Thermal Overload; Current Imbalance; Improper Phase Sequence - York Millennium YCAS Series Installation Operation & Maintenance

For an Across-The-Line-Start, the trip setting will be
1.35 X RLA, if all wires of each phase are routed
through the C.T. on the 2ACE Module. If half the wires
on each phase (1 of 2 or 2 of 4) are routed through the
C.T., the trip setting should be calculated as 1.35 X
RLA/2. If 1 of 4 wires are routed through the C.T., the
trip setting should be calculated as 1.35 X RLA/4. Af-
ter calculating the trip setting using the appropriate for-
mula, refer to Table 1 on pages 18-21 for the dip switch
setting. For the location of the dip switches and deter-
mining the ON position refer to the "Note" below and
Figure 62.
A switch must be pushed to the left to
place the switch in the ON position.
For a Wye-Delta Start, the trip setting will be 1.35 X
0.58 X RLA, if all wires of each phase of either the
Wye or Delta wiring are routed through the C.T. on the
2ACE Module. If half the wires on either the Wye or
Delta of each phase (1 of 2 or 2 of 4) are routed through
the C.T., the trip setting should be calculated as 1.35 X
0.58 X RLA/2. After calculating the trip setting using
the appropriate formula, refer to Table 1 on pages 18-21
for the dip switch setting.
For the location of the dip switches and determining
the ON side of the switches, refer to Figure 62, page133.
As indicated, to place a switch in the ON position re-
quires pushing the switch to the left.
It is recommended that an YORK Ser-
vice Technician or the YORK factory
be consulted before changing these
settings for any reason, since damage
to the compressor could result.
Changes should never be made unless
it is verified that the settings are in-
correct.
Anytime a dip switch change is made,
power must be cycled off and on to the
module to reprogram the module to the
new valve.
YORK INTERNATIONAL

Thermal Overload

Three PTC (positive temperature coefficient) ther-
mistors in the motor windings of each phase provides
thermal protection. The sensor resistance stays rela-
Ω
tively constant at 1k until a temperature of 130°C
(266°F) is sensed. The sensor experiences a rapid rise
in resistance beyond this temperature. Whenever the
resistance of one of the sensors reaches 13k
module trips, which ultimately de-energizes the motor's
pilot circuit. Reset is manual after the motor cools and
the sensor resistance drops to 3.25k
Current Imbalance (Loaded & Unloaded)/
Loss of Phase
A 2 second delay at start-up allows for any imbalances
resulting during normal starting conditions. After this
initial delay, the 2ACE module compares the "Operat-
ing Current" to the measured half line current. The "Op-
erating Current" is given by 0.65 X factory overload
current setting.
An unloaded compressor condition occurs when any
measured half line current is less than the "Operating
Current." A current imbalance exceeding an unloaded
level of 25% will result in the motor pilot circuit being
de-energized.
A loaded compressor condition occurs when any mea-
sured half line current is greater than or equal to the
"Operating Current." A current imbalance exceeding a
loaded level of 17% will result in the motor pilot cir-
cuit being de-energized.
Imbalance is defined as
(High Phase - Low Phase)/High Phase

Improper Phase Sequence

The 2ACE module calculates the phase sequence at
start-up using the three current transformers to deter-
mine whether the three phase sequence on the load side
of the main contactor is miswired. Upon detection of a
miswired motor load, the module will deenergize the
main contactor pilot circuit within 50 millisecond re-
sponse time.
FORM 201.18-NM4
Ω
, the 2ACE
Ω
.
2
17