York YCAS Series, Installation Operation & Maintenance

Page: 154 / 216

154 YORK INTERNATIONAL
FORM 201.19-NM8 (804)
S Y S # L O W C U R R / M P / H P
S Y S # L O W C U R R / M P / H P
After 225 seconds of operation with suction pressure
op er at ing above the cut-out, a 30 second transient tim er
pre vents short term fl uctuations in suction pressure due
to load ing or fan cycling from causing shutdown. If
suc tion pres sure drops below the cutout point after 225
sec onds of operation, the transient tim er is activated.
While the tran sient timer is active, suction pressure must
not drop be low 10% of the cut-out initially pro grammed
and must be greater than:
C.O. = Programmed C.O. X ( Run Time -25 )
200
This transient cutout value increases with time until af ter
30 seconds it equals the programmed cutout val ue. If the
suction pressure falls below the value as cal cu lat ed by
the formula relative to time, the system will shut down
on a low suction pressure fault. If the suc tion pressure
rises above the programmed cutout val ue, the 30 second
timer will be reset.
If the Dip Switch on the microprocessor board is set
for “Water Cooling” (see page 168), the cutout is pro-
gram ma ble between 44 - 70 PSIG (3-5 bar) for both
R-22 and R407C models. In this mode, settings of 44
PSIG (3 bar) for R-22 and R407C are recommended. If
the Switch is set for “Brine Cooling” (glycol) the cut-
out is programmable between 5 - 70 PSIG (0.3 - 5 bar)
for R-22 and R407C models. In this mode, the cutout
should typically be set to the saturated refrigerant pres-
sure equivalent to 18°F (10°C) below the temperature
of the chilled liquid.
The sludge point of the glycol MUST be
at least 20°F (11°C) below the equiv a lent
cutout tem per a ture.
The Low Superheat Cutout is to protect the compressor(s)
from liquid fl oodback due to low suction superheat. This
safety is ignored for the fi rst 30 seconds of system run-
time.
This safety can be triggered by two events. The fi rst
is when suction superheat <0.5ºF. The second is when
the pilot solenoid is closed 10 times in 2 minutes due
to low superheat.
S Y S # H I G H M T R C U R R
S Y S # H I G H M T R C U R R
The High Motor Current Safety protects against ex ces -
sive ly high motor current and shuts a system down and
locks it out after only a single occurrence of a rise in
average motor cur rent above the cutout point. Motor
cur rent is mon i tored using 3 Current Trans form ers (CTs)
per motor, one on each phase. The C.T.'s are part of the
Motor Protector Module.
Average motor current is monitored after 7 seconds of
compressor operation. The sys tem will be shut down if
average motor cur rent ex ceeds 115% FLA. This safety
only requires one shutdown to lock out a system.
FLA (full load amps) is ap prox i mate ly
1.08 x RLA (rat ed load amps). RLA is
spec i fi ed on the mo tor / chill er name-
plate and is typ i cal current de mand
un der rated operating conditions in
a ful ly load ed sys tem. When a sys tem
is fully load ed, typ i cal motor cur rents
may be 60 - 85% FLA de pend ing on
op er at ing con di tions.
Low Motor Current Cutout / Motor Protector (Hi
Motor Winding Temp Cutout) / Mechanical High
Pressure Cutout / External Motor Overload:
The Low Motor Current Safety prevents a com pres sor
motor running with less current than would nor mal ly be
expected. This may result from loss of re frig er ant, a de-
fective contactor, power problems, or from a compressor
that is not pumping due to a mechanical malfunction.
The Sensor Failure Safety prevents the system from
running when the sensors measuring superheat are not
functioning properly. This safety is ignored for the fi rst
15 seconds of system runtime.
This safety will shut down a system if either suction tem-
perature or suction pressure sensors read out of range high
or low. This condition must be present for 3 seconds to
cause a system shutdown. The safety locks out a system
after the fi rst fault and will not allow automatic restarting.
High Compressor Motor Current Cutout:
Micro Panel Contents
S Y S # 1 L O W S U P E R H E A T
S Y S # 2 L O W S U P E R H E A T
S Y S # 1 S E N S O R F A I L U R E
S Y S # 2 S E N S O R F A I L U R E