44
EXTERNALLY POWERED DEMAND LIMIT (4 to 20 mA
Controlled) — In this example, the 4 to 20 mA Demand Limit
will be configured and the 20 mA demand limit percentage
will be set to 50%. See Table 33 and Fig. 11.
DEMAND LIMIT (CCN Loadshed Controlled) — In this
example, the CCN Loadshed Demand Limit will be config-
ured. The loadshed group will be set to 1, demand delta will
be set to 40% and the maximum loadshed time will be set to
90 minutes. See Table 34.
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. For the above example the Loadshed Demand
delta is 40%. If the chiller is operating at 80% of total capacity
when a Redline command is received, the maximum available
capacity is set to 80%. When a Loadshed command is received,
the chiller capacity will be reduced by 40%. The chiller
can now operate at a total capacity of no more than 48%
[80% – (80% x 40%)] until a Cancel Redline or Cancel Load-
shed command is received. The control will disable the
Redline/Loadshed command if no Cancel command has been
received within the configured maximum loadshed time limit.
Table 32 — Setting Switch-Controlled
Demand Limit
Table 33 — Setting Demand Limit
(4 to 20 mA Controlled;
2 to 10 vdc With 500-Ohm Resistor)
Table 34 — Setting Demand Limit
(CCN Loadshed Controlled)
KEYPAD
ENTRY
DISPLAY
RESPONSE
COMMENT
COOLING RESET
TYPE 1
DEMAND LIMIT
Scroll down to this point
Demand Limit at 20 mA
0.0%
Demand Limit Select
0
Demand Limit Select
1
Two step switch configured
COOLING
DEMAND LIMIT
Scroll down to this point
Demand Switch 1 Setpoint
80.0%
Demand Switch 1 Setpoint
75.0%
Demand Switch 2 Setpoint
50.0%
Demand Switch 2 Setpoint
40.0%
Configuration complete
ENTER
ENTER
ENTER
KEYPAD
ENTRY
DISPLAY
RESPONSE
COMMENT
COOLING RESET
TYPE 1
DEMAND LIMIT
Scroll down to this point
Demand Limit at 20 mA
0.0%
Demand Limit at 20 mA
50.0%
Demand Limit Select
0
Demand Limit Select
2
4-20 mA control configured
KEYPAD
ENTRY
DISPLAY
RESPONSE
COMMENT
COOLING RESET
TYPE 1
DEMAND LIMIT
Scroll down to this point
Demand Limit at 20 mA
0.0%
Demand Limit Select
0
Demand Limit Select
3
CCN Loadshed control
configured
Loadshed Group Number
0
Loadshed Group Number
1
Loadshed Demand Delta
0
Loadshed Demand Delta
40%
Maximum Loadshed Time
60 min
Maximum Loadshed Time
90 min
Configuration complete
ENTER
ENTER
ENTER
ENTER
ENTER
ENTER
50% CAPACITY AT 20 mA
75% CAPACITY AT 12 mA
100% CAPACITY AT 4 mA
0
2
4
6
8
10
12
14
16
18
20
DEMAND LIMIT SIGNAL (4-20 mA INPUT)
100
80
60
40
20
0
MAX.
ALLOW
ABLE LOAD (%)
Fig. 11 — 4 to 20 mA Demand Limiting