UFC 4-826-10
10 July 2002
Contractors often install halocarbon refrigerant systems with the more
stringent ammonia specifications for construction efficiencies. Ammonia components
are typically more expensive but some halocarbon systems can be competitive with the
ammonia specified components by utilizing experienced ammonia installation
technicians.
2-6.4.2
Compressors. Compressors are typically of two types: reciprocating and
rotary (screw or scroll). Scroll compressors are limited to lower capacity halocarbon
systems. Rotary screw and scroll are increasingly popular due to lower maintenance
costs. Screw compressors dominate the refrigeration market. This is mainly due to
their high reliability, usually capable of operating over 50,000 hours between overhauls,
and the selection of capacities of commercially available equipment. Commercially
available motor driven capacities range from 20 kilowatts (25 horsepower) to over 1250
kilowatts (1675 horsepower). The recommended compressor for refrigeration service is
a screw type compressor that comes as a package unit. The screw compressor
package units consist of screw compressor, motor, coupling, oil separator, local logic
controller, oil pump and filter. Refer to ASHRAE Handbook HVAC Systems and
Equipment.
2-6.4.3
Condensers. Condensers are air or water-cooled. Halocarbon systems
are usually air cooled, but water-cooled units are available. Ammonia systems are
more often water-cooled. Properly sized water-cooled condensers result in greater
efficiency and lower compressor energy consumption. This is offset by considerably
higher maintenance costs, water consumption, and more complex systems than air-
cooled. Water-cooled condensers are normally used for larger systems. Refer to
ASHRAE Handbook HVAC Systems and Equipment.
2-6.4.4
Cooling Towers. Cooling towers used for condensing refrigerants are
typically the closed circuit evaporative type. Refer to ASHRAE Handbook HVAC
Systems and Equipment.
2-6.4.5
Liquid Coolers. Liquid coolers are heat exchangers that are normally
used as liquid chilling systems for secondary coolants. Refer to ASHRAE Handbook
HVAC Systems and Equipment.
2-6.4.6
blow through type using propeller direct drive fans. Coil material must be compatible
with refrigerant used and the environment. Proper air distribution, location and quantity
of evaporators depend on the load, size and layout of the refrigerated zone. Refer to
ASHRAE Handbook Refrigeration.
2-6.4.7
Piping Systems. Refer to Pipes, Tubes, and Fittings, ASHRAE
Handbook HVAC Equipment and Systems. Separate codes or standards as listed
below govern specific systems.
Refrigeration Piping: ASME B31.5 Refrigerant Piping, ASHRAE 15,
ASHRAE Handbook Refrigeration, ASHRAE Handbook HVAC Equipment
and Systems, and IIAR Ammonia Refrigeration Piping Handbook.
2-7
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