McQuay PFSB 103.1, Руководство по эксплуатации продукта

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803 B – 04/11 D – pag. 3/24
General characteristics
Ecological HCF 134a refrigerant
McQuay has designed and optimized Stargate
TM
compressors to operate with HFC 134a, ecological refrigerant
with zero ODP (Ozone Depletion Potential) and very low GWP (Global Warming Potential) that means low value of
the “direct effect” in the formula of TEWI (Total Equivalent
Warming Impact).
Screw compressors
The newest Stargate
TM
single-screw compressor has a well
balanced compression mechanism which cancels the screw
rotor load in both the radial and axial directions. Inherent to
the basic single-screw compressor design is the virtually
load-free operation, that gives main bearing design life of 3-4
times greater than twin-screws, and eliminates expensive
and complicated thrust balancing schemes. The two exactly
opposed gaterotors create two exactly opposed compression
cycles. Compression is made at the lower and upper parts of
the screw rotor at the same time, thus cancelling the radial
loads. Also, both ends of the screw rotor are subjected to
suction pressure only, which cancels the axial loads and
eliminates the huge thrust loads inherent in twin-screw
compressors.
Oil injection is used for these compressors in order to get
high COP at high condensing pressure. PFS units are
provided with an high efficiency oil separator to maximise oil
extraction.
Compressors have a infinitely variable capacity control down
to 25% of its total capacity. This control is made by means of
capacity slides controlled by microprocessors.
Standard start is star-delta type; Soft start type is available
(as option) in order to have lower inrush current.
Evaporator
Flooded shell-and-tube evaporator operating with refrigerant in shell and water in tubes. Replaceable water tubes
are fabricated from integral finned copper and mechanically bonded to steel tube sheets. The evaporator is PED
designed, constructed, inspected and stamped. Water side working pressure is designed for 10,5 bar. Vessels
include 1” FPT spring loaded pressure relief valves. Shell and non-connection water heads are insulated with 3/4”
thick closed cell insulation. Standard configuration on water connections side is 2 passes.
Condenser
Shell-and-tube type operating with refrigerant in shell and water in tubes. Replaceable water tubes are fabricated
from integral finned copper and mechanically bonded to steel tube sheets. Condenser is designed to conform
PED. Water side working pressure is designed for 10.5 bar. Standard configuration on water connections side is 2
passes.
Operative efficiency
The majority of comfort cooling systems operate at 60% or less of building design kW for most of the year. A great
number of those operating hours occur between 50% and 60% design cooling capacity. For that reason, PFS
chiller was designed to obtain excellent part load performance. This is achieved by a combination of individual
component features that include compressor design, operating control, double heat transfer surface with only one
compressor running (dual compressors unit), refrigerant flow control.