55
DEMAND LIMIT CONTROL
Demand Limit Control may override the cooling algorithm and
clamp or shed cooling capacity during run time. The term De-
mand Limit Control refers to the restriction of the machine ca-
pacity to control the amount of power that a machine will use.
Demand limit control is intended to interface with an external
Loadshed Device through CCN communications, external
switches, or 4 to 20 mA input.
The control has the capability of loadshedding and limiting in 3
ways:
• Two discrete inputs tied to configurable demand limit set
point percentages.
• An external 4 to 20 mA input that can reset capacity back
linearly to a set point percentage.
• CCN loadshed functionality.
NOTE: It is also possible to force the demand limit variable (
Run
Status
COOL
DEM.L
).
To use Demand Limiting, select the type of demand limiting to
use. This is done with the Demand Limit Select configuration
(
Configuration
DMD.L
DM.L.S
).
To view the current demand limiting currently in effect, look at
Run Status
COOL
DEM.L
.
The configurations associated with demand limiting can be
viewed at the local display at
Configuration
DMD.L
.
See
Table 39.
Demand Limit Select (DM.L.S)
This configuration determines the type of demand limiting.
• 0 = NONE — Demand Limiting not configured.
• 1 = 2 SWITCHES — This will enable switch input de-
mand limiting using the switch inputs connected to the
CEM board. Connections should be made to TB202 termi-
nals 1, 2, 3, and 4.
• 2 = 4 to 20 mA — This will enable the use of a remote 4 to
20 mA demand limit signal. The CEM module must be
used. The 4 to 20 mA signal must come from an externally
sourced controller and should be connected to TB202 ter-
minals 10 and 11.
• 3 = CCN LOADSHED — This will allow for loadshed and
red lining through CCN communications.
Two-Switch Demand Limiting (
DM.L.S = 1
)
This type of demand limiting utilizes two discrete inputs:
• Demand Limit Switch 1 Setpoint (
D.L.S1
) — Dmd Limit
Switch Setpoint 1 (0 to 100% total capacity)
• Demand Limit 2 Setpoint (
D.L.S2
) — Dmd Limit Switch
Setpoint 2 (0 to 100% total capacity)
The state of the discrete switch inputs can be found at the local
display:
Inputs
GEN.I
DL.S1
Inputs
GEN.I
DL.S2
The following table illustrates the demand limiting (
Run Sta-
tus
COOL
DEM.L
) that will be in effect based on the logic
of the applied switches:
4-20 mA Demand Limiting (
DM.L.S = 2
)
If the unit has been configured for 4 to 20 mA demand limit-
ing, then the
Inputs
4-20
DML.M
value is used to deter-
mine the amount of demand limiting in effect (
Run Sta-
tus
COOL
DEM.L
)
. The Demand Limit at 20 mA (
D.L.20
)
configuration must be set. This is the configured demand limit
corresponding to a 20 mA input (0 to 100%).
The value of percentage reset is determined by a linear interpo-
lation from 0% to
“D.L.20”
%
based on the
Inputs
4-20
DML.M
input value.
The following examples illustrate the demand limiting (
Run
Status
COOL
DEM.L
) that will be in effect based on
amount of current seen at the 4 to 20 mA input,
DML.M
.
CCN Loadshed Demand Limiting (
DM.L.S
= 3)
If the unit has been configured for CCN Loadshed Demand
Limiting, then the demand limiting variable (
Run Status
COOL
DEM.L
) is controlled via CCN commands.
The relevant configurations for this type of demand limiting are:
Loadshed Group Number (
SH.NM
) — CCN Loadshed
Group number
Loadshed Demand Delta (
SH.DL
) — CCN Loadshed
Demand Delta
Maximum Loadshed Time (
SH.TM
) — CCN Maximum
Loadshed time
The Loadshed Group Number (
SH.NM
) corresponds to the
loadshed supervisory device that resides elsewhere on the CCN
network and broadcasts loadshed and redline commands to its
associated equipment parts. The
SH.NM
variable will default to
zero, which is an invalid group number. This allows the loadshed
function to be disabled until configured.
Upon reception of a redline command, the machine will be pre-
vented from starting if it is not running. If it is running, then
DEM.L
is set equal to the current running cooling capacity (
Run
Status
COOL
C.CAP
)
.
Upon reception of a loadshed command, the
DEM.L
variable is
set to the current running cooling capacity (
Run Status
COOL
C.CAP
)
minus the configured Loadshed Demand
Delta (
SH.DL
)
.
Table 39 — Demand Limit Configuration
Switch Status
Run Status
COOL
DEM.L = 1
Inputs
GEN.I
DL.S1
= OFF
Inputs
GEN.I
DL.S2
= OFF
100%
Inputs
GEN.I
DL.S1
= ON
Inputs
GEN.I
DL.S2
= OFF
Configuration
DMD.L
D.L.S1
Inputs
GEN.I
DL.S1
= ON
Inputs
GEN.I
DL.S2
= ON
Configuration
DMD.L
D.L.S2
Inputs
GEN.I
DL.S1
= OFF
Inputs
GEN.I
DL.S2
= ON
Configuration
DMD.L
D.L.S2
D.L.20
= 80%
D.L.20
= 80%
D.L.20
= 80%
DML.M
= 4mA
DML.M
= 12 mA
DML.M
= 20mA
DEM.L
= 100%
DEM.L
= 90%
DEM.L
= 80%
ITEM
EXPANSION
RANGE
UNITS
CCN POINT
DEFAULT
DMD.L
DEMAND LIMIT CONFIG.
DM.L.S
Demand Limit Select
0 to 3
DMD_CTRL
0
D.L.20
Demand Limit at 20 ma
0 to 100
%
DMT20MA
100
SH.NM
Loadshed Group Number
0 to 99
SHED_NUM
0
SH.DL
Loadshed Demand Delta
0 to 60
%
SHED_DEL
0
SH.TM
Maximum Loadshed Time
0 to 120
min
SHED_TIM
60
D.L.S1
Demand Limit Sw.1 Setpt.
0 to 100
%
DLSWSP1
80
D.L.S2
Demand Limit Sw.2 Setpt.
0 to 100
%
DLSWSP2
50
Содержание Weathermaster 48P2030-100
Страница 130: ...130 Fig 19 Typical Power Schematic Sizes 040 075 Shown ...
Страница 131: ...131 Fig 20 Main Base Board Input Output Connections ...
Страница 132: ...132 Fig 21 RXB EXB CEM SCB Input Output Connections ...
Страница 133: ...133 Fig 22 Typical Gas Heat Unit Control Wiring 48P030 100 Units Shown ...
Страница 134: ...134 Fig 23 Typical Electric Heat Wiring 50P030 100 Units Shown ...
Страница 135: ...135 Fig 24 Typical Power Wiring 115 V ...
Страница 136: ...136 Fig 25 Typical Gas Heat Section Size 030 050 Units Shown ...
Страница 138: ...138 Fig 27 Component Arrangement Size 030 035 Units ...
Страница 139: ...139 Fig 28 Component Arrangement Size 040 075 Units ...
Страница 140: ...140 Fig 29 Component Arrangement Size 090 100 Units ...
