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45
Economizer Trim Override
The unit may drop stages of cooling when the economizer is per-
forming free cooling and the configuration
Configuration
ECON
E.TRM
is set to Yes. The economizer controls to the
same supply air setpoint as mechanical cooling does for SumZ
when
E.TRM
= Yes. This allows for much tighter temperature
control as well as cutting down on the cycling of compressors.
For a long cooling session where the outside-air temperature
may drop over time, there may be a point at which the econo-
mizer has closed down far enough were the unit could remove
a cooling stage and open up the economizer further to make up
the difference.
Mechanical Cooling Lockout (Configuration
COOL
MC.LO)
This configuration allows a configurable outside-air tempera-
ture setpoint below which mechanical cooling will be com-
pletely locked out.
DEMAND LIMIT CONTROL
Demand Limit Control may override the cooling algorithm to
limit or reduce cooling capacity during run time. The term De-
mand Limit Control refers to the restriction of machine capaci-
ty to control the amount of power that a machine will use. This
can save the owner money by limiting peaks in the power sup-
ply. Demand limit control is intended to interface with an ex-
ternal Loadshed Device either 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 setpoint 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 48.
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 TB6-4, 5, 6.
• 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 TB6-7, 8.
• 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 Set-
point 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 log-
ic 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 limiting, then the
In-
puts
4-20
DML.M
value is used to determine the amount
of demand limiting in effect (
Run Status
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 Load-
shed time
Table 48 — 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
Summary of Contents for WEATHERMAKER 48A2020
Page 112: ...112 Fig 20 Typical Main Control Box Wiring Schematic 48 50A Units ...
Page 113: ...113 Fig 21 Typical Auxiliary Control Box Wiring Schematic ...
Page 114: ...114 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown ...
Page 115: ...115 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown TO NEXT PAGE ...
Page 116: ...116 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont ...
Page 117: ...117 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown ...
Page 118: ...118 Fig 25 Typical Controls Option Wiring Schematic SW1 SW2 OR DEHUMIDIFY SWITCH ...
Page 119: ...119 Fig 26 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown ...
Page 120: ...120 Fig 27 Typical Power Schematic of Greenspeed Low Ambient Option 48 50A 060 Unit Shown ...
Page 121: ...121 Fig 28 Typical Small Chassis Component Location Size 020 035 Units ...
Page 122: ...122 Fig 29 Typical Large Chassis Component Locations Size 040 060 Units ...
Page 185: ...185 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716 ...