Carrier 30RAP010-060 To 20 mA Reset, Menu Configuration of 4 to 20 mA Cooling Set Point Control

Table 24 — 4 to 20 mA Reset

SUB-MODE	KEYPAD		ITEM	DISPLAY	ITEM		COMMENT
	ENTRY				EXPANSION
						0	= no reset
					COOLING RESET	1	= 4 to 20 mA input
		ENTER	CRST	1		2	= Outdoor air temp
					TYPE
RSET						3	= Return Fluid
						4	= Space Temperature
			MA.DG	5.0 F	DEGREES COOL	Default: 0° F (0° C) Reset at 20 mA
				(2.8 C)	RESET	Range: –30 to 30 F (–16.7 to 16.7 C)

NOTE: The example above shows how to configure the chiller for 4 to 20 mA reset. No reset will occur at 4.0 mA input, and a 5.0 F reset will occur at 20.0 mA. An EMM is required.

Table 25 — Menu Configuration of 4 to 20 mA Cooling Set Point Control

MODE	KEYPAD	SUB-MODE	KEYPAD	ITEM	DISPLAY	ITEM	COMMENT
(RED LED)	ENTRY		ENTRY			EXPANSION
	ENTER	DISP
		UNIT
		OPT1
		OPT2
		HP.A
		HP.B
		EXV.A
CONFIGURATION		EXV.B
		M.MST
		RSET
		DMDC
		SLCT	ENTER	CLSP	0	COOLING SETPOINT SELECT
			ENTER		0		Scrolling Stops
			ENTER		0		Flashing ‘0’
					4		Select ‘4’
			ENTER		4		Change Accepted

IMPORTANT: Care should be taken when interfacing with other control systems due to possible power supply differ- ences: full wave bridge versus half wave rectification. Con- nection of control devices with different power supplies may result in permanent damage. ComfortLink™ controls incorporate power supplies with half wave rectification. A signal isolation device should be utilized if the signal gen- erator incorporates a full wave bridge rectifier.

To use outdoor air or space temperature reset, four variables must be configured. In the Configuration mode under the sub- mode RSET, items (Configuration→OPT1→CRST), (Con-

figuration→OPT1→RM.NO), (Configuration→OPT1 →RM.F), and (Configuration→OPT1→RT.DG) must be properly set. See Table 26A — Configuring Outdoor Air and Space Temperature Reset. The outdoor air reset example pro- vides 0° F (0° C) chilled water set point reset at 85.0 F (29.4 C) outdoor-air temperature and 15.0 F (8.3 C) reset at 55.0 F (12.8 C) outdoor-air temperature. The space temperature reset example provides 0° F (0° C) chilled water set point reset at

72.0F (22.2 C) space temperature and 6.0 F (3.3 C) reset at

68.0F (20.0 C) space temperature. The variable CRST should

be configured for the type of reset desired. The variable RM.NO should be set to the temperature that no reset should occur. The variable RM.F should be set to the temperature that maximum reset is to occur. The variable RM.DG should be set to the maximum amount of reset desired. Figures 18 and 19 are examples of outdoor air and space temperature resets.

To use return reset, four variables must be configured. In the Configuration mode under the sub-mode RSET, items CRST, RT.NO, RT.F and RT.DG must be properly set. See Table 26B

—Configuring Return Temperature Reset. This example pro- vides 5.0 F (2.8 C) chilled water set point reset at 2.0 F (1.1 C) cooler ΔT and 0° F (0° C) reset at 10.0 F (5.6 C) cooler ΔT. The variable RT.NO should be set to the cooler temperature differ- ence (ΔT) where no chilled water temperature reset should oc- cur. The variable RT.F should be set to the cooler temperature difference where the maximum chilled water temperature reset should occur. The variable RM.DG should be set to the maxi- mum amount of reset desired.

To verify that reset is functioning correctly proceed to Run Status mode, sub-mode VIEW, and subtract the active set point (Run Status→VIEW→SETP) from the control point (Run Status→VIEW→CTPT) to determine the degrees reset.

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