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Product Description
stag gered rows and mechanically expanded into cor ro sion
resistant aluminum alloy fi ns with full height fi n col lars.
They have a design working pressure of 450 PSIG
(31 bar). Each coil is rested to 495 PSIG (34 bar).
Multiple fans move air through the coils. They are
dy nam i cal ly and statically balanced, direct drive with
cor ro sion re sis tant glass fi ber reinforced composite
blades mold ed into low noise, full airfoil cross section,
pro vid ing vertical air discharge from extended orifi ces
for ef fi cien cy and low sound. Each fan is located in a
sep a rate com part ment to prevent cross fl ow during fan
cy cling. Guards of heavy gauge, PVC coated galvanized
steel are pro vid ed.
The fan motors are high effi ciency, direct drive, 6-pole,
3-phase, Class- "F," current overload protected, totally
en closed (TEAO) type with double sealed, per ma nent ly
lubricated ball bearings.
Economizer
(Models YCAS 773, 953, 1093 and 1263)
A plate and frame heat exchanger (economizer) is fi tted
to both refrigerant circuits on models YCAS 773, 953,
1093 and 1263. This increases the effi ciency of the
system by subcooling the primary refrigerant liquid to
the evaporator.
The wet vapor to the economizer is supplied by a small
15 ton TXV set for 10°F ((5.5°C) superheat the fl ashes
off 10-20% of the liquid from the condenser. 10-12 tons
are utilized for subcooling liquid refrigerant. The wet
vapor is at intermediate pressure between discharge
and suction (1.7 x suction) and therefore little energy
is required to pump it back through the compressor to
condenser pressure. This results in a very small loss to
system effi ciency.
The economizer provides 25°F (14°C) of additional
subcooling to the liquid refrigerant which fl ows to the
evaporator at 95°F (35°C) ambient, 55°F (13°C) RWT,
44°F (7°C) LWT. Subcooling will drop to approximately
0°F (32°C) ambient. The subcooled liquid is then fed
to the primary TXV in the system. This additional
subcooling results in a significant increase in the
effi ciency of the system. The design working pressure
of the economizer is 450 PSIG (31 bar). The economizer
liquid supply solenoid is activated on start-up coincident
with the liquid line solenoid, after pumpdown.
The economizer operation is controlled by the
economizer solenoid valve. This valve is controlled by
the microprocessor. The valve will remain off for the
fi rst 3 minutes of compressor operation. After 3 minutes
14
of operation, the economizer solenoid valve will open
if the slide valve position is >Step 47, and the pressure
ratio (PR) of discharge pressure to suction pressure is
greater than 2.2 using the following formula:
English:
PR
=
Metric :
PR
=
Oil Separator/System
The external oil separator, with no moving parts and
de signed for minimum oil carry-over, is mounted in
the dis charge line of the compressor. The high pressure
dis charge gas is forced around a 90 degree bend. Oil is
forced to the outside of the separator through cen trif u gal
action and captured on wire mesh where it drains to the
bottom of the oil separator and fl ows to the condenser
for cooling before returning to the compressor.
The oil (YORK "L" oil – a POE oil used for all
re frig er ant applications), which fl ows back into the
com pres sor through a replaceable 0.5 - 3.0 micron
oil fi lter, is at high pressure. This high pres sure "oil
injection" forces the oil into the com pres sor where it is
fed to the bearings for lubrication. After lubricating the
bearings, it is injected through orifi ces on a closed thread
near the suction end of the rotors. The oil is automatically
in ject ed because of the pressure difference between the
discharge pres sure and the reduced pressure at the suc tion
end of the rotors. This lubricates the rotors as well as
provides an oil seal against leakage around the ro tors to
assure re frig er ant compression (volumetric ef fi cien cy).
The oil also provides cooling by transferring much of
the heat of com pres sion from the gas to the oil keeping
dis charge tem per a tures down and reducing the chance
for oil breakdown. Oil injected into the rotor cage fl ows
into the ro tors at a point about 1.2x suction. This assures
that a required minimum differential of at least 30 PSID
(2.1 bar) exists between discharge and 1.2x suc tion, to
force oil into the rotor case. A minimum of 10 PSID
(0.6 bar) is all that is re quired to assure pro tec tion of
the compressor. Oil pressure safety is mon i tored as the
dif fer ence between suction and the pres sure of the oil
en ter ing the ro tor case.
Maximum working pressure of the oil separator is 450
PSIG (31 bar). Oil level should be above the midpoint
of the "low er" oil sight glass when the compressor is
run ning. Oil level should not be above the top of the
"up per" sight glass.
FORM 201.19-NM6 (804)
DP (PSIG) + 14.7
SP (PSIG) + 14.7
DP (BAR) + 1
SP (BAR) + 1
YORK INTERNATIONAL
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