Sterling 30RA010-055 manual Troubleshooting, Configuring Demand Limit

Table 27 — Configuring Demand Limit

MODE	KEYPAD	SUB-MODE	KEYPAD	ITEM	DISPLAY	ITEM EXPANSION	COMMENT
	ENTRY		ENTRY
CONFIGURATION	ENTER	DISP	ENTER	TEST	ON/OFF	Test Display LEDs
		UNIT	ENTER	TYPE	X	Unit Type
		OPT1	ENTER	FLUD	X	Cooler Fluid
		OPT2	ENTER	CTRL	X	Control Method
		RSET	ENTER	CRST	X	Cooling Reset Type
							Default: 0
				DMDC*	X	Demand Limit Select	0 = None
							1 = Switch
							2 = 4 to 20 mA Input
							3 = SCN Loadshed
				DM20	XXX %	Demand Limit at 20 mA	Default: 100%
							Range: 0 to 100
				SHNM	XXX	Loadshed Group	Default: 0
						Number	Range: 0 to 99
				SHDL	XXX%	Loadshed Demand	Default: 0%
						Delta	Range: 0 to 60%
				SHTM	XXX MIN	Maximum Loadshed	Default: 60 min.
						Time	Range: 0 to 120 min.
				DLS1	XXX %	Demand Limit	Default: 80%
						Switch 1	Range: 0 to 100%
				DLS2	XXX %	Demand Limit	Default: 50%
						Switch 2	Range: 0 to 100%

*Seven items skipped in this example.

TROUBLESHOOTING

Complete Unit Stoppage and Restart — Possi- ble causes for unit stoppage and reset methods are shown be- low. (See Table 28 also.) Refer to Fig. 22-26 for Component Arrangement and Control Wiring Diagrams.

GENERAL POWER FAILURE — After power is restored, restart is automatic through normal MBB start-up.

UNIT ENABLE-OFF-REMOTE CONTACT SWITCH IS OFF — When the switch is OFF, the unit will stop immediate- ly. Place the switch in the ENABLE position for local switch control or in the REMOTE CONTACT position for control through remote contact closure.

CHILLED FLUID PROOF-OF-FLOW SWITCH OPEN — After the problem causing the loss of flow has been corrected, reset is manual by resetting the alarm with the Scrolling Mar- quee as shown in Table 24.

OPEN HIGH-PRESSURE SWITCH(ES) — Determine and correct the cause of the failure. The switch automatically resets, but the unit must be reset manually by resetting the alarm with the Scrolling Marquee as shown in Table 24.

OPEN COMPRESSOR INTERNAL THERMAL PRO- TECTION — This switch provides compressor over tempera- ture protection. Determine and correct the cause of the prob- lem. The switch resets automatically, but the unit must be reset manually resetting the alarm with the Scrolling Marquee as shown in Table 24.

OPEN 24-V CONTROL CIRCUIT BREAKER(S) — De- termine the cause of the failure and correct. Reset circuit break- er(s). Restart is automatic after MBB start-up cycle is com- plete.

COOLING LOAD SATISFIED — Unit shuts down when cooling load has been satisfied. Unit restarts when required to satisfy leaving fluid temperature set point.

THERMISTOR FAILURE — If a thermistor fails in either an open or shorted condition, the unit will be shut down. Replace T1, T2, or T9 as required. Unit restarts automatically, but must be reset manually by resetting the alarm with the Scrolling Marquee as shown in Table 24.

If unit stoppage occurs more than once as a result of any of the safety devices listed, determine and correct cause before attempting another restart.

LOW SATURATED SUCTION — Several conditions can lead to low saturated suction alarms and the chiller controls have several override modes built in which will attempt to keep the chiller from shutting down. Low fluid flow, low refrigerant charge and plugged filter driers are the main causes for this condition. To avoid permanent damage and potential freezing of the system, do NOT repeatedly reset these alert and/or alarm conditions without identifying and correcting the cause(s).

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