Compressor
Guide Vanes
Fully modulating variable inlet guide vanes provide capacity control. The guide vanes are controlled by an externally mounted electric vane operator in response to refrigeration load on the evaporator.
Impellers
Fully shrouded impellers are high strength aluminum alloy and directly connected to the motor rotor shaft operating at 3,600 rpm (60 hertz),
3,000 rpm (50 hertz). Impellers are dynamically balanced and over-speed tested at 4,500 rpm; the motor- compressor assembly is balanced to a maximum vibration of .15 inch/ second at 3600 rpm as measured on the motor housing.
Compressor Casing
Separate volute casings of refrigerant- tight, close-grained cast iron are used on the centrifugal compressor; each incorporating a parallel wall diffuser surrounded by a collection scroll. The diffuser passages are machined to ensure high efficiency. All casings are proof-tested and leak-tested.
Motor
Compressor motors are hermetically sealed two-pole, low-slip squirrel cage, induction-type. They are built in accordance with Trane specifications and guaranteed by the manufacturer for continuous operation at the nameplate rating. A load limit system provides protection against operation in excess of this rating. The rotor shaft is of heat- treated carbon steel and designed such that the first critical speed is well above the operating
speed. The control circuit prevents motor energization unless positive oil pressure is established. Impellers are keyed directly to the motor shaft and locked in position. Nonferrous, labyrinth-type seals minimize recirculation and gas leakage between the stages of the compressor. 200- through 600-volt, three-phase, 60- hertz and 380 through 415 volt three phase 50 hertz motors are supplied with six terminal posts for full voltage (across- the-line) or reduced voltage (Star-Delta or autotransformer) starting. For low
voltage, full voltage starting — connecting links are furnished to convert the motor to a 3-lead motor. 2,300- through 4,160-volt, three-phase, 60-hertz and 3300 through 6600 volt three phase 50 hertz motors are supplied with three terminal posts for full voltage (across- the-line) or reduced voltage (primary reactor or autotransformer) starting. Motor terminal pads are supplied. A removable sheet metal terminal box encloses the terminal board area.
Motor Cooling
Cooling is accomplished by liquid refrigerant pumped through the motor with a patented refrigerant pump. The refrigerant circulates uniformly over the stator windings and between the rotor and stator. The windings of all motors are specifically insulated for operation within a refrigerant atmosphere.
Lubrication
A direct-drive system, positive- displacement oil pump driven by a low voltage 3/4 horsepower, 120/60/1 or 120/50/1 motor is submerged in the oil sump to assure a positive oil supply to the two compressor bearings at all times. A low watt-density heater maintains the oil temperature which minimizes its affinity for refrigerant. Oil cooling is provided by refrigerant.
Evaporator
Shell and Waterboxes
The evaporator shell is formed of carbon steel plate and incorporates a carbon rupture disc in accordance with the ANSI/ASHRAE 15 Safety Code. A refrigerant temperature coupling is provided for customer use or for use with a low limit controller.
For all units, pass arrangements are available at 150 psig or 300 psig water side working pressures, with grooved connections. Flanged connections are also available. Marine-type waterboxes are available.
Tube Sheets
A thick carbon steel tube sheet is welded to each end of the shell and is drilled and reamed to accommodate the tubes.
Three annular grooves are machined into each tube hole to provide a positive liquid and vapor seal between the refrigerant and water side of the shell after tube rolling. Intermediate tube support sheets are positioned along the length of the shell to avoid contact and relative motion between adjacent tubes.
Tubes
Individually replaceable externally finned seamless copper tubing, either internally enhanced (one-inch nominal diameter) or (three-quarter inch nominal diameter) is utilized as the evaporator heat transfer surface. Tubes are mechanically expanded into the tube sheets (and affixed to the intermediate support sheets with the clips) to provide a leak- free seal and eliminate tube contact and abrasion due to relative motion.
Eliminators
Multiple layers of metal mesh screen form the eliminators and are installed over the tube bundle along the entire length of the evaporator to prevent liquid refrigerant carryover into the compressor.
Refrigerant Distribution
A refrigerant distribution compartment in the base of the evaporator assures uniform wetting of the heat transfer surface over the entire length of the shell and under varying loads. High velocity refrigerant spray impingement on the tubes is prevented through this design.
Refrigerant Flow Control
A multiple orifice flow control system maintains the correct pressure differential between the condenser, economizer and evaporator over the entire range of loading. This patented system contains no moving parts.
Shell Tests
The refrigerant side of the evaporator shell, complete with tubes, but without waterbox covers, is proof-tested at
45 psig, vacuum leak-tested and pressure leak-tested. The water side of the shell, with waterboxes in place, is hydrostatically tested at one and one- half times the design working pressure, but not less than 225 psig. (These tests are not to be repeated at installation).
