York MILLENNIUM YCAS, Installation Operation & Maintenance

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24 YORK INTERNATIONAL
MOTOR STARTING
Two types of compressor motor starting are available:
Across-the-line and optional Wye-Delta Open Transi-
tion Starter.
Across-the-line starters will utilize one contactor and
one start relay per compressor. The optional Wye-Delta
starter utilizes 4 motor contactors, a transition delay re-
lay, a start relay, and a start-wye relay.
The Wye-Delta start allows inrush current to be limited
to approximately 33% LRA for the first 4 to 10 sec-
onds, with current increasing to normal running current
when the Delta connection is completed.
When the micro initiates a start signal at Terminal 20 to
run a compressor, the 1CR (SYS 1) or 2CR (SYS 2)
relay is energized. The transition of the 1CR (SYS 1) or
2CR (SYS 2) relay contacts energizes the 1S (SYS 1)
or 2S (SYS 2) relay approx. 16ms later. The 1S/2S con-
tacts in turn energize the 1M (SYS 1) or 3M (SYS 2)
motor contacts 16ms later. This completes the “WYE”
connection of the motor start. At the same time, the
normally closed 1S/2S auxiliary interlock contact opens
preventing the 2M (SYS 1) or 4M (SYS 2) motor
contactors from energizing. Auxiliary contacts from 1M
(SYS 1) or 3M (SYS 2) close, interlocking the 1M (SYS
1) or 3M (SYS 2) contactors, keeping them energized
in parallel with 1S (SYS 1) or 2S (SYS 2).
The “WYE” connection of the motor start is enabled
for 4 to 10 seconds depending upon motor current as
sensed by the microprocessor. Normally, the transition
to Delta takes 10 seconds if current is below 125% FLA.
If motor current exceeds 125% FLA, the transition is
made to Delta as long as the WYE has been enabled
for at least 4 seconds.
After the “WYE” connection is enabled for 4 to 10 sec-
onds, the 1TR (SYS 1) or 2TR (SYS 2) transition delay
relay is enabled by the microprocessor from Terminal
9. The 1TR (SYS 1) or 2TR (SYS 2) contacts open,
de-energizing 1S (SYS 1) or 2S (SYS 2). 1M (SYS 1)
or 3M (SYS 2) remain energized through interlocking
contacts 1M (SYS 1) or 3M (SYS 2). Opening of the
1TR (SYS 1) or 2TR (SYS 2) contacts closes the nor-
mally open 1S (SYS 1) or 2S (SYS 2) contacts, energiz-
ing motor contactor 2M (SYS 1) or 4M (SYS 2), com-
pleting the “DELTA” connection of the motor.
1 TR and 2TR are NOT “timing” re-
lays.
KEYPAD CONTROLS
Display
Parameters are displayed in Metric (ºC and Bar) or
English (ºF and PSIG) units, and for each circuit, the
following items can be displayed:
• Return and leaving chilled liquid, and ambient tem-
perature.
• Day, date and time. Daily start/stop times. Holiday
and Manual Override status.
• Compressor operating hours and starts. Automatic
or manual lead/lag. Lead compressor identification.
• Run permissive status. No cooling load condition.
Compressor run status.
• Anti-recycle timer and anti-coincident start timer
status per compressor.
• System suction (and suction superheat), discharge,
and oil pressures and temperatures.
• Percent full load compressor motor current per
phase and average per phase. Compressor capac-
ity control valve input steps.
• Cutout status and set-points for: supply fluid tem-
perature, low suction pressure, high discharge pres-
sure and temperature, high oil temperature, low and
high ambient, phase rotation safety, and low leaving
liquid temperature.
• Unloading limit setpoints for high discharge pres-
sure and compressor motor current.
• Liquid pull-down rate sensitivity (0.3ºC to 2.8ºC
[0.5ºF to 5ºF] /minute in 0.1º increments).
• Status of: evaporator heater, condenser fans, load
and unload timers, chilled water pump.
• “OUT OF RANGE” message.
• Up to 6 fault shut down conditions. (4 in YCAS 3-
compressor and YCAS 4-Compressor Models).
• The standard display language is English, with 4 other
languages available.
Entry – Used to confirm Set Point changes, cancel in-
puts, advance day, and change AM/PM.
Product Description