Carrier Air Conditioner specifications Configuring Demand Limit, DLS2

Demand Limit — Demand Limit is a feature that allows the unit capacity to be limited during periods of peak energy usage. There are 3 types of demand limiting that can be config- ured. The first type is through 2-stage switch control, which will reduce the maximum capacity to 2 user-configurable per- centages. The second type is by 4 to 20 mA signal input which will reduce the maximum capacity linearly between 100% at a 4 mA input signal (no reduction) down to the user-configurable level at a 20 mA input signal. The third type uses the CNN Loadshed module and has the ability to limit the current operat- ing capacity to maximum and further reduce the capacity if required.

NOTE: The 2-stage switch control and 4 to 20 mA input signal types of demand limiting require the Energy Management Module (EMM).

To use Demand Limit, select the type of demand limiting to use. Then configure the Demand Limit set points based on the type selected.

DEMAND LIMIT (2-Stage Switch Controlled) — To con- figure Demand Limit for 2-stage switch control set the Demand Limit Select (DMDC) to 1. Then configure the 2 De- mand Limit Switch points (DLS1 and DLS2) to the desired ca- pacity limit. See Table 28. Capacity steps are controlled by 2 relay switch inputs field wired to TB6 as shown in Fig. 2-4.

For Demand Limit by 2-stage switch control, closing the first stage demand limit contact will put the unit on the first de- mand limit level. The unit will not exceed the percentage of ca- pacity entered as Demand Limit Switch 1 set point. Closing contacts on the second demand limit switch prevents the unit from exceeding the capacity entered as Demand Limit Switch

2 set point. The demand limit stage that is set to the lowest de- mand takes priority if both demand limit inputs are closed. If the demand limit percentage does not match unit staging, the unit will limit capacity to the closest capacity stage.

To disable demand limit configure the DMDC to 0. See Table 28.

EXTERNALLY POWERED DEMAND LIMIT (4 to 20 mA Controlled) — To configure Demand Limit for 4 to 20 mA control set the Demand Limit Select (DMDC) to 2. Then configure the Demand Limit at 20 mA (DM20) to the maximum loadshed value desired. The control will reduce al- lowable capacity to this level for the 20 mA signal. See Table 28 and Fig. 23.

DEMAND LIMIT (CCN Loadshed Controlled) — To con- figure Demand Limit for CCN Loadshed control set the De- mand Limit Select (DMDC) to 3. Then configure the Loadshed Group Number (SHNM), Loadshed Demand Delta (SHDL), and Maximum Loadshed Time (SHTM). See Table 28.

The Loadshed Group number is established by the CCN system designer. The MBB will respond to a Redline com- mand from the Loadshed control. When the Redline command is received, the current stage of capacity is set to the maximum stages available. Should the loadshed control send a Loadshed command, the MBB will reduce the current stages by the value entered for Loadshed Demand delta. The Maximum Loadshed Time defines the maximum length of time that a loadshed con- dition is allowed to exist. The control will disable the Redline/ Loadshed command if no Cancel command has been received within the configured maximum loadshed time limit.

Table 28 — 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
				CRT1	XXX.X °F	No Cool Reset Temperature
				CRT2	XXX.X °F	Full Cool Reset Temperature
				DGRC	XX.X ∆F	Degrees Cool Reset
							Default: 0
							0 = None
				DMDC	X	Demand Limit Select	1 = Switch
							2 = 4 to 20 mA Input
							3 = CCN Loadshed
				DM20	XXX %	Demand Limit at 20 mA	Default: 100%
							Range: 0 to 100
						Loadshed Group	Default: 0
				SHNM	XXX		Range: 0 to 99
						Number
						Loadshed Demand	Default: 0%
				SHDL	XXX%		Range: 0 to 60%
						Delta
						Maximum Loadshed	Default: 60 min.
				SHTM	XXX MIN		Range: 0 to 120 min.
						Time
						Demand Limit	Default: 80%
				DLS1	XXX %		Range: 0 to 100%
						Switch 1
						Demand Limit	Default: 50%
				DLS2	XXX%		Range: 0 to 100%
						Switch 2

NOTE: Heating reset values skipped in this example.

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