Product Manual PM WSC/WDC 11
HFC 134a Impeller Compared to HCFC 123 Impeller
Left: Impeller from a McQuay single stage 300 ton (1050 kW) compressor; diameter = 6.3 in. (16 cm), weight =
3.0 lb (1.4 kg)
Right: One of three impellers from a 300 ton HCFC-123 compressor; diameter = 26 in. (66 cm), weight = 27 lb.
12.2 kg)
Compact Design
Small Footprint Cuts Installation Costs
At comparable cooling capacities, HFC-134a requires less than 3.2 cfm (1.5 l/sec) per ton of refrigeration to be
circulated by the compressor. HCFC-123 requires over 18.0 cfm (8.5 l/sec) per ton. The substantial increase in
refrigerant volume requires significantly larger suction piping and compressor components in negative pressure
designs to maintain reasonable gas velocity, noise levels and refrigerant pressure losses. Conversely, the small
physical size of McQuay centrifugal chillers will:
• Permit design of smaller equipment rooms.
• Cost less to rig and install.
• And, in smaller capacities, allow transit through standard equipment room doors, permitting building
construction to proceed on schedule before receipt of the chiller equipment.
• Lower joint surface area for lower likelihood of leaks.
Bolted Design Eases Retrofit Installation
The major components; evaporator, condenser, and compressor, are bolted together and can be taken apart in
the field to facilitate difficult rigging work. The chillers are shipped assembled from the factory and
disassembled and reassembled on site under supervision of authorized McQuay service personnel. Individual
component weights are shown in the Physical Data section.
Note: The compressor must be removed if the evaporator is to be rigged in a vertical position.
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