Demand Limit; Demand Limit (2-Stage Switch Controlled); Externally Powered Demand Limit; Demand Limit (Ccn Loadshed Controlled) - Carrier ComfortLink 6 Series Controls, Start-Up, Operation, Service, And Troubleshooting

LEGEND
LWT — Leaving Water (Fluid) Temperature
Fig. 16 — Space Temperature Reset
10
5.5
9
5.0
4.4 8
3.8 7
FULL COOL
3.3 6
RESET
5
2.8
4
2.2
CHANGE IN
1.7 3
LWT SET
POINT
1.1 2
1
.55
0
0
1 2 3
TEMPERATURE DIFFERENCE (EWT-LWT) DEGREES F
1.7
0 .55 1.1
TEMPERATURE DIFFERENCE (EWT-LWT) DEGREES C
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EWT — Entering Water (Fluid) Temperature
LWT — Leaving Water (Fluid) Temperature
Fig. 17 — Return Water Reset
Demand Limit —
Demand Limit is a feature that allows
the unit capacity to be limited during periods of peak energy us-
age. See Fig. 18. There are 3 types of demand limiting that can
be configured. The first type is through 2-stage switch control,
which will reduce the maximum capacity to 2 user-configurable
100
80
60
100% CAPACITY AT 4 mA
40
20
0
0
2
DESIGN RISE
∆
T
RESET
AMOUNT
NO COOL
∆
RESET T
5 9 10
4 6 7 8
2.2 5.0
2.8 3.3 3.9 4.4 5.5
75% CAPACITY AT 12 mA
4 6
DEMAND LIMIT SIGNAL – 4 - 20 mA INPUT
Fig. 18 — 4 to 20 mA Demand Limiting
percentages. 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 CCN Loadshed module and has the ability to limit the
current operating 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 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 config-
ure Demand Limit for 2-stage switch control set the Demand
Limit Select (DMDC) to 1. Then configure the 2 Demand
Limit Switch points (DLS1 and DLS2) to the desired capacity
limit. See Table 29. Capacity steps are controlled by 2 relay
switch inputs field wired to TB6.
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. 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
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 29.
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
allowable capacity to this level for the 20 mA signal.
DEMAND LIMIT (CCN Loadshed Controlled) — To con-
figure Demand Limit for CCN Loadshed control set the
Demand Limit Select (DMDC) to 3. Then configure the
Loadshed Group Number (SHNM), Loadshed Demand Delta
(SHDL), and Maximum Loadshed Time (SHTM). See
Table 29.
The Loadshed Group number is established by the CCN
system designer. The ComfortLink™ Control will respond to a
Redline command from the Loadshed control. When the Red-
line command is received, the current stage of capacity is set to
the maximum stages available. Should the loadshed control
send a Loadshed command, the ComfortLink Control will
8 10 12
38
50% CAPACITY AT 20 mA
14 16 18 20