York Millennium YCAS Series Installation Operation & Maintenance Download

Page: 22 / 188

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
relay, 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 cur-
rent when the Delta connection is completed.

When the micro initiates a start signal at Relay Output
Board #1 (SYS 1) Terminal 20 or Relay Output Board
#2 (SYS 2) Terminal 20 to run a compressor, the 1CR
(SYS 1) or 2CR (SYS 2) relay is energized. The transi-
tion 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 contacts 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. Auxil-
iary 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 Relay Out-
put Board #1 Terminal 8 (SYS 1) or Relay Output Board
#2 Terminal 6 (SYS 2). 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 energizes through
interlocking contacts 1M (SYS 1) or 3M (SYS 2). Open-
ing of the 1TR (SYS 1) or 2TR (SYS 2) contacts de-
energizes 1S/2S and closes the normally closed 1S (SYS
1) or 2S (SYS 2) contacts, energizing motor contactor
2M (SYS 1) or 4M (SYS 2), completing the “DELTA”
connection of the motor.

Systems 3 and 4 operate in a similar
sequence.

1 TR, 2TR, 3TR, and 4TR are NOT
“timing” relays. These devices are sim-
ply pilot relays identical to 1CR - 4CR.

KEYPAD CONTROLS

Display
Parameters are displayed in English (°F and PSIG) or
Metric (°C and Bars) 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 capacity
control valve input steps.

• Cutout status and setpoints 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 leav-
ing liquid temperature.

• Unloading limit setpoints for high discharge pres-

sure and compressor motor current.

• Liquid pull-down rate sensitivity (0.3°C to 2.8°C

[0.5°F to 5°F] /minute in 0.1° 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).

The standard display language is English, with 4 other
languages available.

Product Description