Direct Digital Control

TAC Pacific Technical Training

Course: 2003AP TAC I/NET Seven BMS Programming

Reference Manual Section 3 – Direct Digital Control

DIRECT DIGITAL CONTROL

TAC BMS REFERENCE MANUAL Revision 1.0.0

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CONTENTS

Page


3-3

INPUT and OUTPUTs

3-4

DDC MODULES

3-6 Two Position

3-7

PID

3 - 10

Floating

3 - 17

Reset

3 - 23

HiLo

3 - 26

Relay

3 - 28

Air Handling Unit

3 - 31

Fan Coil Unit

3 - 36

DDC APPLICATIONS

MICRO REGULATORS

3 – 40 Configuration

3 - 40

MR Parameters

3 - 42

I/STAT LED Functions

3 - 45

STR-250 Functions

3 - 47

Hardware Coefficients

3 - 49

Stand Alone ATS

3 - 52

Direct Digital Control

3 - 54

Micro Regulator Editors

3 - 57


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Direct Digital Contro l R e f e r e n c e : I/NET SEVEN, System Operator Guide, “Direct Digital

Control”. I/NET SEVEN, Technical Reference Guide “Direct Digital Control”.

I/NET offers you microprocessor based Direct Digital Control (DDC). This control program measures a variable, compares the measured variable against a desired value to determine an error, processes the error according to a specific software algorithm, and produces an output that modifies the controlled variable.

DDC is many things. It may be something as simple as measuring an input temperature, comparing the temperature against the defined set point, determining the difference between the input and the set point temperatures, and determining if that difference is positive or negative. The system then issues the appropriate command to bring the input temperature in line with the set point.

DDC also operates at a more complex level. It can take into consideration such factors as the magnitude of an error change since the last time the point was sampled. It can also determine the speed at which the error is increasing or decreasing and make corrections as appropriate. This is an example of proportional, integral, and derivative (PID) control. PID is just one of the module types available with I/NET.

There is an unfortunate tendency to interchange the terms DDC and PID. The two are not synonymous. All electronic PID control is DDC; however, not all DDC is PID control.

I/NET gives you a powerful, yet easy-to-use, DDC system. I/NET DDC emulates pneumatic control devices using an on-line module editor. You don’t need to be a technical wizard to use DDC and you don’t need any special training or retraining before you add or modify your DDC control strategy.


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Inpu t and Output Design ations DDC module inputs are referred to as set points or process variables. Outputs are referred to as control outputs. I/NET requires that all DDC inputs be defined as points, lines, or constants. Outputs can be defined as either lines or points.

Points Points can be used as inputs to DDC modules when the input is the result of a calculation (internal point), the state/value sensed by an external point, or the state/value of a point controlled by the operator. Points can also receive module output when you want an action to occur as the result of a DDC module algorithm. Define module inputs and outputs as points by entering either the point name or the point address.

Lines It is often desirable, or necessary, to chain several DDC modules together in a cascade of control. This requires some way of making the output of one module available to other modules. This is accomplished with “lines.” These lines can transmit analogue or discrete data. Lines are equivalent to pneumatic tubing interconnecting pneumatic control devices and generally follow the same rules: •

Only one module should output to a specific line number. When possible, assign the same number to a module and the line to which it is delivering its output. This eliminates confusion as to which line belongs with which module and vice versa.

•

On the other hand, a specific line can act as an input to as many modules as is necessary.

N o t e : The HiLo and Floating module types have two outputs.

When you assign a line number to the first output of one of these modules, we recommend that you leave the next available DDC module number blank thus allowing you to use it's number if and when you add the second output to avoid future confusion.


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Constants Constants are values or state conditions that never change. They remain constant. You can enter a constant as a value (22 degrees) or a state (0 or 1). A constant may be used as a DDC module input; however, a constant may not be used as an output of a module. A constant output from a DDC module would make the module unnecessary.

THIS POINT REFLECTS THE TIME SCHEDULE POINT. CALCULATION 0000 AI RETURN AIR TEMP

0001 DI AHU ENABLE

1000 AO AHU SETPOINT

ON = LOGIC '1'

1 AHU ON 10 Secs

110

2 AHU H/C 8%=4Deg 300 0 DIRECT

0 - 100

3 HEATING 0 - 45% 100 - 0%

3100 AO AHU HEAT VALVE

4 COOLING 55 - 100% 0 - 100%

0 - 100 %


3101 AO AHU COOL VALVE

0 - 100 %

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DDC Modules I/NET carries out direct digital control through a series of modules. Module parameters are explained later in this document. Each module has its own algorithm. With a basic understanding of control theory and application, these algorithms are easy to understand and apply. Technically, there are seven types of DDC modules; however, no onecontroller type provides all seven module types. The seven DDC module types are: Two-position PID Floating Reset

HiLo (not available in MRs) Relay Calculation (MRs only)

The DCUs and PCUs provide all but the Calculation module. Micro Regulator (MR) controllers provide all but the HiLo module. Application Specific Controllers (ASCs) provide all but the HiLo Module. UCs provides variations of the PID and Floating modules. Each module type has its own data entry screen where you define parameters such as inputs, algorithm modifiers, and output destinations. These data entry screens are described in the I/NET System, System Operator Guide, “Direct Digital Control".


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Two-Position Module (2-Pos) The Two-position module is similar to an electric thermostat but responds much more precisely and predictably. This module compares input and set point values and provides an ON/OFF output signal to a DO/DC point or line. This type of control is commonly used for simple heating or cooling systems, starting and stopping motors, controlling water sprays for humidification, etc. The parameters for the Two-position module are listed below.

Module Name A name used to describe the module. This name can be up to eight alphanumeric characters. Sample Interval (sec) A number between 1 and 255 that represents the number of seconds between module outputs. Set point The desired value of the input point being controlled. Typically this is the desired room temperature or something similar. A line, point, or constant may represent it.


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DIRECT DIGITAL CONTROL Two-Position Module (2-Pos) Set point Offset You may want to utilise set point offset if you have defined your set point as a line or point. Set point offsets are useful when you want “cascaded” control. That is, you have several modules that share a common set point (line or point) which need to be staggered in their operating range. Input (process variable) The input for the module. The point, line, or constant that represents the value of the process being controlled (air temperature, water pressure, etc.). Input Filter This option lets you average up to five previous input values with the current input value to reduce the impact of rapidly changing inputs. All DCUs/PCUs and MRs use a Yes or No setting, rather than a value, for the input filter parameter. These devices automatically average the last five inputs with the current input if their input filter parameter is set to Yes. Input Low Limit This parameter defines the lower limit of the set point (not the process variable input). The module declares the set point no longer valid if the set point value drops below the input low limit. If the set point drops below the input low limit, the module immediately declares a “bad input” and, depending on the applicable module, the following action occurs: • The Two-position module outputs the fail-safe Command State (Off or On, see Fail-safe Command below). Input High Limit This parameter defines the upper limit of the set point (not the process variable input). The module declares the set point no longer valid if the set point value rises above the input high limit. If the set point value exceeds the input high limit, the module immediately declares a “bad input” and, depending on the applicable module, the following action occurs: • The Two-position module outputs the fail-safe Command State (Off or On, see Fail-safe Command below). Output You can direct the output of the module to a line or point. Select a line if the output is used by another DDC module. Select a point if the output is used to initiate an event sequence, to provide intermediate control, or to directly control an action.


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DIRECT DIGITAL CONTROL Two-Position Module (2-Pos) Fail-safe Command The action executed when the input or set point is no longer valid. Use this option to plan system response to a set point or sensor failure. Acceptable settings are Off or On. Note:

W h e n s e le c t in g " O f f " t h e 2 p o s i t io n m o d u l e w i ll o u t p u t a l o g i c " 0 " w h e n f a i l - s a f e is a c t i v a t e d . W h e n s e le c t in g " O n " t h e 2 p o s i t io n m o d u l e w i ll o u t p u t a l o g i c " 1 " w h e n f a i l - s a f e is a c t i v a t e d .

The fail-safe command is executed if the set point exceeds the input high or input low limits or if the process variable input exceeds its sensor limits as defined in the resident I/O points editor. Differential The degree of precision for this module. Differential is the range of process variable that causes the output to switch from 'On' to 'Off'. Mode The mode you select determines what happens when the input is higher or lower than the set point. • Direct: The two position module issues a logic '0' command to the output point or line if the input rises above the set point plus one half the differential. The module issues a logic '1' command to the output point or line if the input falls below the set point minus one half the differential. • Reverse: The two position module issues a logic '1' command to the output point or line if the input rises above the set point plus one half the differential. The module issues a logic '0' command to the output point or line if the input falls below the set point minus one half the differential.


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DIRECT DIGITAL CONTROL Proportional, Integral, Derivative Module (PID)

The term’s proportional, integral and derivative describe the output response of a module based on a varying set of conditions occurring by the process variable. Each of the three elements of PID has a distinctive purpose:

Proportional: This element can best be described as coarse control, which provides a rapid response to an error (i.e., the difference between the set point and the process variable). All proportional control has an inherent flaw called “offset”, which simply means that it will always control at a point above or below set point.

Integral: The integral element of PID can best as fine tuning proportional control. It produces an effect that is designed to reduce the “offset” (inherent to proportional control) to zero.

Derivative: A lead adjustment which produces an output preceding the proportional output based on the rate of change in the error signal. Derivative control reduces upsets due to sudden load changes, which rarely occur in air conditioning control.

The PID module is commonly used for the control valves, vanes or modulating motors where an analogue is used. This module compares the current input and set point to determine the current error. Proportional, Integral, and Derivative corrections to an analogue output point can then be made depending on the magnitude and direction of this “error”. The parameters for the PID module are listed below.


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DIRECT DIGITAL CONTROL Proportional, Integral, Derivative Module (PID)

Module Name A name used to describe the module. This name can be up to eight alphanumeric characters. Sample Interval (sec) A number between 1 and 255 that represents the number of seconds between module outputs. Set point The desired value of the input point being controlled. Typically this is the desired room temperature or something similar. A line, point, or constant may represent it. Set point Offset You may want to utilise set point offset if you have defined your set point as a line or point. Set point offsets are useful when you want “cascaded” control. That is, you have several modules that share a common set point (line or point) which need to be staggered in their operating range.


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DIRECT DIGITAL CONTROL Proportional, Integral, Derivative Module (PID) Input (process variable) The input for the module. The point, line, or constant that represents the value of the process being controlled (air temperature, water pressure, etc.). Input Filter This option lets you average up to five previous input values with the current input value to reduce the impact of rapidly changing inputs. All DCUs/PCUs and MRs use a Yes or No setting, rather than a value, for the input filter parameter. These devices automatically average the last five inputs with the current input if their input filter parameter is set to Yes. Input Low Limit This parameter has two (2) functions. In the first function this parameter defines the lower limit of the module’s set point (not the process variable input). The module declares the set point no longer valid if the set point value drops below the input low limit. If the set point drops below the input low limit, the module immediately declares a “bad input” and, depending on the applicable module, the following action occurs: •

The PID module outputs the control point value, unless operating in P only mode. In P only mode, the PID module clamps the output to either the output high limit or the output low limit, depending on the actuator mode setting.

The Input Low Limit’s second function defines the PID’s Input Low Limit when calculating Proportional Band (PB). See “Proportional Band” page 3 - 13. Input High Limit This parameter has two (2) functions. In the first function this parameter defines the upper limit of the module’s set point (not the process variable input). The module declares the set point no longer valid if the set point value rises above the input high limit. If the set point value exceeds the input high limit, the module immediately declares a “bad input” and, depending on the applicable module, one of the following actions occur: •

The PID module outputs the control point value, unless operating in P only mode. In P-only mode, the PID module clamps the output to either the output high limit or the output low limit, depending on the actuator mode setting.


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DIRECT DIGITAL CONTROL Proportional, Integral, Derivative Module (PID) The Input High Limit’s second function defines the PID’s Input High Limit when calculating Proportional Band (PB). See “Proportional Band” page 3 - 13. Output You can direct the output of the module to a line or point. Select a line if the output is used by another DDC module. Select a point if the output is used to initiate an event sequence, to provide intermediate control, or to directly control an action. Output Ramp Limit (percent) The output ramp limit is a value (percent) between 0 and 100 used to define the magnitude of the largest change in output you want the system to issue between samples. Output Low Limit The output low limit defines the minimum output value. The default is zero because the output of the module is typically in percent. For example, you could use this parameter to limit travel in a valve or damper actuator. Output High Limit The output high limit defines the maximum output value. The default is 100 because the module output is typically in percent. For example, you could use this parameter to limit travel in a valve or damper actuator. Control Point (Fail-safe) This is a number between 0 and 100 percent. The default is 50 percent. This parameter value is output from the PID module under the following conditions: • The process variable is the same as the set point, P-only Mode of Operation. • The set point exceeds the module’s input high or low limit parameters. • The input point (input to the module) exceeds its sensor high or low limit you specified when you defined the AI point in the Resident I/O editor. Proportional Band (percent) In DCUs and PCUs, this is the percent of the input range (the range between the module’s Input High Limit and Input Low Limit) that the input value must change in order to change the output from zero to 100 percent.


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DIRECT DIGITAL CONTROL Proportional, Integral, Derivative Module (PID) In DCUs and PCUs, proportional band is defined by the following equation: Proportional Band in engineering units (°C) x 100 Range between the high and low sensor limits 1 Reset Interval (seconds) Use this function to eliminate a persistent error that is not of sufficient magnitude (as measured at the specified sample interval) to create a change in the output. This error called “offset. Actuator Mode This parameter defines the response of the PID module. • Direct: If you select this mode, the PID module increases its output if the input rises. The PID module decreases its output value if the input falls. • Reverse: If you select this mode, the PID module decreases its output if the input rises. The PID module increases its output value if the input falls. Rate Interval (seconds) This is the rate portion of the PID or Floating module algorithm. Enter a number between 0 and 3,600 for the rate interval. The default is zero seconds. Use this function to compensate for large input changes by comparing the dire ction and magnitude of the error between samples and correcting the output accordingly. Adaptive Control This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. This parameter defines the point address or name of the discrete point that will be used to enable/disable adaptive control. Adaptive control is enabled/disabled by the state of the specified discrete point (disabled = 0 and enabled = 1). Maximum Bump (percent) This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. A number between 0 and 100 percent. The default is 5 percent. This parameter determines the size of the PID or Floating output step change for automatic tuning in reference to the module control point (PID) or mid-scale position (Float). The bump should be large enough to cause a change in the input (process variable) that is greater than the noise band, but not so large as to damage the controlled equipment. The typical range is 5 to 25 percent.


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DIRECT DIGITAL CONTROL Proportional, Integral, Derivative Module (PID) Settling Time (seconds) This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. The settling time can be between 10 and 1,800 seconds. The default is 120 seconds. This parameter is an estimate of the time it takes for the input (process variable) to settle down after a set point change. It is used for automatic and adaptive tuning as the minimum time interval between a process disturbance and the next action. For automatic tuning, it is the time interval between setting the output to either the control point (PID) or to mid-scale (Floating) and the beginning of the tuning cycle. For adaptive tuning, it is the minimum time that will be observed between parameter calculations. You can best estimate the settling time by observing the input settling time after a natural process disturbance. To do this, you measure the time interval from the point of the disturbance to a point where the effects of the disturbance are negligible. The typical range is between 30 and 150 seconds.

Maximum Overshoot (percent) This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. This parameter is a number between 0 and 100 percent. The default is 10 percent. This parameter, along with target damping (described below), controls the shape of the initial output response to a process disturbance. The magnitude of the module response is a qualitative measure of the controller. The typical range for this parameter is between 10 and 50 percent.

Target Damping (percent) This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. Target damping can be set to a value between 1 and 75 percent. This parameter represents the desired reduction in the process variable overshoot from the first overshoot (maximum overshoot) to the second, and so on. A value of 25 percent means the second over-shoot magnitude should be 25 percent of the first. The recommended value for this parameter is the default: 25.


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DIRECT DIGITAL CONTROL Proportional, Integral, Derivative Module (PID) Noise Band (percent) This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. Noise band can be set to a value between 0 and 100 percent. The default is 2 percent. This parameter, specified as a percentage of the input range, is the minimum process variable change that initiates an adaptive calculation of the module parameters (provided the Adaptive Control discrete point described above is equal to one). Because adaptive tuning attempts to reshape the process variable response after every such change, it is important to make the noise band big enough to prevent inadvertent unnecessary tuning. The typical range is between 2 and 10 percent.


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DIRECT DIGITAL CONTROL Floating Module (FLOAT) The Floating module operates much like the PID module, described above. The operation of the algorithm is the same and the entries, which modify the proportional band, reset interval, and rate interval, are identical. The difference between the two modules lies in the outputs to the final control element. The PID module has inherent positional feedback (i.e., the module always “knows where the output is”). The output of the PID module is always a percentage of the full-scale full-scale output. The output of the Floating module is directed to two separate DO points as an increase command and a decrease command. The module does not know the exact position of the controlled valve or damper and assumes that the controlled device was driven to the correct position. You need this module and its outputs when a bi-directional motor controls the final control element (valve, damper, etc.). The parameters for the Floating module are listed below.


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DIRECT DIGITAL CONTROL Floating Module (FLOAT) Module Name A name used to describe the module. This name can be up to eight alphanumeric characters. Sample Interval (sec) A number between 1 and 255 that represents the number of seconds between module outputs. Set point The desired value of the input point being controlled. Typically this is the desired room temperature or something similar. A line, point, or constant may represent it. Set point Offset You may want to utilise set point offset if you have defined your set point as as a line or point. Set point offsets offsets are useful when you want “cascaded” “cascaded” control. That is, you have several several modules that share a common set point (line or point) which need to be staggered in their operating range. Input (process variable) The input for the module. The point, line, or constant that represents the value of the process being controlled (air temperature, water pressure, etc.). Input Filter This option lets you average up to five previous input values with the current input value to reduce the impact of rapidly changing inputs. All DCUs/PCUs DCUs/PCUs and MRs use a Yes Yes or No setting, rather than a value, for the input filter filter parameter. parameter. These devices devices automatically average the last five inputs with the current input if their input filter parameter is set to Yes. Yes. Input Low Limit This parameter has two (2) functions. functions. In the first function this parameter defines the lower limit of the module’s set point (not the process variable input). The module declares the set point no longer valid if the set point value drops below the input low limit. If the set point drops below the input low limit, the module immediately declares a “bad input” and, depending on the applicable module, the following action occurs: The Floating module stops any pulse outputs. The Input Low Limit’s second function defines the PID’s Input Low Limit when calculating Proportional Band (PB). See “Proportional “Proportional Band” Band” page 3 - 19.


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DIRECT DIGITAL CONTROL Floating Module (FLOAT) Input High Limit This parameter has two (2) functions. In the first function this parameter defines the upper limit of the module’s set point (not the process variable input). The module declares the set point no longer valid if the set point value rises above the input high limit. If the set point value exceeds the input high limit, the module immediately declares a “bad input” and, depending on the applicable module, one of the following actions occur: • The Floating module stops any pulse outputs. The Input High Limit’s second function defines the PID’s Input High Limit when calculating Proportional Band (PB). See “Proportional Band” page 3 - 19. Output (Increase) In a DCU or PCU, you may use a line or a DO point for this parameter. In a MR or ASC, only a DO point (not a line) can be used as the output. In the UC, the user simply enters the hardware bit (0– 7) to be controlled by the UC Floating extension. The Floating module issues timed pulse outputs to rotate a bidirectional motor. This parameter directs a timed pulse to increase the output. This results in a specific action, such as the opening of a valve. Output (Decrease) In a DCU or PCU, you may use a line or a DO point for this parameter. In a MR or ASC, only a DO point (not a line) can be used as the output. In the UC, the user simply enters the hardware bit (0– 7) to be controlled by the UC Floating extension. This parameter reverses the activity instigated by the output increase, described above. For example, if the increase pulse opens a valve, the decrease pulse closes a valve. Throttling Range (seconds) This parameter defines the number of seconds it takes for the actuator to move from being fully open to fully closed and vice versa. This time becomes the maximum increase/decrease pulse duration time. For the Floating module, enter a number between 0 and 255. The default is zero.


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DIRECT DIGITAL CONTROL Floating Module (FLOAT) Turn-Around (seconds) This parameter defines the number of seconds it takes to complete a reversal in the bi-directional motor rotation (i.e., changing from clockwise to counter-clockwise or visa versa). Enter a number between 0 and 255 for this parameter. The default is zero. Note: Most actuator manufacturers do not give this parameter within the actuators technical data. A setting of 0 seconds could be used. Proportional Band (percent) In DCUs and PCUs, this is the percent of the input range (the range between the module’s Input High Limit and Input Low Limit) that the input value must change in order to change the output from zero to 100 percent. In DCUs and PCUs, proportional band is defined by the following equation: Proportional Band in engineering units (°C) x 100 Range between the high and low sensor limits 1 Reset Interval (seconds) Use this function to eliminate a persistent error that is not of sufficient magnitude (as measured at the specified sample interval) to create a change in the output. This error called “offset. This is the rate portion of the PID or Floating module algorithm. Enter a number between 0 and 3,600 for the rate interval. The default is zero seconds. Use this function to compensate for large input changes by comparing the direction and magnitude of the error between samples and correcting the output accordingly. Actuator Mode This parameter defines the response of the PID or Floating module. • Direct: If you select this mode, Floating module issues an increase pulse if the input rises. The Floating module issues a decrease pulse if the input falls. • Reverse: If you select this mode, the Floating module issues a decrease pulse if the input rises. The Floating module issues an increase pulse if the input falls. Adaptive Control This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. This parameter defines the point address or name of the discrete point that will be used to enable/disable adaptive control. Adaptive control is enabled/disabled by the state of the specified discrete point (disabled = 0 and enabled = 1).


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DIRECT DIGITAL CONTROL Floating Module (FLOAT) Maximum Bump (percent) This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. A number between 0 and 100 percent. The default is 5 percent. This parameter determines the size of the PID or Floating output step change for automatic tuning in reference to the module control point (PID) or mid-scale position (Float). The bump should be large enough to cause a change in the input (process variable) that is greater than the noise band, but not so large as to damage the controlled equipment. The typical range is 5 to 25 percent. Settling Time (seconds) This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. The settling time can be between 10 and 1,800 seconds. The default is 120 seconds. This parameter is an estimate of the time it takes for the input (process variable) to settle down after a set point change. It is used for automatic and adaptive tuning as the minimum time interval between a process disturbance and the next action. For automatic tuning, it is the time interval between setting the output to either the control point (PID) or to mid-scale (Floating) and the beginning of the tuning cycle. For adaptive tuning, it is the minimum time that will be observed between parameter calculations. You can best estimate the settling time by observing the input settling time after a natural process disturbance. To do this, you measure the time interval from the point of the disturbance to a point where the effects of the disturbance are negligible. The typical range is between 30 and 150 seconds. Maximum Overshoot (percent) This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. This parameter is a number between 0 and 100 percent. The default is 10 percent. This parameter, along with target damping (described below), controls the shape of the initial output response to a process disturbance. The magnitude of the module response is a qualitative measure of the controller. The typical range for this parameter is Target Damping (percent) This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs between 10 and 50 percent. Target damping can be set to a value between 1 and 75 percent.


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DIRECT DIGITAL CONTROL Floating Module (FLOAT) This parameter represents the desired reduction in the process variable overshoot from the first overshoot (maximum overshoot) to the second, and so on. A value of 25 percent means the second over-shoot magnitude should be 25 percent of the first. The recommended value for this parameter is the default: 25. Noise Band (percent) This tuning parameter is available in the PID and Floating modules of DCUs and PCUs; it is not available in MRs, UCs, and ASCs. Noise band can be set to a value between 0 and 100 percent. The default is 2 percent. This parameter, specified as a percentage of the input range, is the minimum process variable change that initiates an adaptive calculation of the module parameters (provided the Adaptive Control discrete point described above is equal to one). Because adaptive tuning attempts to reshape the process variable response after every such change, it is important to make the noise band big enough to prevent inadvertent unnecessary tuning. The typical range is between 2 and 10 percent.


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DIRECT DIGITAL CONTROL Reset Module (RESET) The reset module produces a primary reset schedule and modifies the results of that schedule based upon a secondary input. The output of this module typically provides a set point to another module and generally does not directly control an output point. The Reset module is typically used to reset the set point of a controlling module (Twoposition, PID, Floating) based on one or two measured inputs. This increases the rate of space temperature modification but does not improve control capability. This reset function is probably familiar to control engineers as the technique used to reset the set point of a boiler according to outside air temperature. As the outside temperature drops, the temperature of the water must increase to maintain the desired temperature in the spaces served by the boiler (the heating load increases). The two temperatures are inversely proportional to each other. This function has been used for decades in pneumatic control systems and is a valid concept. Reset control is also used to reset the discharge temperature of an HVAC unit based on the space temperature. The parameters for the Reset module are listed below

Module Name A name used to describe the module. This name can be up to eight alphanumeric characters.


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DIRECT DIGITAL CONTROL Reset Module (RESET) Sample Interval (sec) A number between 1 and 255 that represents the number of seconds between module outputs. Primary Input Select a line, point, or constant for this parameter. It can also be a line that is output from another module, or a constant. In a MR or ASC resident module, only a line or point can be specified a constant cannot be used. Primary Inputs 1 and 2 These input values, in engineering units of the primary sensed variable, are the major factor in determining the primary output. These entries are the minimum and maximum values over which we wish to reset the primary output. Primary Outputs 1 and 2 These two values define the module output in conjunction with the primary inputs. These entries determine the minimum and maximum outputs at the primary input values. N o t e : At primary input 1, the module outputs the value entered as

primary output 1; the same occurs with primary input 2 and primary output 2. This lets you define either a directly proportional reset schedule or an inversely proportional reset schedule. Secondary Input Select a line, point, or constant for this parameter. This input secondarily resets the output from the module. In a MR- or ASC-resident module, only a line or point can be specified a constant cannot be used. Secondary Inputs 1 and 2 These input values, in engineering units of the secondary measured variable, provide a second modifier for the module output. Secondary Outputs 1 and 2 These output values, in engineering units of the controlled variable, offset the set point derived by the primary input/output schedule. In short the resultant of the secondary function is added to the resultant of the primary function and then sent to the output. N O TE:

W hen using both the prim ary input and the input, the resultant of the prim ary and s ch e d u l e s a r e ' ad d e d ' a n d s e n t t o t h e o u t p u t .


s e co n d a r y s e co n d a r y

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DIRECT DIGITAL CONTROL Reset Module (RESET) Output You can direct the output of the module to a line or point. Select a line if the output is used by another DDC module. Select a point if the output is used to initiate an event sequence, to provide intermediate control, or to directly control an action.

Output Low Limit The output low limit defines the minimum output value. The default is zero because the output of the module is typically in percent. For example, you could use this parameter to limit travel in a valve or damper actuator. Output High Limit The output high limit defines the maximum output value. The default is 100 because the module output is typically in percent. For example, you could use this parameter to limit travel in a valve or damper actuator.


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DIRECT DIGITAL CONTROL HiLo Module (HiLo) The HiLo module provides a convenient means to extract the highest and/or lowest discrete state or value from among several discrete states or values. You can also accomplish this with the High and Low Operator calculations in the DCU/PCU. This module is not available in MRs or ASCs; instead the Calculation module can be used. The HiLo module will deselect any point that is in “old data” and happily process the remaining valid inputs. The High or Low functions within the calculation editor will not deselect any point that is in “old data”.

Note:

The HiLo module is commonly used to derive the highest space temperature needed to reset an air handling unit (AHU) cold deck discharge set point, and to select the lowest space temperature needed to reset an AHU hot deck discharge set point. The module is capable of providing both the high signal output and the low signal output simultaneously, if desired, making it unnecessary to use an additional module. The parameters for the HiLo module are listed below.



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DIRECT DIGITAL CONTROL HiLo Module (HiLo) Sample Interval (sec) A number between 1 and 255 that represents the number of seconds between module outputs. Input #1 - 4 A line, point, or constant. Each of the four inputs is normally the same type (analogue or discrete). Mixing of discrete states and analogue values is typically not done. Low Signal Out This parameter directs the minimum output value or logic level to either a line or a point. The HiLo module is capable of providing the high signal output and low signal output simultaneously. High Signal Out This parameter directs the maximum output value or logic level to either a line or a point. The HiLo module is capable of providing the high signal output and low signal output simultaneously.


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DIRECT DIGITAL CONTROL Relay Module (RELAY) The Relay module performs multiple functions as part of overall I/NET DDC capabilities. As you become more familiar with I/NET you will discover many uses for the Relay module. In its simplest form, this module is similar to a single-pole doublethrow relay. It has an input which acts as a coil (DI Select), a normally closed port (DI = 0 input), a normally open port (DI = 1 input), and a common Output. When used as a traditional relay, the module passes the state/value from the DI = 0 port to the common output when the DI Select (coil) value is 0. When the DI Select (coil) is 1, the module passes the state/value of the DI = 1 port to the output. This module can also function as an interval time delay relay (INT), as a delay-before-break relay (DBB), or as a delay-before-make relay (DBM). The parameters for the Relay module are listed



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DIRECT DIGITAL CONTROL Relay Module (RELAY) Sample Interval (sec) A number between 1 and 255 that represents the number of seconds between module outputs. DI Select This input can be a line or a point. If you select a point you must use a DO, DI, DC, or DA point type. If you select a line it must carry a discrete state (0 or 1) rather than an analogue value. This parameter is comparable to a relay coil. If the state of the line or point entered here is a 1, the relay module is “energised” and the module passes the state/value entering at the DI = 1 port. When the Relay module is “deenergised”, the DI = 0 state/value is passed to the module output. DI = 0 Input This is the state/value passed to the output by the Relay module when the discrete input (see above) is 0. Select a line, point, or a constant. DI = 1 Input This is the state/value passed to the output by the Relay module when the discrete input (see above) is 1. Select a line, point, or a constant. Time Delay (seconds) This parameter defines the number of seconds for the interval timer, delay-before-break, and delay-before-make relays. Enter a number between 0 and 86,400 seconds (24 hours). The default is zero seconds. Time delays are not used by the standard relay. Relay Types Standard: This is the default relay type. Its transition is completed based upon the sample interval. Delay Before Make: This relay type delays the output of the DI = 1 state/value following a transition of the discrete input from 0 to 1. The duration of the delay is defined by the time delay parameter. The time delay only affects the output of the DI = 1 state/value. When the discrete input transitions from 1 back to 0, the relay immediately directs the DI = 0 state/value to the module output. Delay Before Break: This relay type delays the output of the DI = 0 state/value following a transition of the discrete input from 1 to 0. The duration of the delay is defined by the time delay parameter. The time delay only affects the output of the DI = 0 state/value. When the discrete input transitions from 0 to 1, the relay immediately directs the DI = 1 state/value to the module output.


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DIRECT DIGITAL CONTROL Relay Module (RELAY)

Interval Timer: This relay type sustains the output of the DI = 1 state/value for a specified duration following a transition of the discrete input from 0 to 1. The DI = 1 state/value is directed to the module output for a duration defined by the time delay parameter. When the time delay expires, the output automatically reverts back to the state/value of the DI = 0 input, regardless of the discrete input state.


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DIRECT DIGITAL CONTROL DDC APPLICATIONS DDC Modules Knowing the DDC modules is not enough. You will need to experiment and design programmes utilising the different DDC modules and calculations. For it’s only by use that you will become familiar and through experience, competence. Such is the nature of all things in life. The following is an example; The first step is to define a functional specification using all the available information (specification, site inspection, sales data etc.).

Air Handling Unit

Functional Specification: The air-handling unit is started by a time schedule, Monday to Fridays between 08:00 and 18:00 hours. Thirty (30) seconds after the fan has started the heating valve and cooling valve controls are allowed to operate to maintain conditions. The room temperature will be controlled at a set point of 22°C by the DDC controller. The set point is to be accessible to the BMS operator who will be able to alter the set point between 18°C and 26°C. On the event of a set point alteration, a message is to be printed on the event printer, indicating the time; date and who carried out the alteration. On the event that the fan is scheduled to off, both the heating valve and the cooling valve will close.

The next step external point completed, the while you enter

is to design the DDC flow chart and to define the list (addresses). After the point’s list has been system installers can use it to install the equipment and test the programme off site.

Finally the DDC is entered into the DDC controller on site, tested and commissioned.


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DIRECT DIGITAL CONTROL DDC APPLICATIONS Control Diagram

The following is an Air Handling Unit’s control diagram of heating and cooling valves as controlled by a DDC controller.

24

ZONE TEMPERATURE

SETPOINT 22

20 0%

100%

50%

0%

45%

100%

55%

OPEN

100 %

OPEN

HEATING VA LV E

CLOSED 0% 0%


COOLING VA LV E

100%

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SAMPLE PID LOOP CONTROL

CS I Control Systems International

AIR HA ND L ING UN IT H EAT /C OO L CO NT RO L RO UT IN ES

1000 AI ROOM TEMP

1000 AO AHU SE TPO INT

0000 DO AHU STA RT

ON = LOGIC '1'

THIS POINT MAY BE UNDER CONTROL OF A TIME SCHEDULE.

1 AHU ON 30 Secs

30 SECOND DELAY TO ALLOW AIR FLOW TO STABILISE BEFORE ADDING ANY ENE RGY.

NOTE: PROPORTIONAL BAND IS THE TEMPERATURE RANGE FROM FULL HEATING TO FULL COOLING.

110

THE INPUT HIGH LIMIT SHOULD BE SET AT 100 THE OUTPUT HIGH LIMIT SHOULD BE S ET AT 0. IF THE INPUT OF A PID EXCEEDS THE HIGH OR LOW LIMIT THEN THE PID W ILL IMMEDIATELY DEFAULT TO THE CONTROL POINT (50%) THIS FUNCTION SHOULD BE CARRIED OUT BY THE PID MODULE'S LOW LIMIT AND THE P ID MODULE'S HIGH LIMIT IN THE RESIDENT POINT EDITOR.

2 AHU H/C 4%=4Deg 30 0 DIRECT

RAMP

= 10 %

THE PROPORTIONAL BAND OF THE PID IS EXPRESSED AS A PERCENTAGE, NOT AS DEGREES.

CONTROL POINT = 50 %

THEREFORE THE EQUATION TO WORK OUT THE PROPORTIONAL BAND IS AS FOLLOWS: 0 - 100 %

P.B. TEMPERA TURE RANGE (4 degC) (INPUT HIGH LIMIT - INPUT LOW LIMIT) 4 (100 - 0)

3 HEATING 0 - 45% 100 - 0%

3100 AO AHU HE AT V ALV E


= 4%

4 COOLING 55 - 100% 0 - 100%

0 - 100 %

3101 AO AH U CO OL V ALV E

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0 - 100 %

X

100 1

X 1

100



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DIRECT DIGITAL CONTROL DDC Modules This example is a three speed Fan Coil Unit (FCU) with heating and a cooling valve. The FCU is controlled by a MR-632.

Fan Coil Unit

Functional Specification: The fan coil unit is started by a time schedule, Monday to Fridays between 08:00 and 18:00 hours. Ten (10) seconds after the fan has started, the heating valve and cooling valve controls are allowed to operate to maintain conditions. The room temperature will be controlled at a set point of 22°C by the DDC controller. The set point is to be accessible to the BMS operator who will be able to alter the set point between 18°C and 26°C. As the difference between the set point and the controlled variable increases (error increases) the fan is to control from low speed through to medium speed and finally too high speed. On the event of a set point alteration, a message is to be printed on the events printer, indicating the time; date and who carried out the alteration. On the event that the fan is scheduled to off, both the heating valve and the cooling valve will close.

Once again the next step is to design the DDC flow chart and to define the external point list (addresses). After the point’s list has been completed, the system installers can use it to install the equipment while you enter and test the programme off site. Finally the DDC is entered into the DDC controller on site, tested and commissioned.


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Control Diagram

The following is a Fan Coil Unit’s control diagram of a heating valve, cooling valves and fan speed as controlled by a DDC controller.

24

ZONE TEMPERATURE

SETPOINT 22

20 0%

100%

50%

0%

45%

100%

55%

OPEN

100 %

OPEN

CLOSED 0% 0%

HEATING VALVE

COOLING VALVE

60%

100%

60%

FAN SPEED CONTROL

HIGH

HIGH

30%

30%

MEDIUM

MEDIUM

LOW


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DIRECT DIGITAL CONTROL FAN COIL UNIT

CS I C o n t r o l S y s t e m s I n t e r n a t i o n a l

HEAT/COOL CONTROL ROUTINES WITH FAN SPEED CONTROL.

0107 AI I/STAT ROOM TEMP

0108 AO SETPOINT

0105 DO MASTER POINT

18 - 26 degC

ON = LOGIC '1'

THIS POINT RESIDE AS AN INTERNAL POINT W ITHIN THE MR. AN "ATS" TIME SCHEDULE MAY BE ASSIGNED TO IT.

1 FCU ON 10 Secs

CALCULATION MODULE 11 HI VALVE VALUE

110

CALCULATION

2 FCU H/C RAMP LIMIT 6 Deg 45 0 DIRECT

CALCULATION

MODULE 5 LOW REQUEST

= 10%

ON = LOGIC '1'

CONTROL POINT = 50%

CALCULATION

MODULE 7 MED REQUEST

MODULE 9 HIGH REQUEST

ON = LOGIC '1'

ON = LOGIC '1'

0 - 100%

6

0103 AO FCU HEAT VALVE

0 - 100 %


0104 AO FCU COOL VALVE

8 MED FAN 0.5 SEC

LO FAN 0.5 SEC

4 COOLING 55 - 100% 0 - 100%

3 HEATING 0 - 45% 100 - 0%

0 - 100 %

0

0

1

1

0100 DO LOW FAN ON/OFF

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10 HI FAN 0.5 SEC 0 1

0101 DO MED FAN ON/OFF

0102 DO HI FAN ON/OFF



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Micro Regulator Control

R e f e r e n c e : I/NET

System, System Operator Guide “Micro Regulator Control” I/NET System, Technical Reference Guide “Micro Regulator Control”

Micro Regulators (MRs) are small point count controllers that operate on a sub-LAN connected to a Micro Regulator Interface (MRI), Micro Controller Interface (MCI), or 7798 I/SITE LAN. The MRI, MCI, or I/SITE LAN provide the communications gateway to the I/NET controller LAN and support all of the standard DCU functions typical of the model 7716 PCU. The 7792 MRI and the 7793 MCI provide two communication channels (sub-LANs) for MRs. These controllers will occupy a DCU station address for each sub-LAN implemented. The 7798 I/SITE LAN provides only a single communication channel (sub-LAN) and will occupy a single DCU address. Each sub-LAN will support up to 32 MRs of any type. The sub-LANs of the MCI and the I/SITE LAN will also support Door Controllers (7910A DPU, 7920 DPU, 7930 DIU, and 7940 DIO) mixed with MRs. The sub-LANs of all three controllers (MRI, MCI, and I/SITE LAN) also support ASCs mixed with MRs.

Micro Regulator Configuration The MR Configuration editor, for use with the 7792 MRI, and the MCU Configuration editor, for use with both the 7793 MCI and 7798 I/SITE LAN, define which MRs are currently connected to the controller. These editors indicate if the MR is successfully communicating over the sub-LAN Primary channel, Secondary channel (not supported by 7792 MRI) or not at all. These editors present all 32 MRs (single-channel) or 64 MRs (twochannel) for individual selection. If the MR is defined as “Internal,” the controller does not attempt to transmit at that address. If the entry is defined as “MR,” the controller expects the MR to successfully communicate at the selected address.


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Micro Regulator Control Defining MRs as “Internal” and using the off-line database editor provides a convenient way to build databases for the MRs before they are installed. As the MRs are powered up and communications are established, you can change the MR configuration type from “Internal” to “MR” for those addresses that represent actual MR hardware. The system will automatically download all points and modules to the MR when this transition occurs, allowing for system control to begin. When a station restore is performed on a MRI, MCI, or I/SITE LAN, all of the programming information is downloaded to that controller. In addition, the MRI, MCI, or I/SITE LAN further distributes information to MRs you define as external. This allows the MRs to function in a stand-alone mode if sub-LAN communications are severed between the MRI, MCI, or I/SITE LAN and the MRs. Because this transfer of information between the host (MRI, MCI, or I/SITE LAN) and MRs can be rather lengthy, a “Please Stand By Message” appears anytime you perform a station save or station restore to a 7793 MCI, or 7798 I/SITE LAN. N o t e : A MR must be specified as “MR,” a DPU must be specified as “DPU,”

and an ASC must be specified as “ASC.” Failure to do so will result in communication problems to the sub-LAN device. An asterisk (“*”) at the end of the Type column indicates that the MRI, MCI, or I/SITE LAN cannot establish communications with the MR. The asterisk disappears when successful communications are established. For the MCI and I/SITE LAN, closed-loop communication is supported that enables primary and secondary path communications. In the event of communications failures, one of three characters will appear at the end of the Type column:

Note:

•

A “1” indicates normal communications from the channel’s primary port.

•

A “2” indicates communications over the channel’s secondary port due to a primary port communications failure.

•

A red asterisk (“*”) at the end of the Type column, it means that there is a total communications failure with this MR.


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Micro Regulator Control Creating the MRI Database Database entries for each MR are made by connecting to a MRI, MCI, or I/SITE LAN and then selecting the desired point or extension editor from the main edit menu. The MRI, MCI, or I/SITE LAN and MRs can use bit offset (BB) addresses for hardware output points. This makes it possible for all ten input and output points (00-09) to reside at the same point (PP) address and allow an MRI, MCI, or I/SITE LAN with 32 MRs to occupy only one station (SS) address. Remember that a point address is in the form LLSSPPBB (link, station, point, and bit offset). N o t e : Except for the MR160, bit offset addresses that are not used by the

MR may be used by the MRI/MCI as internal or indirect points. The MR160 has no output point capability. Therefore, for this Micro Regulator type, output point addresses may not be used as internal or indirect points by the MRI/MCI. For MRs and DPUs defined as “Internal” in the MCU Configuration editor, bit offset addresses 00-09 can be defined as External, Internal, or Indirect resident points. However, for MRs, DPUs, and ASCs defined as “MR,” “DPU,” “DIO,” “DIU,” or “ASC” in the MCU configuration editor, only Internal and External resident points should be defined. Indirect resident points should not be used. N o t e : The Minimum Trip and Minimum Close parameters are not used for

MR output commands. The editor lets you enter a value in these fields; however, this information is not downloaded to the MR. MR Parameters This option only appears when you are connected to a 7792 MRI, 7793 MCI, or 7798 I/SITE LAN. These options let you define the hardwarespecific parameters for each MR on the sub-LAN. N o t e : These parameters are not available with the MR160. Although this

editor can be accessed when connected to an MR160, attempts to enter data into any of the fields will result in an “MCU mem overflow” error message.


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Micro Regulator Control The parameter's editor defines the points that will be controlled or displayed locally with the I/STAT or M/STAT. Using this parameter editor, the operator can establish the master device control point, the call point, and the inactivity time-out intervals used by the I/STAT or M/STAT, and the I/STAT or M/STAT password.

N o t e : the I/STAT or M/STAT (an intelligent thermostat connected to the

MR) uses the parameters in this edit screen. The I/STAT or M/STAT controls and monitors points and devices connected to the MR. These parameters are stored in the MR’s NOVRAM. They can be cleared parameters cannot be edited in the off-line database editor, nor are they saved in the database save file. If a MR is replaced or NOVRAM is cleared, the parameters must be entered manually.


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Field Master Device Control

Call Address

Inactivity Time-outs

Password Digits

Description The point address or name of the point to be used as the master device control point is entered here. This point is either a DO or DC point. The Interval field allows you to specify the time from 0 to 255 minutes that the interval timer will be turned on when this point is activated through the On/Off button on the I/STAT. This address and point type defines the point that is controlled on or off when you press the I/STAT’s Call button. This point may be a DO or DC point. The I/STAT and M/STAT use two inactivity time-outs to exit from the Service function or return to the Home LED display when in the normal mode. The timer starts counting down from the time the last button is pressed. For both the “Escape from Service” and “Return to Home LED” time-out intervals enter a duration of 0 – 255 seconds. The I/STAT or M/STAT has built in security in the form of a three-digit numeric password. The password restricts access to the Service function on the I/STAT or M/STAT (the ability to make calibration, point, and parameter changes through the I/STAT or M/STAT). Enter the three digit numeric password for the I/STAT or M/STAT in this field.


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Micro Regulator Control LED Functions There are four LEDs on the I/STAT or M/STAT. Any of the four LEDs may be designated as the Home LED. Using the select keys, each of the four point addresses associated with the LEDs may be selected for viewing. The I/STAT or M/STAT will return the display to the selected Home LED after the “Return to Home LED” inactivity time-out expires. LED 1 allows you to enter a master set point address as the Base address and a local set point address as the Adjust address. Both the Base address and the Adjust address must be local to the same MR (they must have the same PP portion defined in their address). This allows you to locally make changes to a common system set point from the I/STAT or M/STAT using the Change +/– keys and display the newly adjusted set point value at the I/STAT or M/STAT. The displayed value is a summation of the Base (common) address value and the Adjust (local) address value. The Adjust (local) address must be an AO point so that changes may be made through the I/STAT or M/STAT. The Base address may be an AI or AO point. Both points may be external or internal points. If the Base address master set point is received from another address external to the MR, you must attach a calculation extension to the base address (i.e. P0 = Master Set point) in the MRI/MCI. Without a Base address defined; only the value of the Adjust address will display through the I/STAT or M/STAT. If the Adjust address is not defined, then no value will display through the I/STAT or M/STAT.

Note:

If the displayed value of the Adjust address and Base address is needed for other applications, you must create a separate calculation module that sums the two point address values and outputs the result of the calculation to another internal AO point or line. Depending upon the point type being displayed, certain parameters can be defined for each LED. •

AI – no parameters allowed. This point type is display only on the I/STAT or M/STAT.

•

AO – there are three parameters that this point type supports: Increment – the value by which the analogue output value is changed each time a Change arrow button is pressed on the I/STAT or M/STAT. Low – the lowest value to which the point may be adjusted. High – the highest value to which the point may be adjusted.


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Micro Regulator Control •

DO/DC/DI/DM/DA – these point types support up to 2 I/STAT state descriptions. Each I/STAT state description may be 3 characters long. Any alphanumeric character that can be displayed on a 7-segment display can be defined in the 3- character I/STAT state description.

N o t e : The following characters do not “map” to the 7-segment display on

the I/STAT or M/STAT, and therefore cannot be used in the I/STAT state descriptions: K, M, Q, R, T, V, W, X, Y, and Z.

Hardware Coefficients

The Span field offers a normal span and narrow span. The normal span allows the full range of the 0–5VDC or 0–10 VDC to be used. The narrow span allows a 2–4VDC range to be used on 0–5VDC inputs, and a 4–8VDC range to be used on 0–10VDC inputs.


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Micro Regulator Control - Use with STR 250 The STR250 replaces the I/STAT LCD with regard to major functionality such as indoor and outdoor temperature indication, set point adjustment, bypass mode and fan speed commands. The STR250 can be used with the 7728, MRs, and Xenta 102-AX controllers.

1. Increase Button The increase button is used to increase the temperature set point. 2. Decrease Button The decrease button is used to decrease the temperature set point. If the room temperature is being displayed when a button is pushed for the first time, the current effective set point will be displayed. A second push will change the value. 3. Select Button The Select button is used to step through the menu – LED Functions 1 through to 4. 4. Bypass Button The bypass button is used to change the Manual Control device point described previously. Controller Dependant The functions of the STR250 are controller dependent. configurations are carried out using an M/STAT module.


All

local

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DIRECT DIGITAL CONTROL Adjusting the Room Temperature Use the Select button to step through the menu until the Increase and Decrease arrows are displayed. In this mode, change the temperature set point using the Increase/Decrease buttons. Configuration of this is identical to with the I/STAT.

Monitoring the Temperature Use the Select button to step through the menu items allocated through the LED Functions 1 to 4. The default STR display settings are as follows: LED LED LED LED

Function Function Function Function

1: 2: 3: 4:

Set Point Fan Control Indoor Temperature Outdoor Temperature

Example shown below:

Adjusting the Fan Speed Use the Select button to step through the menu until the fan symbol is displayed. If the fan is controllable, use the Increase/Decrease buttons. Note: The Call Button is not associated with any of the 4 buttons described above.


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DIRECT DIGITAL CONTROL Micro Regulator Control

These conversion parameters set the FM (factory slope) and FB (factory offset) conversion coefficients in the MR. The m value can vary between 0 and 1.9997, and the b value can vary between -127 and 127. These parameters are primarily used by TAC for factory-made adjustments. N O T E:

T h e e n d - u s e r s h o u l d a v o i d a l t e r i n g t h e s e h a r d w a r e c o e f f i ci e n t settings.

Lookup Tables MR88, MR632, MR160, and MR88R Lookup Tables Micro Regulator Models MR88, MR632, MR160, and MR88R provide four lookup tables to accurately translate the non-linear characteristics of thermistors. These are designated LUT #1 Normal, LUT #1 Narrow, LUT #2 Normal, and LUT #2 Narrow. N o t e : There are several variations of curves, dissipation characteristics,

and accuracy's available for 10K ohm thermistors – not all 10K-ohm thermistors are alike. Thermistor characteristics must correspond to Dale part # IM1002-C3 (Dale curve #1) to be used with the MR family. The MR range has built in lookup tables to cater for the 10K-ohm TAC (Dale) Thermistor. The lookup table selection and the appropriate conversion coefficient must be used to enable accurate sensor readings. The lookup tables translate the thermistor-controlled voltage directly to temperature in degrees centigrade with a 100° positive bias to permit readings below zero.


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Micro Regulator Control The lookup table entries are defined by the equation 100 (°C + 100). The output from the lookup table is used with the user-defined m and b conversion coefficients to create the engineering unit value. The typical M and B coefficients are as follows: I/STAT sensor: on I/STAT port.

degC

m = 0.0100 b = -100 Lookup Table = 1

10K ohm Thermistors:

degC

m = 0.0100 b = -100 Lookup Table = 2

When connecting a 10K-ohm thermistor to the I/STAT input on any MR, you should specify the database point to use Lookup Table 1. Table number 1 accounts for an elevated self-heating error that is a function of the I/STAT communications interface. A separate pair (normal and narrow) of Lookup tables defined as Lookup Table 2, is provided in the MR firmware to support accommodation of thermistors on the other universal inputs of the MR. The factory-defined lookup tables takes into consideration the normal versus narrow span selection and no change to the conversion coefficients is required. There is actually a Normal Table number 1 and 2 and a Narrow Table number 1 and 2.


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Micro Regulator Control MR55X Lookup Tables The MR55X provides two Lookup tables (Table 1 Normal and Table 2 Normal) to accurately translate the non-linear characteristics of thermistors, and one Lookup table (Table 3) to translate the characteristics of the on-board CFM velocity sensor. These lookup tables are not the same as the lookup tables in the other MRs, because of the different temperature span. N o t e : There are several variations of curves, dissipation characteristics,

and accuracy’s available for 10K ohm thermistors – not all 10K thermistors are alike. Thermistor characteristics must correspond to Dale part # IM1002-C3 (Dale curve #1) to be used with the MR family. The lookup tables translate the thermistor-controlled voltage directly to temperature in degrees centigrade with a 100° positive bias to permit readings below zero. The lookup table entries are defined by the equation 100(°C + 100). The output from the Lookup table is used with the user-defined m and b conversion coefficients to create the engineering unit value. The typical m and b coefficients are as follows: For engineering units of °C:

m = 0.0100

b = –100

For engineering units of °F:

m = 0.0180

b = –148

When connecting a 10 K ohm thermistor or I/STAT to the space sensor input on a MR, specify the database point to use Lookup Table 1. Table number 1 accounts for an elevated self-heating error that is a function of the I/STAT communications interface. A separate Lookup table, defined as Table number 2, is provided in the MR55X firmware to support accommodation of thermistors on the other four general-purpose inputs. Table number 3 is used only to translate the characteristics of the on-board CFM velocity sensor. N o t e : Only Normal lookup tables 1 and 2 are available in the MR55.

Narrow lookup tables are not available.


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Micro Regulator Control Stand-alone ATS Normal ATS functions are supported in the MCI, MRI, and I/SITE LAN. Stand-alone ATS is intended to be the fallback solution for ATS scheduling if there is a break in the MR Sub-LAN communications.


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Micro Regulator Control Stand-alone ATS (continued) The Stand-alone ATS is a MR-resident ATS schedule programmed into the MRs. Stand-alone ATS allows a single start and stop time for each day of the week, and controls the point designated as the master device control point in the MR parameters editor.

N o t e : I f M R p o w e r is l o s t a n d s u b s e q u e n t l y r e s t o r e d f o l l o w i n g a n M R I / M C I - t o - M R c o m m u n i c a t i o n s f a i lu r e , t h e m a s t e r d e v i c e c o n t r o l p o i n t ( c o n t r o l l e d b y t h e M R St a n d - a l o n e A T S sc h e d u l e ) w i l l d e f a u l t t o i t s d e e n e r g i s e d st a t e . No further time-based c o m m a n d s w i ll b e i s s u e d t o t h e p o i n t u n t i l M R I / M CI - t o - M R c o m m u n i c a t i o n s a r e r e - e s t a b li sh e d .


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Micro Regulator Control Direct Digital Control Modules N o t e : MR-resident DDC is not available with the MR160.

Although this editor can be accessed when connected to an MR160, attempts to enter a DDC module will result in a repetitive “ MCU mem overflow” error message. The MR controllers support six DDC module types and an interconnected control configuration of up to 16 DDC modules, depending upon the type of modules. The DDC modules supported include: • • • • • •

Two-Position (2-Pos) module, Proportional, Integral, Derivative (PID) module, Floating (FLT) module, Reset module, Relay module, Calculation (Calc) module.

The MR controllers do not support the HiLo module. Assign DDC modules to a MR by connecting to the desired MRI, MCI, or I/SITE LAN and selecting MR DDC from the edit menu.


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N o t e : MR-resident DDC modules only reside in the MR (not in the MCI, MRI,

or I/SITE LAN. Therefore, these DDC modules are not available for use in any MR tagged as Internal in the MCU configuration editor. The lines that interconnect the DDC modules are numbered so that the line number always corresponds to the DDC module number that outputs to the line. To preserve MR memory, the process variable (PV) input to the PID, Float, and 2-Pos modules, the primary and secondary inputs to the Reset module, and the coil input to the Relay module cannot be defined as “Constant.” Instead, these inputs are selectable as “Line” or “Point”. For the same reason, the floating (FLT) module can only be defined as “Point In a 7792 MRI, 7793 MCI, or 7798 I/SITE LAN, DC/DM points should only be controlled by 7792/3/8 resident programs. This includes the calculations, ATS, temperature control, and demand control editors.

Note:

N O TE:

M R - r e si d e n t points.

DDC should

not

be used


to

control

D C/ D M

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Micro Regulator Control Calculation Module This is a DDC module that exists only in the MR controllers. The Calculation module is edited similarly to the existing DCU calculated point in the I/NET program. The module also operates similarly with some exceptions

N o t e : Indirect AO points cannot be used as the input to a Calculation

module for MRIs, MCIs, and resident MRs.

MR-to-MR Copy This function copies the data in one MR to another MR. The data copied using this function consists of resident I/O point data, extensions, and MR-resident DDC modules. The MR-to-MR copy function does not copy any of the MR parameters (hardware coefficients, standalone ATS, or I/STAT parameters).


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Micro Regulator Control Micro Regulator Editors The Micro Regulator, with certain limitations, may be used for nearly all functions and extensions available in other DCUs. You may use a Micro Regulator and an associated MRI, MCI, or I/SITE LAN to perform/define any of the following editors: Resident and Indirect Points Calculated Points Event Definitions Event Sequences Event Actions Runtime Consumption Alarm Inhibit

Time Scheduling Special Days Temperature Control Demand Control MR-Resident DDC Modules Trend Sampling Trend Plot

MCI, MRI, or I/SITE LAN Resident Programming The following editors only reside in the MRI, MCI, or I/SITE LAN:

Configuration/Status Station Save Station Restore Station Parameters Control Descriptions Control Commands State Descriptions Conversion Coefficients Engineering Units Resident I/O Points Calculations Event Definitions

Event Sequences Event Actions Runtime Consumption Alarm Inhibit Time Scheduling Demand Control Temperature Control Special Days MR-DDC History/Tuning MR Configuration

Even though an extension is resident in the MRI, MCI, or I/SITE LAN, it may be used to perform a control function in a MR. Keep in mind the possibility of lost communications due to a severed sub-LAN communications link between the controller and MRs. Only those editors listed below as resident in the MR can continue to work correctly if communications are severed between the controller and MR.


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Micro Regulator Control MR-Resident Programming The following editors reside in both the MR and the MRI, MCI, or I/SITE LAN controller: •

Station parameters Control commands Conversion coefficients

•

Resident I/O points

•

MR-resident DDC modules


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Direct Digital Control

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