ADAPTM (Adaptive control, multiple) - User Guide - PXC4.E16.A - PXC5.E24.A - PXC7.E400.A

pv

Point name of the process variable being controlled.

This parameter is usually an LAI point, but it can be an LAO point or a local variable that represents supply air temperature.

This value should be between -50.0 and 150.0.

cv

Controlled variable (output signal). This signal is 0.0 to 100.0 percent, direct acting, and is intended to go to TABLE statements–one for each output actuator point (for example, heating, dampers and cooling).

-   This parameter can be a point name or local variable.

sp

Setpoint for the loop against which the process variable is compared.

-    This parameter can be a point name, local variable name, or decimal number.

-   This value must be between -50.0 and 150.0, and should be in the same engineering units as pv.

matcl

Represents the output of the mixed air temperature control loop (usually an ADAPTS loop). When the value of matctl is equal to or drops below the value of mam, the cv output will not rise above the her value.

-   This parameter can be a point name, local variable name, or decimal number.

-   This value must be between 0.0 and 100.0.

-   For applications without dampers or without mixed air temperature override of the dampers, set matctl to 100.0.

mam

Mixed air damper minimum position.

-  This parameter can be a point name, local variable name, or decimal number.

-  This value must be between 0.0 and 100.0.

For applications without dampers (heating and cooling only), set mam to 0.0.

st

Sample time (in seconds). This is the time, in seconds, between two successive starts of execution of the ADAPTM algorithm. It is also the time interval between two samples of data by ADAPTM.

-   This parameter can be an integer, point name, or local variable name.

-   The minimum sample time allowed is 1 second.

- For a system with smaller size coils, typically set st to 5 seconds.

- For a system with larger size coils, typically set st to 10 seconds.

- The Sample Time must be less than or equal to one-third of the smallest Time Constant. That is,  

Where:

st is the Sample Time, and

tc is the smallest of tcd, tch, and tcc.

kc

Control gain.

-  This parameter can be a point name, local variable name, or decimal number.

-  This value must be greater than 0.0.

-  For English units set kc to 3.0. For SI Units set kc to 6.0.

tcd

Damper time constant (in seconds).

- This parameter can be a point name, local variable name, or decimal number.

- This value must be greater than or equal to 3 times the st value.

- For applications with heating and cooling only (no dampers), set tcd to the value of tcc.

The damper time constant is, itself, very small in value–typically equal to that of the supply air temperature sensor and the damper actuator stroke time. However, since the air from the dampers must go through the coil(s) before reaching the supply air temperature sensor, the coil(s) time constant(s) (minus their actuator times and the supply air temperature sensor's time constant) must be added to the damper time constant.

The ADAPTM damper time constant parameter entry (in seconds) is calculated using this formula:

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Where:

tcd = ADAPTM damper time constant parameter entry (in seconds)

T downstream coils = time constants of coils alone downstream of dampers (between the dampers and the duct temperature sensor).

T sensor = time constant of the supply air sensor (usually about 30 seconds)

T damper actuator = stroke time of the damper actuator (often 30 seconds)

tch

Heating time constant (seconds).

- This parameter can be a point name, local variable name, or decimal number.

- This value must be greater than or equal to 3 times the st value.

- For applications with dampers and cooling only (no heating), set tch to the value of tcd.

The time constant of the heating coil alone is calculated using the following formula:

Where:

CFMmax = Maximum or design airflow rate in cubic feet per minute

GPMmax = Maximum or design hot water flow rate in gallons per minute

l/s air max = Maximum or design air flow rate in liters per second

l/s hot water max = Maximum or design hot water flow rate in liters per second

The ADAPTM heating time constant parameter entry (in seconds) is calculated using this formula:

Where:

tch = ADAPTM heating time constant parameter (in seconds).

T downstream coils = time constants of other coils alone downstream of heating coil (between heating coil and duct temperature sensor).

T sensor = time constant of the supply air sensor (usually about 30 seconds).

T hc actuator = stroke time of the heating coil actuator (often 30 seconds).

tcc

Cooling time constant (in seconds).

- This parameter can be a point name, local variable name, or decimal number.

- This value must be greater than or equal to 3 times the st value.

- For applications with heating and dampers only (no cooling coil), set tcc to the value of tcd.

The time constant of the cooling coil alone is calculated using the following formula:

Where:

CFMmax = Maximum or design airflow rate in cubic feet per minute

GPMmax = Maximum or design chilled water flow rate in gallons per minute

L/s air max = Maximum or design air flow rate in liters per second

L/s chilled water max = Maximum or design chilled water flow rate in liters per second

The ADAPTM cooling time constant parameter entry (in seconds) is calculated using this formula:

Where:

tcc = ADAPTM cooling time constant parameter (in seconds)

Tdownstream coils = time constants of coils alone downstream of cooling coil (between

cooling coil and duct temperature sensor)

Tsensor = time constant of the supply air sensor (often 30 seconds)

tcc actuator = stroke time of the cooling coil actuator (often 30 seconds)

her

Heating end of range (in percent). This parameter tells ADAPTM what percentage of its output is used for heating. It is assumed that the beginning of the heating range is at 0%.

- This parameter can be a point name, local variable name, or decimal number.

- This value must be:

        - Equal to or greater than 0, and

        -  Less than or equal to dbr.

- For applications with dampers and cooling only (no heating), set her to 0.

The following figure shows the relationship of her to the operation of the heating, dampers and cooling outputs.

Typically, the value for her will be the same as the second to the last parameter for the TABLE statement controlling the heating coil. For example, as shown in the line of code below, this value is 45.

05030  TABLE (%X%VRT,%X%HCO,0,100,45,0)

If the value of her varies slightly due to the path taken in the code, choose a nominal value for her. ADAPTM can handle minor variations in the value of her.

dbr

Damper beginning of range. This parameter, along with the Damper End of Range (der), tells ADAPTM what percentage of its output is used for mixed air damper control (free cooling).

- This parameter can be a point name, local variable name, or decimal number.

-  This value must be:

        -  Greater than or equal to her, and

      -   Less than der.

- For applications with heating and cooling only (no dampers), set dbr to the value of der.

- For applications with dampers and cooling only (no heating), set dbr to 0.

The following figure shows the relationship of dbr to the operation of the heating, dampers and cooling outputs.

Typically, the value for dbr will be the same as the third parameter for the TABLE statement controlling the mixed air damper. For example, as shown below in the line of code below, this value is 50.

5050  TABLE (%X%VRT,$MADCTL,50,%X%MAM,65,100)

If other PPCL code is used, dbr must still be the value of the output of ADAPTM at which mixed air dampers begin to open from minimum position.

If the value of dbr varies slightly due to the path taken in the code, choose a nominal value for dbr. ADAPTM can handle minor variations in the value of dbr.

der

Damper end of range. This parameter, along with the Damper Beginning of Range (dbr), tells ADAPTM what percentage of its output is used for mixed air damper control (free cooling). Damper End of Range also tells ADAPTM what percentage of its output is used for cooling since der defines the beginning of the cooling coil range.

-   This parameter can be a point name, local variable name, or decimal number.

-  This value must be:

      -  Greater than or equal to dbr, and

        - Less than or equal to 100.

-  For applications with heating and dampers only (no cooling), set der to 100.

-  For applications with heating and cooling only (no dampers), set der to the value of dbr.

-  The end of the cooling range is assumed to be at the adaptive control output of 100%.

The following figure shows the relationship of der to the operation of the heating, dampers (for cooling), and cooling coil outputs.

Typically, the value for der will be the same as the third parameter for the TABLE statement controlling the cooling coil.

If there are two cooling coil TABLE statements because there is an Economizer, choose the one for Economizer ON. For example, as shown in the line of code below, this value is 65.

2060  TABLE (%X%VRT,%X%CCO,65,0,100,100)

If other PPCL code is used, der must still be the value of the output of ADAPTM at which mixed air dampers are fully open and the cooling coil valve is just beginning to open.

If the value of der varies slightly due to the path taken in the code, choose a nominal value for der. ADAPTM can handle minor variations in the value of der.

err

Error reporting point. ADAPTM writes to this point. A zero means no error. A non-zero means an error.

- This parameter is entered as a point name or local variable name.