Carrier Comprehensive Guide to Shunt Trip Wiring Diagram and Safety Limits

Table 3 — Protective Safety Limits and Control Settings

MONITORED PARAMETER	LIMIT	APPLICABLE COMMENTS
TEMPERATURE SENSORS OUT OF	–40 to 245 F (–40 to 118.3 C)	Must be outside range for 2 seconds
RANGE
PRESSURE TRANSDUCERS OUT OF	0.06 to 0.98 Voltage Ratio	Must be outside range for 3 seconds.
RANGE		Ratio = Input Voltage ÷ Voltage Reference
COMPRESSOR DISCHARGE	>220 F (104.4 C)	Preset, alert setting configurable
TEMPERATURE
MOTOR WINDING TEMPERATURE	>220 F (104.4 C)	Preset, alert setting configurable
BEARING TEMPERATURE	>185 F (85 C)	Preset, alert setting configurable
EVAPORATOR REFRIGERANT	<33 F (for water chilling) (0.6°C)	Preset, configurable chilled medium for water
TEMPERATURE		(SETUP1 table)
	<EVAP REFRIG TRIPPOINT (set point adjustable	Configure chilled medium for brine (SETUP1
	from 0 to 40 F [–18 to 4 C]) for brine chilling)	table). Adjust EVAP REFRIG TRIPPOINT for
		proper cutout
TRANSDUCER VOLTAGE	<4.5 vdc> 5.5 vdc	Preset
CONDENSER PRESSURE — SWITCH	165 ± 5 psig (1138 ± 34 kPa), reset at	Preset
	110 ± 7 psig (758 ± 48 kPa)
— CONTROL	165 psig (1138 kPa)	Preset
OIL PRESSURE	Cutout <15 psid (103 kPad)	Preset
	Alert <18 psid (124 kPad)
LINE VOLTAGE — HIGH	>150% for one second or >115% for ten seconds	Preset, based on transformed line voltage
		to ISM. Also monitored at CVC/ICVC and
— LOW	<85% for ten seconds or ≤80 for 5 seconds or
		CCM power input.
	<75% for one second
— SINGLE-CYCLE	<50% for one cycle (if enabled)	Default is disabled.
COMPRESSOR MOTOR LOAD	>110% for 30 seconds	Preset
	<15% with compressor running	Preset
	>15% with compressor off	Preset
STARTER ACCELERATION TIME	150% RLA for 20 sec.	For chillers with reduced voltage mechanical
(Determined by inrush current)		and solid-state starters
	>100% RLA for 45 sec.
	>100% RLA for 10 sec.	For chillers with full voltage starters
		(Configures on ISM_CONF table).
STARTER TRANSITION	If ISM contact open >20 sec.	Reduced voltage starters only
CONDENSER FREEZE PROTECTION	Energizes condenser pump relay if	CONDENSER FREEZE POINT configured in
	condenser refrigerant temperature or condenser	SETUP1 table with a default setting of 34 F
	entering water temperature is below the configured	(1 C).
	condenser freeze point temperature. Deenergizes
	when the temperature is 5 F (3 C) above con-
	denser freeze point temperature.
DISCHARGE SUPERHEAT	Minimum value calculated based on	Calculated minimum required superheat
	operating conditions and then compared	and actual superheat are shown on
	to actual superheat.	OVERRIDE screen.
VARIABLE DIFFUSER OPERATION	Detects discharge pulses caused by	Preset, no calibration needed.
	incorrect diffuser position.

Shunt Trip (Option) — The function of the shunt trip option on the PIC II is to act as a safety trip. The shunt trip is wired from an output on the ISM to a shunt trip equipped mo- tor circuit breaker. If the PIC II tries to shut down the compres- sor using a normal shutdown procedure but is unsuccessful for 20 seconds, the shunt trip output is energized and causes the circuit breaker to trip off. If ground fault protection has been applied to the starter, the ground fault trip also energizes the shunt trip to trip the circuit breaker. Protective devices in the starter can also energize the shunt trip. The shunt trip feature can be tested using the Control Test feature.

Default Screen Freeze — When the chiller is in an alarm state, the default CVC/ICVC display “freezes,” that is, it stops updating. The first line of the CVC/ICVC default screen displays a primary alarm message; the second line displays a secondary alarm message.

The CVC/ICVC default screen freezes to enable the opera- tor to see the conditions of the chiller at the time of the alarm. If the value in alarm is one normally displayed on the default screen, it flashes between normal and reverse video. The CVC/ ICVC default screen remains frozen until the condition that

caused the alarm is remedied by the operator. Use CVC/ICVC display and alarm shutdown record sheet (CL-13) to record all values from default screen freeze.

Knowledge of the operating state of the chiller at the time an alarm occurs is useful when troubleshooting. Additional chiller information can be viewed on the status screens and the ISM_HIST screen. Troubleshooting information is recorded in the ALARM HISTORY table, which can be accessed from the SERVICE menu.

To determine what caused the alarm, the operator should read both the primary and secondary default screen messages, as well as the alarm history. The primary message indicates the most recent alarm condition. The secondary message gives more detail on the alarm condition. Since there may be more than one alarm condition, another alarm message may appear after the first condition is cleared. Check the ALARM HISTO- RY screen for additional help in determining the reasons for the alarms. Once all existing alarms are cleared (by pressing the

RESET softkey), the default CVC/ICVC display returns to normal operation.

35