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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 — 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 field 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 — 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 — 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 — If the field control switch to
the wiper arm terminal is open, all capacity stages will be
available (no demand limit in effect). When the field 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
22
code . If a potentiometer setting or input is out of range,
the control will terminate the demand limit function and show
84
code at the display LED.
Two-Step Demand Limit — If the field 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 (field switch SW1 closes), the first 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 (field switch
SW2 closes), the second step of the demand limit is ener-
gized and compressorcooling capacity is reduced by theamount
set on potentiometer DLCM-P2.
When demand limit is in effect, the LED display will show
22
code . If a potentiometer setting or input is out of range,
the control will terminate the demand limit function and show
84
code at the display LED.
Control From Remote Building Management Sys-
tem (BMS) —
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.
034-048: TB3
054-104: TB4
8
9
10
5-20K
POTENTIOMETER
(P4)
SWITCH
Fig. 27 — Single-Step Demand Limit
Fig. 28 — Two-Step Demand Limit Module
NOTES:
1. Demand limit switches are field supplied and wired.
2. Demand limit control module terminal blocks will accept up to
12-gage wire.
3.
is field wiring.
Fig. 29 — 115-Volt Field Wiring to Accessory
2-Step Demand Limit Control Module
19