York YCAS0295EB, Installation Operation & Maintenance

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119 YORK INTERNATIONAL
FORM 201.19-NM7 (804)
Included on the I/O Expansion Board are the outputs for
the slide valve control. This control consists of a Digital
to Analog Converter (DAC) and power tran sis tors to
modulate current through the slide valve so le noids.
Relay Output Boards
One Relay Output Board per system operates the mo tor
contactors/starters, solenoid valves, and heaters which
control system operation.
The relay boards are located in the logic section of
the control panel(s). The boards convert 0 - 12VDC
logic lev els outputs from the Microprocessor Board to
115VAC lev els used by the contactors, valves, etc.
The common side of all relays on the Relay Output
Board is connected to +12VDC REG. The open col lec tor
out puts of the Microprocessor Board energize the DC
re lays or triacs by pulling the other side of the relay
coil/triac to 0VDC. When not energized, both sides of
the relay coils or triacs will be at +12VDC potential.
1.6 CIRCUIT BREAKERS
Three Circuit Breakers are provided for the 115VAC
con trols.
• CB1 allows removal of control pow er from Sys tem
1 for control sys tem cir cuit ry ser vic ing: spe cifi cal ly,
the 115VAC feed to Relay Out put Board 1 which
en er giz es contactors, so le noids, and system #1
compressor heater.
• CB2 allows removal of control pow er from Sys tem
2 for control sys tem cir cuit ry ser vic ing: spe cifi cal ly,
the 115VAC feed to Relay Out put Board 2 which
en er giz es contactors, so le noids, and system #2
compressor heater.
• CB3 allows removal of control power to the Mi-
cro pro ces sor Board, Pow er Supply Board, I/O
Ex pan sion Board, and Evap o ra tor Heater.
The Circuit Breakers remove 115VAC
con trol power only. High voltage cir-
cuit ry will still be en er gized from the
high volt age sup ply.
REMOVING 115VAC power to CB3 or
open ing CB3 removes pow er from the
evap o ra tor heat ers. This could cause
evap o ra tor freeze-up in low am bi ent
tem per a tures. Removing power from
or opening CB1 or CB2 removes power
from the respective compressor heater
and should be avoided.
1.8 TRANSFORMERS
3 Transformers (2T, 3T, and 4T) are lo cat ed in the
Con trol Panel. These trans form ers convert the 115VAC
Control Pow er Input to 24VAC to operate the mi cro pro -
ces sor circuitry.
2T: This 75VA transformer supplies the 24VAC
to the power supply board.
3T: Supplies the I/O Expansion Board # 1 voltage
for slide valve control.
4T: Supplies 24VAC power to the 2ACE Motor
Protector Modules.
1.9 MOTOR PROTECTION MODULES
A Motor Protection Module for each compressor is lo-
cat ed in the Control Panel. These modules supply mo tor
over-temperature protection, 3-phase current pro tec tion,
phase imbalance, phase rotation, and a 7 segment display
for use when programming or troubleshooting.
The motor over-temperature protection is supplied by
3 temperature sensors imbedded in the motor wind ings
120 degrees apart. The module monitors these sensors,
allowing it to sense a hot winding and shut down the
compressor if motor cooling is inadequate.
The on-board C.T.s provide 3-phase cur rent pro tec tion.
The C.T.s look at current on each phase of power to the
motor and send an analog signal proportional to aver-
age motor cur rent to the I/O Expansion board and on to
the mi cro pro ces sor board for microprocessor low/high
current pro tec tion and current display. This allows the
micro to monitor cur rent and shut a system down if low
or high motor cur rent is sensed. This is a non-adjustable
pro tec tion cir cuit electronically sized to a system's mo-
tor spec i fi ca tions.
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