York YCAS0130 manual Compressor Motor Current Limiting, Suction Temperature Limiting

Compressor Motor Current Limiting:

S Y S	#	C U R R	L	I M I	T	I	N G
S Y S	#	C U R R	L	I M I	T	I	N G

The Motor Current Limiting message indicates that a compressor motor current has reached a programmable threshold or a BAS current limit threshold, and the system is being unloaded to assure that motor current does not become excessively high causing a fault. See Anticipatory Unloading Controls Page 161 for detailed operation.

Suction Temperature Limiting:

S Y S	#	S U C T	L	I M I	T	I	N G
S Y S	#	S U C T	L	I M I	T	I	N G

This message indicates that saturated suction temperature on a system has dropped to 24°F (-4.4°C) in the water cooling mode and that any further temperature reduction could cause some icing of the evaporator tubes. Saturated suction temperature is computed by the micro by converting suction pressure to temperature. See Anticipatory unloading controls page 161 for deatailed operation. Suction limiting is not active in the glycol mode.

2.5UNIT FAULT STATUS MESSAGES

A Unit Fault will shut the entire chiller down when a preset safety threshold is exceeded. The chiller will automatically restart after the condition causing the shutdown clears. Restart will occur only after anti-re- cycle timers are satisfied and cooling demand requires additional cooling. A reset hysteresis is built into each safety so repetitive faulting and clearing will not occur in a short time period.

Continuous monitoring by the microprocessor assures that instantaneous reaction results. When the chiller is shut down on one of these safeties, a message will ap- pear on the Status display informing the operator of the problem as shown in the text that follows.

Any time that a Unit Fault occurs, the shutdown will be logged into the HISTORY BUFFER.

Low Ambient Temperature Cutout:

U N I T F A U L T

L O W A M B I E N T T E M P

The Low Ambient Temperature Safety prevents the chiller from running in very low temperatures which could cause damage due to low system pressures. This feature is programmable and can also be used to shut down the chiller at a temperature where continued run-

FORM 201.19-NM1 (204)

ning of the chiller is not economical compared to the use of “free” cooling techniques (see also Section 8.2

/Low Ambient Temperature Cutout [page 168]). The fault will clear when ambient temperature rises 2°F (1°C) above the cut-out.

High Ambient Temperature Cutout:

U N I T F A U L T

H I G H A M B I E N T T E M P

The High Ambient Temperature Safety protects the chiller from running in ambients above 130°F (54°C) where potential malfunction of system mechanical and electrical components may result. The High Ambient Cutout is programmable and can be set for lower limit values if required (see also Section 8.2 / High Ambient Temperature Cutout [page 168]). The fault will clear when ambient temperature drops 2°F (1°C) below the cut-out.

Low Leaving Chilled Liquid Temperature Cutout:

U N I T F A U L T

L O W L I Q U I D T E M P

The Low Liquid Temperature Safety assures that the evaporator is not damaged from freezing due to im- properly set control points. It also attempts to protect the chiller from freezing, if the flow switch should fail. However, the flow switch should always be regarded as the primary safety. Whenever the chilled liquid temperature drops below the programmable cutout, the chiller will shut down (see also Section 8.2 / Leaving Water Temperature Cutout, page 168). The chiller fault will clear when temperature rises 4°F (2°C) above the cut-out and cooling demand exists.

115VAC Under Voltage Cut-Out:

U N I T F A U L T

1 1 5 V A C U N D E R V O L T A G E

The Under Voltage Safety assures that the system is not operated at voltages where malfunction of the mi- croprocessor could result in system damage. Whenever the microprocessor senses an on-board control power supply failure while a compressor is running, the chiller is shut down. The microprocessor circuitry is capable of operating at voltages 10% below the nominal 115VAC supply to the panel. Auto-restart of the chiller oc- curs after a 2 minute start-up timer has elapsed from the time when power is reapplied, if the AUTO RE- START ON POWER FAILURE is enabled. Otherwise the chiller must be manually reset. See Section 8.2 (page 170).

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