Demand Limit; Demand Limit (2-Stage Switch Controlled); Externally Powered Demand Limit; Demand Limit (Ccn Loadshed Controlled) - Carrier 30GTN Service And Troubleshooting Manual

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 con-
figured. 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 operating capacity to maximum and further re-
duce the capacity if required.
NOTE: The 2-stage switch control and 4 to 20 mA input
signal types of demand limiting require the Energy Manage-
ment 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 De-
mand Limit Select (DMDC) to 1. Then configure the 2 De-
mand Limit Switch points (DLS1 and DLS2) to the desired
capacity limit. See Table 26. 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
demand limit level. The unit will not exceed the percentage
of capacity entered as Demand Limit Switch 1 set point. Clos-
ing 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
KEYPAD
MODE
ENTRY
CONFIGURATION
ENTER
Table 26 — Configuring Demand Limit
KEYPAD
SUB-MODE ITEM
ENTRY
DISP TEST
ENTER
UNIT TYPE
ENTER
OPT1 FLUD
ENTER
OPT2 CTRL
ENTER
RSET CRST
ENTER
CRT1
CRT2
DGRC
DMDC
DM20
SHNM
SHDL
SHTM
DLS1
DLS2
lowest demand 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 25.
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 maxi-
mum loadshed value desired. The control will reduce allow-
able capacity to this level for the 20 mA signal. See Table 26
and Fig. 21.
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 Load-
shed Group Number (SHNM), Loadshed Demand Delta
(SHDL), and Maximum Loadshed Time (SHTM). See
Table 26.
The Loadshed Group number is established by the CCN
system designer. The PIC (product integrated control) will
respond to a Redline command 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 PIC will
reduce the current stages by the value entered for Loadshed
Demand delta. The Maximum Loadshed Time is the defines
the maximum length of time that a loadshed condition is al-
lowed to exist. The control will disable the Redline/Loadshed
command if no Cancel command has been received within
the configured maximum loadshed time limit.
DISPLAY ITEM EXPANSION
ON/OFF Test Display LEDs
X Unit Type
X Cooler Fluid
X Control Method
X Cooling Reset Type
No Cool Reset
XXX.X °F
Temperature
Full Cool Reset
XXX.X °F
Temperature
XX.X F Degrees Cool Reset
X Demand Limit Select
Demand Limit at
XXX %
20 mA
Loadshed Group
XXX
Number
Loadshed Demand
XXX%
Delta
Maximum Loadshed
XXX MIN
Time

Demand Limit

XXX %
Switch 1
Demand Limit
XXX%
Switch 2
45
COMMENT
Default: 0
0 = None
1 = Switch
2 = 4 to 20 mA Input
3 = CCN Loadshed
Default: 100%
Range: 0 to 100
Default: 0
Range: 0 to 99
Default: 0%
Range: 0 to 60%
Default: 60 min.
Range: 0 to 120 min.
Default: 80%
Range: 0 to 100%
Default: 50%
Range: 0 to 100