Carrier 50FK, JK034-074, 48FK Ð Single-Step Demand Limit, Ð Two-Step Demand Limit Module

Connect the potentiometer end terminals to terminals 8 and 9 on control terminal block TB3 (sizes 034-048) or TB4 (sizes 054-104) (see Fig 27). Connect the switch terminals to the potentiometer wiper arm terminal and to terminal 10 on TB3 or TB4.

To enable demand limit function, change DIP switch 5 to position ON. (Disconnect control power before changing DIP switch positions. Reconnect power after all changes have been made.)

Set the potentiometer P4 to desired capacity reduction value.

Two-Step Demand Limit Ð Install the demand limit con- trol module (DLCM) according to the installation instruc- tions provided with the accessory. Disconnect existing leads at connector J3 on the processor board (see instructions) and connect the plug from the DLCM harness to connector J3.

Connect the ®eld input control power wires (from the ex- ternal control relays) at the terminal strips marked IN1, RTN1, IN2 and RTN2 (see Fig. 28 and 29).

To enable demand limit function, change DIP switch 5 to position ON. (Disconnect control power before hanging DIP switch positions. Reconnect power after all changes have been made.)

Set the potentiometers DLCM-P1 and DLCM-P2 to de- sired capacity reduction values.

Check the operation of demand limit function by using the Quick Test procedures.

CONFIGURATION

Single-Step Demand Limit Ð Field-installed potentiom- eter P4 establishes capacity reduction value for demand limit operation. Set this potentiometer between 0% and 100%. The exact percentage of capacity reduction differs depending on the number of capacity steps.

Two-Step Demand Limit Ð Potentiometer P1 and P2 (lo- cated on the accessory demand limit control module) estab- lish the capacity reduction values for each step of demand limit. Set potentiometer DLCM-P1 between 50% and 100%. Set potentiometer DLCM-P2 between 0% and 49%. The ex- act percentage of capacity reduction differs depending on the number of capacity steps.

OPERATING SEQUENCE

Single-Step Demand Limit Ð If the ®eld control switch to the wiper arm terminal is open, all capacity stages will be available (no demand limit in effect). When the ®eld control switch is closed, the compressor cooling capacity is reduced by the amount set on potentiometer P4.

When demand limit is in effect, the LED display will show

code 22 . If a potentiometer setting or input is out of range,

the control will terminate the demand limit function and show

code 84 at the display LED.

Two-Step Demand Limit Ð If the ®eld control switches are both open (no power supplied to the Demand Limit Control Module), all capacity stages will be available (no demand limit in effect). When control power is supplied to terminal IN1 only (®eld switch SW1 closes), the ®rst step of the de- mand limit is energized and the compressor cooling capacity is reduced by the amount set on potentiometer DLCM-P1. When control power is supplied to terminal IN2 (®eld switch SW2 closes), the second step of the demand limit is ener- gized and compressor cooling capacity is reduced by the amount set on potentiometer DLCM-P2.

When demand limit is in effect, the LED display will show code 22 . If a potentiometer setting or input is out of range, the control will terminate the demand limit function and show code 84 at the display LED.

034-048: TB3

054-104: TB4

8
9	5-20K
	POTENTIOMETER
	(P4)

10

SWITCH

Fig. 27 Ð Single-Step Demand Limit

Fig. 28 Ð Two-Step Demand Limit Module

NOTES:

1.Demand limit switches are ®eld supplied and wired.

2.Demand limit control module terminal blocks will accept up to 12-gage wire.

3.is ®eld wiring.

Fig. 29 Ð 115-Volt Field Wiring to Accessory

2-Step Demand Limit Control Module

Control From Remote Building Management Sys- tem (BMS) Ð The unit control system is not a commu- nicating control system, and it cannot be accessed directly by a DDC (Direct Digital Control) control system (or by a BACnet communication system). However, it is possible to control some functions of these units via 4 to 20 mA or 2 to 10 vdc signals and discrete inputs (relay contact closures).

Functions that can be managed from or accessed from an external control system include:

·Occupied/Unoccupied Status

·Night Setback Control

·Unit Supply Air Set Point Adjustment

·Demand Limit (1-stage or 2-stage)

·Supply Duct Pressure Set Point Adjustment

·External Alarm Signal

Remote control of the economizer cycle on these units is not recommended. Refer to the Operating Sequence section on page 35 for a discussion on the economizer cycle operation.

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