Carrier 48/50AJ specifications Control will not attempt to learn MAT over time

MAT Calc Config (MAT.S) — This configuration gives the user two options in the processing of the mixed-air temperature (MAT) calculation:

•MAT.S = 0

There will be no MAT calculation.

•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 method, the control has an internal table whereby it can more closely determine the true MAT value.

•MAT.S = 2

The control will not attempt to learn MAT over time.

To calculate MAT linearly, the user should reset the MAT table entries by setting MAT.R to YES. Then set MAT.S = 2. The control will calculate MAT based on the position of the economizer and outside air and return air temperature.

To freeze the MAT table entries, let the unit run with MAT.S

=1. Once sufficient data has been collected, change MAT.S

=2. Do not reset the MAT table.

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 to limit or reduce cooling capacity during run time. The term Demand Limit Control re- fers to the restriction of machine capacity to control the amount of power that a machine will use. This can save the owner money by limiting peaks in the power supply. Demand limit control is intended to interface with an external Loadshed De- vice 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 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 63.

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 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 (0-100% 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:

Switch Status Run Status→COOL→DEM.L = 1

Inputs→GEN.I→DL.S1 = OFF 100%

Inputs→GEN.I→DL.S2 = OFF

Inputs→GEN.I→DL.S1= ON Configuration→DMD.L→D.L.S1

Inputs→GEN.I→DL.S2 = OFF

Inputs→GEN.I→DL.S1= ON Configuration→DMD.L→D.L.S2

Inputs→GEN.I→DL.S2 = ON

Inputs→GEN.I→DL.S1= OFF Configuration→DMD.L→D.L.S2

Inputs→GEN.I→DL.S2 = ON

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.Mvalue is used to determine 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 interpolation from 0% to “D.L.20”% based on the Inputs→ 4-20→DML.Minput 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.

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%

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.

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