where it will cause the least disruption to the building’s aesthetic environment.
- The condensing unit can be located on the roof or on the ground adjacent to the building.
- Split systems can be installed in multi-story buildings. In most applications, the buildings are one-, two-, and three-story structures.Buildings up to six stories have been successfully served with traditional splitsystems. By applying special design features, the requirements of taller buildings can also be met.
- Condensing units and air handlers are built in a variety of sizes and configurations. Commercial condensing units are available in sizes between 6 and 130 tons. Packaged air handlers vary in size from 6 to 30 tons. At the large end, central station air handling units are available in sizes up to 125 tons.
- The ability to mix-and-match combinations of air handlers and condensing units enables the building designer to select equipment precisely matched to the facility’s heating airconditioning loads.
- Using multiple systems enable cooling and heating to be divided into defined building zones.
Simplicity :-
Split systems are among the simplest of systems available for commercial applications. Chilled water systems are significantly more complicated, have more components, require more maintenance, and cost more to install than split systems. Packaged rooftop systems are simpler in that there is only one major component to install, but they lack the flexibility of a split system.
Split systems are among the simplest of systems available for commercial applications. Chilled water systems are significantly more complicated, have more components, require more maintenance, and cost more to install than split systems. Packaged rooftop systems are simpler in that there is only one major component to install, but they lack the flexibility of a split system.
An air-handling unit for a split system is typically located close to the air-conditioning load. This enables air distribution using the minimum amount of ductwork and fan energy. It also permits buildings to be zoned on a floor-by-floor basis, eliminating the need for large vertical duct chases and fire dampers.
Split systems do not require large penetrations through the building walls or roof. Packaged systems, either roof- or grade-mounted, must have large penetrations for ductwork.
Reliability :-
Split system components are mature products with long manufacturing and development histories.
The 1999 ASHRAE HVAC Applications Handbook lists the following median service lives for split system components:
Performance :-
Typical Energy Efficiency Ratios (EER) for condensing units range from 10.2 to 11.8 at ARI standard conditions. When installed as a system, typical EER values for the condensing unit and air handler operating together range between 8.7 and 10.0.
As a comparison, standard-efficiency packaged rooftop air-conditioning units have typical EER values between 8.7 and 9.7. Depending upon the manufacturer, high-efficiency rooftop units may have EER values as high as 9.3 to 11.5.
Split system components are mature products with long manufacturing and development histories.
The 1999 ASHRAE HVAC Applications Handbook lists the following median service lives for split system components:
- Air-cooled condensers 20 years
- Reciprocating compressors 20 years
- Centrifugal fans 25 years
- DX coils 20 years
- Air-to-air heat pumps 15 years
Performance :-
Typical Energy Efficiency Ratios (EER) for condensing units range from 10.2 to 11.8 at ARI standard conditions. When installed as a system, typical EER values for the condensing unit and air handler operating together range between 8.7 and 10.0.
As a comparison, standard-efficiency packaged rooftop air-conditioning units have typical EER values between 8.7 and 9.7. Depending upon the manufacturer, high-efficiency rooftop units may have EER values as high as 9.3 to 11.5.
Cost :-
Energy consumption of a split system (on a kW per ton basis) is higher than a large central water chiller. But, for a single building with a total peak load less than 100 tons, a series of multiple split systems may have a life cycle cost advantage. The building designer must thoroughly evaluate all pertinent installation, operating, and maintenance costs to make an informed decision. Although a central water chiller, by itself, may use less energy on a per-ton basis, pumps, cooling towers and other energy consuming equipment, support it. Simply stated, split systems typically cost less to install and maintain.
Energy consumption of a split system (on a kW per ton basis) is higher than a large central water chiller. But, for a single building with a total peak load less than 100 tons, a series of multiple split systems may have a life cycle cost advantage. The building designer must thoroughly evaluate all pertinent installation, operating, and maintenance costs to make an informed decision. Although a central water chiller, by itself, may use less energy on a per-ton basis, pumps, cooling towers and other energy consuming equipment, support it. Simply stated, split systems typically cost less to install and maintain.
Disadvantage :-
The benefits of a split system engender several disadvantages:
The benefits of a split system engender several disadvantages:
- Propeller fan(s) used in the condensing unit can be a relatively loud noise source that may require special consideration depending on the application. Carrier offers low-sound packages that attenuate radiated noise.
- Because the air handling equipment is distributed throughout a building, consideration must be given to acoustics and noise conduction through relatively short ducts to the conditioned spaces.
- Air handling equipment near the center of the building requires special provisions to admit outdoor air. Units with economizer cycles must usually be located near an outside wall.
- Return fans are rarely used with split systems, forcing the designer to minimize return ductwork.
- An element of care is necessary to design refrigerant piping, especially for long piping runs. Improperly designed piping can cause the system to lose capacity. At worst, improperly designed piping can cause compressor failure.
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