52
MAT Calc Config (MAT.S) — This configuration gives the
user three options in the processing of the mixed-air tempera-
ture (MAT) calculation:
•MAT.S = 0
The control will not attempt to learn MAT over time. The
control will simply calculate MAT based on the position of
the economizer, outside and return air temperature, linearly.
•MAT.S = 1
The control will attempt to learn MAT over time. Any time
the system is in a vent mode and the economizer stays at a
particular position for long enough, MAT = EDT. Using
this, the control has an internal table whereby it can more
closely determine the true MAT value.
•MAT.S = 2
The control will stop learning and use whatever the control
has already learned. Using this setting infers that the control
has spent some time set to MAT.S = 1.
First set MAT.S = 1. Then go into the Service Test mode,
turn on the fan and open the economizer to a static position for
5 minutes. Move to several positions (20%,40%,60%,80%). It
is important that the difference between return and outside
temperature be greater than 5 degrees. (The greater the delta,
the better). When done, set MAT.S = 2 and the system has been
commissioned.
Reset MAT Table Entries? (MAT.R) — This configuration
allows the user to reset the internally stored MAT learned
configuration data back to the default values. The defaults are
set to a linear relationship between the economizer damper
position and OAT and RAT in the calculation of MAT.
SumZ Overrides — There are a number of overrides to the
SumZ algorithm which may add or subtract stages of cooling.
• High Temp Cap Override (H.TMP)
• Low Temp Cap Override (L.TMP)
• Pull Down Cap Override (PULL)
• Slow Change Cap Override (SLOW)
Economizer Trim Override — The unit may drop stages of
cooling when the economizer is performing free cooling and
the configuration Configuration
→
ECON
→
E.TRM is set to
Yes. The economizer controls to the same supply air set point
as mechanical cooling does for SumZ when E.TRM = Yes.
This allows for much tighter temperature control as well as cut-
ting down on the cycling of compressors.
For a long cooling session where the outside-air tempera-
ture may drop over time, there may be a point at which the
economizer 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 temperature set point below which mechanical cooling will
be completely locked out.
DEMAND LIMIT CONTROL — Demand Limit Control
may override the cooling algorithm and clamp or shed
cooling capacity during run time. The term Demand Limit
Control refers to the restriction of the machine capacity
to control the amount of power that a machine will use.
Demand limit control is intended to interface with an external
Loadshed Device either through CCN communications, exter-
nal 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 configura-
tion (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 41.
Demand Limit Select (DM.L.S) — This configuration deter-
mines the type of demand limiting.
• 0 = NONE — Demand Limiting not configured.
• 1 = 2 SWITCHES — This will enable switch input
demand limiting using the switch inputs connected to the
CEM board. Connections should be made to TB204
terminals 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 exter-
nally sourced controller and should be connected to
TB203 terminals 2 and 3.
• 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 (0-100% total capacity)
Demand Limit 2 Setpoint (D.L.S2) — Dmd Limit Switch
Setpoint 2 (0-100% total capacity)
The state of the discrete switch inputs can be found at the lo-
cal display:
Inputs
→
GEN.I
→
DL.S1
Inputs
→
GEN.I
→
DL.S2
The following table illustrates the demand limiting (Run
Status
→
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 limiting, then the
Inputs
→
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 correspond-
ing to a 20 mA input (0 to 100%).
The value of percentage reset is determined by a linear
interpolation 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.
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%