York YCRS Series Installation, Operation And Maintenance Manual page 46

Micropanel
When the Dip Switch (S1) on the AMB board is set for
'Water Cooling', the cutout is programmable between to
44 to 70 psi (3 to 5 bar). In this mode, a setting of 44 psi
(3 bar) is recommended. If the switch is set for 'Brine
Cooling' (glycol) the cutout is programmable between
5 - 70 psi (0.3 to 5 bar). In this mode, the cutout should
typically be set to the saturated refrigerant pressure
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
equivalent cutout temperature.
High Compressor Motor Current Cutout:
This cutouts protects against excessively 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 current is monitored
using 3 current transformers (CTs) per motor, one on
each phase.
S Y S # H I G H
S Y S # H I G H
Average motor current is monitored after 7 seconds of
compressor operation. The system will be shutdown if
average motor current exceeds 115% FLA.
When a system is fully loaded, typical
motor currents may be at 60 - 85% FLA
depending on operating conditions.
Low Motor Current Cutout / Motor Protector (high
motor winding temperature cutout) / Mechanical High
Pressure Cutout / External Motor Overload:
The low motor current cutout prevents a compressor
motor running with less current than would normally
be expected. This may result from loss of refrigerant,
contactor, or power problems as well as from a com-
pressor that is not pumping due to a mechanical mal-
46
M T R C U R R
M T R C U R R
function. Motor current is monitored using 3 current
transformers (CTs) per motor, one on each phase.
S Y S # L O W
S Y S # L O W
Average motor current is monitored after 3 seconds of
compressor operation. From this time the system will
be shutdown if average motor current is less than 10%
of FLA.
Compressor motor protection modules and mechani-
cal high pressure cutouts are fitted to each system. All
these devices stop the compressor by removing power
from its motor contactor coils. This causes the CTs to
sense a zero current draw by the compressor motor and
causes a low motor current fault to be displayed. These
devices operate as follows:
Motor Over Temperature Protection:
The motor protection module protects against exces-
sive motor winding temperature by monitoring 3 or 6
sensors built into the motor windings. If the tempera-
ture becomes excessive, the module will cause power
to be removed from the compressor contactors shut-
ting down the compressor. Sensor trip resistance is 13
kW ± 3 kW. Reset is 3.25 kW ± 0.5 kW.
The module provides current overload protection us-
ing its 3 current transformers to monitor phase current.
The modules DIP switches are Factory set to trip at
120% FLA phase current, i.e. 112% of DIP SW set-
ting, the setting being 107% of FLA. Protection against
phase loss, phase unbalance as well as incorrect phase
rotation is included. The module provides a seven seg-
ment display to define the module status as follows:
0 = NO FAULT
1 = CURRENT OVERLOAD
2 = UNBALANCE > 17%
3 = UNBALANCE > 25%
4 = INCORRECT PHASE ROTATION
5 = OVER TEMP
6 = OUT OF RANGE DIP SWITCH SETTINGS
7 = UNBALANCE > 50%
8 = PHASE LOSS
FORM 201.25-NM1 (302)
C U R R / M P / H P
C U R R / M P / H P
YORK INTERNATIONAL