direct digital control

8/9/2019 Direct Digital Control

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TAC Pacific Technical

Training

Course: 2003AP TAC I/NET SevenBMS Programming

Reference ManualSection 3 Direct Digital Control


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DIRECT DIGITAL CONTROL

TAC BMS REFERENCE MANUALRevision 1.0.0 Page 3 - 1


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CONTENTS Page

DIRECT DIGITAL CONTROL 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

DDC APPLICATIONSAir Handling Unit 3 - 31

Fan Coil Unit 3 - 36

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 Control

Re f e r e n c e : I/NET SEVEN, System Operator Guide, Direct DigitalControl.

I/NET SEVEN, Technical Reference Guide DirectDigital Control.

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

DDC is many things. It may be something as simple as measuring aninput temperature, comparing the temperature against the defined setpoint, determining the difference between the input and the set pointtemperatures, and determining if that difference is positive ornegative. The system then issues the appropriate command to bringthe input temperature in line with the set point.

DDC also operates at a more complex level. It can take intoconsideration such factors as the magnitude of an error change sincethe last time the point was sampled. It can also determine the speedat which the error is increasing or decreasing and make corrections asappropriate. This is an example of proportional, integral, andderivative (PID) control. PID is just one of the module types availablewith I/NET.

There is an unfortunate tendency to interchange the terms DDC andPID. 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 DDCemulates pneumatic control devices using an on-line module editor.You dont need to be a technical wizard to use DDC and you dont

need any special training or retraining before you add or modify yourDDC control strategy.


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Input and Output Designations

DDC module inputs are referred to as set points or process variables.

Outputs are referred to as control outputs. I/NET requires that allDDC inputs be defined as points, lines, or constants. Outputs can bedefined as either lines or points.

Points

Points can be used as inputs to DDC modules when the input is theresult of a calculation (internal point), the state/value sensed by anexternal 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 inputsand outputs as points by entering either the point name or the pointaddress.

Lines

It is often desirable, or necessary, to chain several DDC modulestogether in a cascade of control. This requires some way of makingthe output of one module available to other modules. This is

accomplished with lines. These lines can transmit analogue ordiscrete data. Lines are equivalent to pneumatic tubinginterconnecting pneumatic control devices and generally follow thesame rules:

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

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

N o t e : The HiLo and Floating module types have two outputs. When youassign a line number to the first output of one of these modules, werecommend that you leave the next available DDC module numberblank thus allowing you to use it's number if and when you add thesecond output to avoid future confusion.


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Constants

Constants are values or state conditions that never change. Theyremain 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. Aconstant output from a DDC module would make the moduleunnecessary.

AHU H/C

8%=4Deg

300

0

DIRECT

2AHU ON

10 Secs

1

HEATING

0 - 45%

100 - 0%

3

COOLING

55 - 100%

0 - 100%

4

AHU HEAT VALVE

3100 AO

AHU COOL VALVE

3101 AO

AHU ENABLE

0001 DI

AHU SETPOINT

1000 AO

RETURN AIR TEMP

0000 AI

CALCULATION

ON = LOGIC '1'

THIS POINT REFLECTS

THE TIME SCHEDULE

POINT.

0 - 100 % 0 - 100 %

110

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 modulehas its own algorithm. With a basic understanding of control theoryand application, these algorithms are easy to understand and apply.

Technically, there are seven types of DDC modules; however, no one-controller type provides all seven module types. The seven DDCmodule types are:

Two-position HiLo (not available in MRs)PID RelayFloating Calculation (MRs only)Reset

The DCUs and PCUs provide all but the Calculation module. MicroRegulator (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 defineparameters such as inputs, algorithm modifiers, and outputdestinations.

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 modulecompares input and set point values and provides an ON/OFF outputsignal to a DO/DC point or line. This type of control is commonly usedfor simple heating or cooling systems, starting and stopping motors,controlling water sprays for humidification, etc. The parameters forthe Two-position module are listed below.

Module NameA name used to describe the module. This name can be up toeight alphanumeric characters.

Sample Interval (sec)A number between 1 and 255 that represents the number ofseconds between module outputs.

Set pointThe desired value of the input point being controlled. Typicallythis is the desired room temperature or something similar. Aline, point, or constant may represent it.


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Set point OffsetYou may want to utilise set point offset if you have defined yourset point as a line or point. Set point offsets are useful whenyou want cascaded control. That is, you have several modules

that share a common set point (line or point) which need to bestaggered in their operating range.

Input (process variable)The input for the module. The point, line, or constant thatrepresents the value of the process being controlled (airtemperature, water pressure, etc.).

Input FilterThis option lets you average up to five previous input values withthe current input value to reduce the impact of rapidly changinginputs. All DCUs/PCUs and MRs use a Yes or No setting, rather

than a value, for the input filter parameter. These devicesautomatically average the last five inputs with the current inputif their input filter parameter is set to Yes.

Input Low LimitThis parameter defines the lower limit of the set point (not theprocess variable input). The module declares the set point nolonger valid if the set point value drops below the input low limit.If the set point drops below the input low limit, the moduleimmediately declares a bad input and, depending on theapplicable 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 LimitThis parameter defines the upper limit of the set point (not theprocess variable input). The module declares the set point nolonger valid if the set point value rises above the input high limit.If the set point value exceeds the input high limit, the moduleimmediately declares a bad input and, depending on theapplicable module, the following action occurs:

The Two-position module outputs the fail-safe CommandState (Off or On, see Fail-safe Command below).

OutputYou 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 eventsequence, to provide intermediate control, or to directly controlan action.


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Fail-safe CommandThe action executed when the input or set point is no longervalid. Use this option to plan system response to a set point orsensor failure. Acceptable settings are Offor On.

N o t e : 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 l l 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 ct 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 l l 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 ct i v a t e d .

The fail-safe command is executed if the set point exceeds theinput high or input low limits or if the process variable inputexceeds its sensor limits as defined in the resident I/O pointseditor.

DifferentialThe degree of precision for this module. Differential is the rangeof process variable that causes the output to switch from 'On' to'Off'.

ModeThe mode you select determines what happens when the input ishigher 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 risesabove the set point plus one half the differential. Themodule issues a logic '1' command to the output point or

line if the input falls below the set point minus one half thedifferential.

Reverse: The two position module issues a logic '1'command to the output point or line if the input risesabove the set point plus one half the differential. Themodule issues a logic '0' command to the output point orline if the input falls below the set point minus one half thedifferential.


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Proportional, Integral, Derivative Module (PID)

The terms proportional, integral and derivative describe the outputresponse of a module based on a varying set of conditions occurringby the process variable. Each of the three elements of PID has a

distinctive purpose:

Proportional: This element can best be described as coarsecontrol, which provides a rapid response to an error (i.e.,the difference between the set point and the processvariable). All proportional control has an inherent flawcalled offset, which simply means that it will alwayscontrol at a point above or below set point.

Integral: The integral element of PID can best as fine tuningproportional control. It produces an effect that is designedto reduce the offset (inherent to proportional control) tozero.

Derivative: A lead adjustment which produces an outputpreceding the proportional output based on the rate ofchange in the error signal. Derivative control reducesupsets due to sudden load changes, which rarely occur inair conditioning control.

The PID module is commonly used for the control valves, vanes ormodulating motors where an analogue is used. This module comparesthe current input and set point to determine the current error.Proportional, Integral, and Derivative corrections to an analogueoutput point can then be made depending on the magnitude anddirection of this error. The parameters for the PID module are listedbelow.


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Module Name

A name used to describe the module. This name can be up toeight alphanumeric characters.



Set point OffsetYou may want to utilise set point offset if you have defined yourset point as a line or point. Set point offsets are useful whenyou want cascaded control. That is, you have several modulesthat share a common set point (line or point) which need to bestaggered in their operating range.


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Input FilterThis option lets you average up to five previous input values withthe current input value to reduce the impact of rapidly changinginputs. All DCUs/PCUs and MRs use a Yes or No setting, ratherthan a value, for the input filter parameter. These devicesautomatically average the last five inputs with the current inputif their input filter parameter is set to Yes.

Input Low LimitThis parameter has two (2) functions. In the first function thisparameter defines the lower limit of the modules set point (not

the process variable input). The module declares the set pointno longer valid if the set point value drops below the input lowlimit. If the set point drops below the input low limit, themodule immediately declares a bad input and, depending onthe applicable module, the following action occurs:

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

The Input Low Limits second function defines the PIDs Input

Low Limit when calculating Proportional Band (PB). SeeProportional Band page 3 - 13.

Input High LimitThis parameter has two (2) functions. In the first function thisparameter defines the upper limit of the modules set point (notthe process variable input). The module declares the set pointno longer valid if the set point value rises above the input highlimit. If the set point value exceeds the input high limit, themodule immediately declares a bad input and, depending onthe applicable module, one of the following actions occur:

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


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The Input High Limits second function defines the PIDs InputHigh Limit when calculating Proportional Band (PB). See

Proportional Band page 3 - 13.

OutputYou 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 eventsequence, to provide intermediate control, or to directly controlan action.

Output Ramp Limit (percent)The output ramp limit is a value (percent) between 0 and 100used to define the magnitude of the largest change in output youwant the system to issue between samples.

Output Low LimitThe output low limit defines the minimum output value. Thedefault is zero because the output of the module is typically inpercent. For example, you could use this parameter to limittravel in a valve or damper actuator.

Output High LimitThe output high limit defines the maximum output value. Thedefault is 100 because the module output is typically in percent.For example, you could use this parameter to limit travel in avalve or damper actuator.

Control Point (Fail-safe)This is a number between 0 and 100 percent. The default is 50percent. This parameter value is output from the PID moduleunder the following conditions:

The process variable is the same as the set point, P-onlyMode of Operation.

The set point exceeds the modules input high or low limitparameters.

The input point (input to the module) exceeds its sensorhigh or low limit you specified when you defined the AIpoint in the Resident I/O editor.

Proportional Band (percent)In DCUs and PCUs, this is the percent of the input range (therange between the modules Input High Limit and Input LowLimit) that the input value must change in order to change theoutput from zero to 100 percent.


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In DCUs and PCUs, proportional band is defined by the followingequation:

Proportional Band in engineering units (C) x 100Range between the high and low sensor limits 1

Reset Interval (seconds)Use this function to eliminate a persistent error that is not ofsufficient magnitude (as measured at the specified sampleinterval) to create a change in the output. This error called

offset.

Actuator ModeThis parameter defines the response of the PID module.

Direct: If you select this mode, the PID module increasesits output if the input rises. The PID module decreases itsoutput value if the input falls.

Reverse: If you select this mode, the PID moduledecreases its output if the input rises. The PID moduleincreases 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. Thedefault is zero seconds. Use this function to compensate forlarge input changes by comparing the direction and magnitude ofthe error between samples and correcting the outputaccordingly.

Adaptive ControlThis tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs.This parameter defines the point address or name of the discretepoint that will be used to enable/disable adaptive control.Adaptive control is enabled/disabled by the state of the specifieddiscrete point (disabled = 0 and enabled = 1).

Maximum Bump (percent)This tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs.A number between 0 and 100 percent. The default is 5 percent.This parameter determines the size of the PID or Floating outputstep change for automatic tuning in reference to the modulecontrol point (PID) or mid-scale position (Float). The bumpshould be large enough to cause a change in the input (processvariable) that is greater than the noise band, but not so large asto damage the controlled equipment. The typical range is 5 to 25percent.


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Settling Time (seconds)This tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs.

The settling time can be between 10 and 1,800 seconds. Thedefault is 120 seconds. This parameter is an estimate of thetime it takes for the input (process variable) to settle down aftera set point change. It is used for automatic and adaptive tuningas the minimum time interval between a process disturbanceand the next action. For automatic tuning, it is the time intervalbetween setting the output to either the control point (PID) or tomid-scale (Floating) and the beginning of the tuning cycle. Foradaptive tuning, it is the minimum time that will be observedbetween parameter calculations.

You can best estimate the settling time by observing the input

settling time after a natural process disturbance. To do this, youmeasure the time interval from the point of the disturbance to apoint where the effects of the disturbance are negligible. Thetypical range is between 30 and 150 seconds.

Maximum Overshoot (percent)This tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs.This parameter is a number between 0 and 100 percent. Thedefault is 10 percent. This parameter, along with target

damping (described below), controls the shape of the initialoutput response to a process disturbance. The magnitude of themodule response is a qualitative measure of the controller. Thetypical range for this parameter is between 10 and 50 percent.

Target Damping (percent)This tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs.Target damping can be set to a value between 1 and 75 percent.This parameter represents the desired reduction in the processvariable overshoot from the first overshoot (maximumovershoot) to the second, and so on. A value of 25 percentmeans the second over-shoot magnitude should be 25 percent ofthe first. The recommended value for this parameter is thedefault: 25.


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Noise Band (percent)This tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs.

Noise band can be set to a value between 0 and 100 percent.The default is 2 percent. This parameter, specified as apercentage of the input range, is the minimum process variablechange that initiates an adaptive calculation of the moduleparameters (provided the Adaptive Control discrete pointdescribed above is equal to one). Because adaptive tuningattempts to reshape the process variable response after everysuch change, it is important to make the noise band big enoughto prevent inadvertent unnecessary tuning. The typical range isbetween 2 and 10 percent.


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Floating Module (FLOAT)

The Floating module operates much like the PID module, describedabove. 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 modulealways knows where the output is). The output of the PID module isalways a percentage of the full-scale output. The output of theFloating module is directed to two separate DO points as an increasecommand and a decrease command. The module does not know theexact position of the controlled valve or damper and assumes that thecontrolled device was driven to the correct position. You need thismodule and its outputs when a bi-directional motor controls the finalcontrol element (valve, damper, etc.). The parameters for theFloating module are listed below.


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Set point OffsetYou may want to utilise set point offset if you have defined yourset point as a line or point. Set point offsets are useful when

you want cascaded control. That is, you have several modulesthat share a common set point (line or point) which need to bestaggered in their operating range.


Input FilterThis option lets you average up to five previous input values withthe current input value to reduce the impact of rapidly changinginputs. All DCUs/PCUs and MRs use a Yes or No setting, rather

than a value, for the input filter parameter. These devicesautomatically average the last five inputs with the current inputif their input filter parameter is set to Yes.

Input Low LimitThis parameter has two (2) functions. In the first function thisparameter defines the lower limit of the modules set point (notthe process variable input). The module declares the set pointno longer valid if the set point value drops below the input lowlimit. If the set point drops below the input low limit, themodule immediately declares a bad input and, depending onthe applicable module, the following action occurs:

The Floating module stops any pulse outputs.

The Input Low Limits second function defines the PIDs InputLow Limit when calculating Proportional Band (PB). See



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Input High LimitThis parameter has two (2) functions. In the first function thisparameter defines the upper limit of the modules set point (notthe process variable input). The module declares the set point

no longer valid if the set point value rises above the input highlimit. If the set point value exceeds the input high limit, themodule immediately declares a bad input and, depending onthe applicable module, one of the following actions occur:

The Floating module stops any pulse outputs.

The Input High Limits second function defines the PIDs InputHigh Limit when calculating Proportional Band (PB). See


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 beused as the output. In the UC, the user simply enters thehardware bit (0 7) to be controlled by the UC Floatingextension.The Floating module issues timed pulse outputs to rotate a bi-directional motor. This parameter directs a timed pulse toincrease the output. This results in a specific action, such as theopening of a valve.

Output (Decrease)In a DCU or PCU, you may use a line or a DO point for thisparameter. 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 thehardware bit (0 7) to be controlled by the UC Floatingextension.This parameter reverses the activity instigated by the outputincrease, described above. For example, if the increase pulseopens a valve, the decrease pulse closes a valve.

Throttling Range (seconds)This parameter defines the number of seconds it takes for theactuator to move from being fully open to fully closed and viceversa. This time becomes the maximum increase/decrease pulseduration time. For the Floating module, enter a number between0 and 255. The default is zero.


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Turn-Around (seconds)This parameter defines the number of seconds it takes tocomplete 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. Thedefault is zero.Note: Most actuator manufacturers do not give this parameterwithin the actuators technical data. A setting of 0 secondscould be used.

Proportional Band (percent)In DCUs and PCUs, this is the percent of the input range (therange between the modules Input High Limit and Input LowLimit) that the input value must change in order to change theoutput 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 ofsufficient magnitude (as measured at the specified sampleinterval) to create a change in the output. This error called

offset. This is the rate portion of the PID or Floating modulealgorithm. Enter a number between 0 and 3,600 for the rateinterval. The default is zero seconds. Use this function tocompensate for large input changes by comparing the direction

and magnitude of the error between samples and correcting theoutput accordingly.

Actuator ModeThis parameter defines the response of the PID or Floatingmodule.

Direct: If you select this mode, Floating module issues anincrease pulse if the input rises. The Floating moduleissues a decrease pulse if the input falls.

Reverse: If you select this mode, the Floating moduleissues a decrease pulse if the input rises. The Floatingmodule issues an increase pulse if the input falls.

Adaptive ControlThis tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs.This parameter defines the point address or name of the discretepoint that will be used to enable/disable adaptive control.Adaptive control is enabled/disabled by the state of the specifieddiscrete point (disabled = 0 and enabled = 1).


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Maximum Bump (percent)This tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs.

A number between 0 and 100 percent. The default is 5 percent.This parameter determines the size of the PID or Floating outputstep change for automatic tuning in reference to the modulecontrol point (PID) or mid-scale position (Float). The bumpshould be large enough to cause a change in the input (processvariable) that is greater than the noise band, but not so large asto damage the controlled equipment. The typical range is 5 to 25percent.

Settling Time (seconds)This tuning parameter is available in the PID and Floatingmodules 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 thetime it takes for the input (process variable) to settle down aftera set point change. It is used for automatic and adaptive tuningas the minimum time interval between a process disturbanceand the next action. For automatic tuning, it is the time intervalbetween setting the output to either the control point (PID) or tomid-scale (Floating) and the beginning of the tuning cycle. Foradaptive tuning, it is the minimum time that will be observedbetween parameter calculations.You can best estimate the settling time by observing the inputsettling time after a natural process disturbance. To do this, you

measure the time interval from the point of the disturbance to apoint where the effects of the disturbance are negligible. Thetypical range is between 30 and 150 seconds.

Maximum Overshoot (percent)This tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs.This parameter is a number between 0 and 100 percent. Thedefault is 10 percent. This parameter, along with targetdamping (described below), controls the shape of the initialoutput response to a process disturbance. The magnitude of themodule response is a qualitative measure of the controller. Thetypical range for this parameter is

Target Damping (percent)This tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs between 10 and 50 percent. Target damping can be set toa value between 1 and 75 percent.


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This parameter represents the desired reduction in the processvariable overshoot from the first overshoot (maximumovershoot) to the second, and so on. A value of 25 percentmeans the second over-shoot magnitude should be 25 percent of

the first. The recommended value for this parameter is thedefault: 25.

Noise Band (percent)This tuning parameter is available in the PID and Floatingmodules of DCUs and PCUs; it is not available in MRs, UCs, andASCs.Noise band can be set to a value between 0 and 100 percent.The default is 2 percent. This parameter, specified as apercentage of the input range, is the minimum process variablechange that initiates an adaptive calculation of the moduleparameters (provided the Adaptive Control discrete point

described above is equal to one). Because adaptive tuningattempts to reshape the process variable response after everysuch change, it is important to make the noise band big enoughto prevent inadvertent unnecessary tuning. The typical range isbetween 2 and 10 percent.


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Reset Module (RESET)

The reset module produces a primary reset schedule and modifies theresults of that schedule based upon a secondary input. The output ofthis module typically provides a set point to another module andgenerally does not directly control an output point. The Reset module

is typically used to reset the set point of a controlling module (Two-position, PID, Floating) based on one or two measured inputs. Thisincreases the rate of space temperature modification but does notimprove control capability.

This reset function is probably familiar to control engineers as thetechnique used to reset the set point of a boiler according to outsideair temperature. As the outside temperature drops, the temperatureof the water must increase to maintain the desired temperature in thespaces served by the boiler (the heating load increases). The twotemperatures are inversely proportional to each other. This functionhas been used for decades in pneumatic control systems and is a valid

concept.

Reset control is also used to reset the discharge temperature of anHVAC unit based on the space temperature.

The parameters for the Reset module are listed below



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Primary InputSelect a line, point, or constant for this parameter. It can alsobe a line that is output from another module, or a constant. In aMR or ASC resident module, only a line or point can be specifieda constant cannot be used.

Primary Inputs 1 and 2These input values, in engineering units of the primary sensedvariable, are the major factor in determining the primary output.These entries are the minimum and maximum values over whichwe wish to reset the primary output.

Primary Outputs 1 and 2These two values define the module output in conjunction withthe primary inputs. These entries determine the minimum andmaximum outputs at the primary input values.

N o t e : At primary input 1, the module outputs the value entered asprimary output 1; the same occurs with primary input 2 andprimary output 2. This lets you define either a directlyproportional reset schedule or an inversely proportional resetschedule.

Secondary Input

Select a line, point, or constant for this parameter. This inputsecondarily resets the output from the module. In a MR- orASC-resident module, only a line or point can be specified aconstant cannot be used.

Secondary Inputs 1 and 2These input values, in engineering units of the secondarymeasured variable, provide a second modifier for the moduleoutput.

Secondary Outputs 1 and 2These output values, in engineering units of the controlledvariable, offset the set point derived by the primary input/outputschedule. In short the resultant of the secondary function isadded to the resultant of the primary function and then sent tothe output.

NO TE: W h e n u s i n g b o t h t h e p r i m a r y i n p u t a n d t h e s e co n d a r y

i n p u t , t h e r e s u l t a n t o f t h e p r i m a r y a n d s e co n d a r y

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 .


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OutputYou 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 controlan action.

Output Low LimitThe output low limit defines the minimum output value. Thedefault is zero because the output of the module is typically inpercent. For example, you could use this parameter to limittravel in a valve or damper actuator.

Output High LimitThe 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 avalve or damper actuator.


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HiLo Module (HiLo)

The HiLo module provides a convenient means to extract the highestand/or lowest discrete state or value from among several discretestates or values. You can also accomplish this with the High and LowOperator calculations in the DCU/PCU. This module is not available in

MRs or ASCs; instead the Calculation module can be used.

N o t e : The HiLo module will deselect any point that is in old data andhappily process the remaining valid inputs. The High or Low functionswithin the calculation editor will not deselect any point that is in olddata.

The HiLo module is commonly used to derive the highest spacetemperature needed to reset an air handling unit (AHU) cold deckdischarge set point, and to select the lowest space temperatureneeded to reset an AHU hot deck discharge set point.

The module is capable of providing both the high signal output and thelow signal output simultaneously, if desired, making it unnecessary touse an additional module.

The parameters for the HiLo module are listed below.



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HiLo Module (HiLo)


Input #1 - 4A line, point, or constant. Each of the four inputs is normally thesame type (analogue or discrete). Mixing of discrete states andanalogue values is typically not done.

Low Signal OutThis parameter directs the minimum output value or logic levelto either a line or a point. The HiLo module is capable ofproviding the high signal output and low signal outputsimultaneously.

High Signal Out

This parameter directs the maximum output value or logic levelto either a line or a point. The HiLo module is capable ofproviding the high signal output and low signal outputsimultaneously.


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Relay Module (RELAY)

The Relay module performs multiple functions as part of overall I/NETDDC capabilities. As you become more familiar with I/NET you willdiscover many uses for the Relay module.

In its simplest form, this module is similar to a single-pole double-throw relay. It has an input which acts as a coil (DI Select), anormally closed port (DI = 0 input), a normally open port (DI = 1input), and a common Output.

When used as a traditional relay, the module passes the state/valuefrom 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 thestate/value of the DI = 1 port to the output.

This module can also function as an interval time delay relay (INT), asa 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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DI SelectThis input can be a line or a point. If you select a point youmust use a DO, DI, DC, or DA point type. If you select a line itmust carry a discrete state (0 or 1) rather than an analoguevalue. This parameter is comparable to a relay coil. If the stateof the line or point entered here is a 1, the relay module is

energised and the module passes the state/value entering atthe DI = 1 port. When the Relay module is deenergised, theDI = 0 state/value is passed to the module output.

DI = 0 InputThis is the state/value passed to the output by the Relay module

when the discrete input (see above) is 0. Select a line, point, ora constant.

DI = 1 InputThis is the state/value passed to the output by the Relay modulewhen the discrete input (see above) is 1. Select a line, point, ora constant.

Time Delay (seconds)This parameter defines the number of seconds for the intervaltimer, delay-before-break, and delay-before-make relays. Entera number between 0 and 86,400 seconds (24 hours). The

default is zero seconds. Time delays are not used by thestandard relay.

Relay TypesStandard: 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 theDI = 1 state/value following a transition of the discreteinput from 0 to 1. The duration of the delay is defined bythe time delay parameter. The time delay only affects theoutput of the DI = 1 state/value. When the discrete inputtransitions from 1 back to 0, the relay immediately directsthe DI = 0 state/value to the module output.

Delay Before Break: This relay type delays the output of theDI = 0 state/value following a transition of the discreteinput from 1 to 0. The duration of the delay is defined bythe time delay parameter. The time delay only affects theoutput of the DI = 0 state/value. When the discrete inputtransitions from 0 to 1, the relay immediately directs theDI = 1 state/value to the module output.


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Interval Timer: This relay type sustains the output of the DI =1 state/value for a specified duration following a transitionof the discrete input from 0 to 1. The DI = 1 state/value is

directed to the module output for a duration defined by thetime delay parameter. When the time delay expires, theoutput automatically reverts back to the state/value of theDI = 0 input, regardless of the discrete input state.


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DDC APPLICATIONS

DDC Modules

Knowing the DDC modules is not enough. You will need to experimentand design programmes utilising the different DDC modules and

calculations. For its only by use that you will become familiar andthrough experience, competence. Such is the nature of all things inlife.

The following is an example;

The first step is to define a functional specification using all theavailable information (specification, site inspection, sales data etc.).

Air Handling Unit

Functional Specification:

The air-handling unit is started by a time schedule, Monday toFridays between 08:00 and 18:00 hours.

Thirty (30) seconds after the fan has started the heating valveand cooling valve controls are allowed to operate to maintainconditions.

The room temperature will be controlled at a set point of 22C bythe DDC controller. The set point is to be accessible to the BMS

operator who will be able to alter the set point between 18C and26C. On the event of a set point alteration, a message is to be

printed on the event printer, indicating the time; date and whocarried out the alteration.

On the event that the fan is scheduled to off, both the heatingvalve and the cooling valve will close.

The next step is to design the DDC flow chart and to define theexternal point list (addresses). After the points list has beencompleted, the system installers can use it to install the equipmentwhile you enter and test the programme off site.

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


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DDC APPLICATIONS

Control Diagram

The following is an Air Handling Units control diagram of heating and

cooling valves as controlled by a DDC controller.

CLOSED

OPEN

24

20

22

ZONE

TEMPERATURE

SETPOINT

0% 100%50%

OPEN

45% 55%0% 100%

100 % HEATING VA LVE 0% 0% COOLING VA LVE 100%


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CSAMPLE PID LOOP CONTROL AIR HA ND LING UN IT H EAT/COOL CONTRO L RO UTINES

AHU H/C

4%=4Deg

30

0

DIRECT

2

AHU ON

30 Secs

1

HEATING

0 - 45%

100 - 0%

3

COOLING

55 - 100%

0 - 100%

4

AHU HEAT V ALV E

3100 AO

AH U COOL VALVE

3101 AO

AHU STA RT0000 DO

AHU SE TPO INT1000 AO

ROOM TEMP1000 AI

110

ON = LOGIC '1'

THIS POINT MAY BE UNDER

CONTROL OF A TIME SCHEDULE.

0 - 100 % 0 - 100 %

RAMP = 10 %

CONTROL

POINT = 50 %

30 SECOND DELAY TO ALLOW AIR

FLOW TO STABILISE BEFORE ADDING

ANY ENE RGY.

0 - 100 %


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DDC Modules

This example is a three speed Fan Coil Unit (FCU) with heating and acooling 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 Fridaysbetween 08:00 and 18:00 hours.

Ten (10) seconds after the fan has started, the heating valveand cooling valve controls are allowed to operate to maintainconditions.

The room temperature will be controlled at a set point of 22C bythe DDC controller. The set point is to be accessible to the BMS

operator who will be able to alter the set point between 18C and26C. As the difference between the set point and the controlled

variable increases (error increases) the fan is to control from lowspeed through to medium speed and finally too high speed.

On the event of a set point alteration, a message is to be printedon the events printer, indicating the time; date and who carriedout the alteration.

On the event that the fan is scheduled to off, both the heatingvalve and the cooling valve will close.

Once again the next step is to design the DDC flow chart and to definethe external point list (addresses). After the points list has beencompleted, the system installers can use it to install the equipmentwhile you enter and test the programme off site.

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


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Control Diagram

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

CLOSED

OPEN

24

20

22

ZONE

TEMPERATURE

SETPOINT

0% 100%50%

OPEN

45% 55%0% 100%

100 % HEATING VALVE 0% 0% COOLING VALVE 100%

HIGH

MEDIUM

LOW

FAN SPEED CONTROL

60%

30%

MEDIUM

30%

HIGH

60%


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FAN COIL UNIT HEAT/COOL CONTROL ROUTINESWITH FAN SPEED CONTROL.

FCU H/C

6 Deg

45

0

DIRECT

2

FCU ON

10 Secs

1

HEATING

0 - 45%

100 - 0%

3 COOLING

55 - 100%

0 - 100%

4

FCU HEAT VALVE

0103 AO

FCU COOL VALVE

0104 AO

I/STAT ROOM TEMP

0107 AI

ON = LOGIC '1'

MASTER POINT

0105 DO THIS POINT RESIDE AS AN

INTERNAL POINT W ITHIN

THE MR. AN "ATS" TIMESCHEDULE MAY BE ASSIGNED

TO IT.

0 - 100 % 0 - 100 %

LO FAN

0.5 SEC

6

M

0

LOW FAN ON/OFF

0100 DO

MED FA

010

MED R

MOD

LOW REQUEST

MODULE 5

HI VALVE

MODU

CALCUL

CALCULATION CALCUL

1 1

0 0

SETPOINT

0108 AO

0 - 100%

110

18 - 26 degC

ON = LOGIC '1'

RAMP LIMIT = 10%

CONTROL POINT = 50%


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Micro Regulator Control

Re f e r e n c e : I/NET System, System Operator Guide MicroRegulator Control

I/NET System, Technical Reference Guide MicroRegulator Control

Micro Regulators (MRs) are small point count controllers that operateon a sub-LAN connected to a Micro Regulator Interface (MRI), MicroController Interface (MCI), or 7798 I/SITE LAN.

The MRI, MCI, or I/SITE LAN provide the communications gateway tothe I/NET controller LAN and support all of the standard DCU functionstypical of the model 7716 PCU. The 7792 MRI and the 7793 MCIprovide two communication channels (sub-LANs) for MRs. These

controllers will occupy a DCU station address for each sub-LANimplemented. The 7798 I/SITE LAN provides only a singlecommunication channel (sub-LAN) and will occupy a single DCUaddress. Each sub-LAN will support up to 32 MRs of any type. Thesub-LANs of the MCI and the I/SITE LAN will also support DoorControllers (7910A DPU, 7920 DPU, 7930 DIU, and 7940 DIO) mixedwith MRs. The sub-LANs of all three controllers (MRI, MCI, and I/SITELAN) also support ASCs mixed with MRs.

Micro Regulator Configuration

The MR Configuration editor, for use with the 7792 MRI, and the MCUConfiguration editor, for use with both the 7793 MCI and 7798 I/SITELAN, define which MRs are currently connected to the controller.These editors indicate if the MR is successfully communicating overthe sub-LAN Primary channel, Secondary channel (not supported by7792 MRI) or not at all.

These editors present all 32 MRs (single-channel) or 64 MRs (two-channel) for individual selection. If the MR is defined as Internal,the controller does not attempt to transmit at that address. If theentry is defined as MR, the controller expects the MR to successfullycommunicate at the selected address.


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Defining MRs as Internal and using the off-line database editorprovides a convenient way to build databases for the MRs before theyare installed.

As the MRs are powered up and communications are established, youcan change the MR configuration type from Internal to MR forthose addresses that represent actual MR hardware. The system willautomatically download all points and modules to the MR when thistransition occurs, allowing for system control to begin.

When a station restore is performed on a MRI, MCI, or I/SITE LAN, allof the programming information is downloaded to that controller. Inaddition, the MRI, MCI, or I/SITE LAN further distributes informationto MRs you define as external. This allows the MRs to function in astand-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, orI/SITE LAN) and MRs can be rather lengthy, a Please Stand ByMessage appears anytime you perform a station save or stationrestore 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 incommunication 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 areestablished.

N o t e : For the MCI and I/SITE LAN, closed-loop communication issupported that enables primary and secondary path communications.In the event of communications failures, one of three characters willappear at the end of the Type column:

A 1 indicates normal communications from the channelsprimary port.

A 2 indicates communications over the channels secondary

port due to a primary port communications failure.

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


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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 editorfrom 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 allten 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 occupyonly one station (SS) address. Remember that a point address is inthe form LLSSPPBB (link, station, point, and bit offset).

N o t e : Except for the MR160, bit offset addresses that are not used by theMR may be used by the MRI/MCI as internal or indirect points. The

MR160 has no output point capability. Therefore, for this MicroRegulator type, output point addresses may not be used as internal orindirect points by the MRI/MCI.

For MRs and DPUs defined as Internal in the MCU Configurationeditor, bit offset addresses 00-09 can be defined as External, Internal,or Indirect resident points. However, for MRs, DPUs, and ASCsdefined as MR, DPU, DIO, DIU, or ASC in the MCUconfiguration editor, only Internal and External resident points shouldbe defined. Indirect resident points should not be used.

N o t e : The Minimum Trip and Minimum Close parameters are not used forMR output commands. The editor lets you enter a value in thesefields; however, this information is not downloaded to the MR.

MR Parameters

This option only appears when you are connected to a 7792 MRI, 7793MCI, or 7798 I/SITE LAN. These options let you define the hardware-specific parameters for each MR on the sub-LAN.

N o t e : These parameters are not available with the MR160. Although thiseditor can be accessed when connected to an MR160, attempts toenter data into any of the fields will result in an MCU memoverflow error message.


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The parameter's editor defines the points that will be controlled ordisplayed locally with the I/STAT or M/STAT. Using this parameter

editor, the operator can establish the master device control point, thecall point, and the inactivity time-out intervals used by the I/STAT orM/STAT, and the I/STAT or M/STAT password.

N o t e : the I/STAT or M/STAT (an intelligent thermostat connected to theMR) uses the parameters in this edit screen. The I/STAT or M/STATcontrols and monitors points and devices connected to the MR.

These parameters are stored in the MRs NOVRAM. They can becleared parameters cannot be edited in the off-line database editor,nor are they saved in the database save file. If a MR is replaced orNOVRAM is cleared, the parameters must be entered manually.


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Field Description

Master Device

Control

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 Intervalfield allows you to specify the time from 0 to 255minutes that the interval timer will be turned onwhen this point is activated through the On/Offbutton on the I/STAT.

Call Address This address and point type defines the point that iscontrolled on or off when you press the I/STATs Callbutton. This point may be a DO or DC point.

InactivityTime-outs

The I/STAT and M/STAT use two inactivity time-outsto exit from the Service function or return to theHome LED display when in the normal mode. The

timer starts counting down from the time the lastbutton is pressed. For both the Escape fromService and Return to Home LED time-outintervals enter a duration of 0 255 seconds.

PasswordDigits

The I/STAT or M/STAT has built in security in theform of a three-digit numeric password. Thepassword restricts access to the Service function onthe I/STAT or M/STAT (the ability to makecalibration, point, and parameter changes throughthe I/STAT or M/STAT). Enter the three digitnumeric password for the I/STAT or M/STAT in thisfield.


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LED Functions

There are four LEDs on the I/STAT or M/STAT. Any of the four LEDsmay be designated as the Home LED. Using the select keys, each ofthe four point addresses associated with the LEDs may be selected forviewing. The I/STAT or M/STAT will return the display to the selectedHome LED after the Return to Home LED inactivity time-out expires.

LED 1 allows you to enter a master set point address as the Baseaddress and a local set point address as the Adjust address. Both theBase address and the Adjust address must be local to the same MR(they must have the same PP portion defined in their address). Thisallows you to locally make changes to a common system set pointfrom 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. Thedisplayed value is a summation of the Base (common) address valueand the Adjust (local) address value.

The Adjust (local) address must be an AO point so that changes maybe made through the I/STAT or M/STAT. The Base address may be anAI or AO point. Both points may be external or internal points.

If the Base address master set point is received from another addressexternal to the MR, you must attach a calculation extension to thebase address (i.e. P0 = Master Set point) in the MRI/MCI.

N o t e : Without a Base address defined; only the value of the Adjustaddress will display through the I/STAT or M/STAT. If the Adjustaddress is not defined, then no value will display through the I/STATor M/STAT.

If the displayed value of the Adjust address and Base address isneeded for other applications, you must create a separate calculationmodule that sums the two point address values and outputs the resultof the calculation to another internal AO point or line.

Depending upon the point type being displayed, certain parameterscan be defined for each LED.

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

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


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DO/DC/DI/DM/DA these point types support up to 2 I/STATstate descriptions. Each I/STAT state description may be 3characters long. Any alphanumeric character that can be displayed

on a 7-segment display can be defined in the 3- character I/STATstate description.

N o t e : The following characters do not map to the 7-segment display onthe I/STAT or M/STAT, and therefore cannot be used in the I/STATstate 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 normalspan allows the full range of the 05VDC or 010 VDC to be used.The narrow span allows a 24VDC range to be used on 05VDCinputs, and a 48VDC range to be used on 010VDC inputs.


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Micro Regulator Control - Use with STR 250

The STR250 replaces the I/STAT LCD with regard to major functionalitysuch 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 ButtonThe increase button is used to increase the temperature set point.

2. Decrease ButtonThe decrease button is used to decrease the temperature set point. If theroom temperature is being displayed when a button is pushed for the firsttime, the current effective set point will be displayed. A second push willchange the value.

3. Select ButtonThe Select button is used to step through the menu LED Functions 1through to 4.

4. Bypass ButtonThe bypass button is used to change the Manual Control device pointdescribed previously.

Controller DependantThe functions of the STR250 are controller dependent. All localconfigurations are carried out using an M/STAT module.


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Adjusting the Room TemperatureUse the Select button to step through the menu until the Increase andDecrease arrows are displayed. In this mode, change the temperature setpoint using the Increase/Decrease buttons. Configuration of this isidentical to with the I/STAT.

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

LED Function 1: Set PointLED Function 2: Fan ControlLED Function 3: Indoor TemperatureLED Function 4: Outdoor Temperature

Example shown below:

Adjusting the Fan SpeedUse 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 buttonsdescribed above.


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These conversion parameters set the FM (factory slope) and FB(factory offset) conversion coefficients in the MR. The m value canvary between 0 and 1.9997, and the bvalue can vary between -127and 127. These parameters are primarily used by TAC forfactory-made adjustments.

NOTE: 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 c i e n t

s e t t i n g s .

Lookup Tables

MR88, MR632, MR160, and MR88R Lookup TablesMicro Regulator Models MR88, MR632, MR160, and MR88R providefour lookup tables to accurately translate the non-linear characteristicsof 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-ohmthermistors are alike. Thermistor characteristics must correspond toDale part # IM1002-C3 (Dale curve #1) to be used with the MRfamily.

The MR range has built in lookup tables to cater for the 10K-ohm TAC(Dale) Thermistor. The lookup table selection and the appropriateconversion coefficient must be used to enable accurate sensorreadings. The lookup tables translate the thermistor-controlledvoltage directly to temperature in degrees centigrade with a 100positive bias to permit readings below zero.


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The lookup table entries are defined by the equation 100 (C + 100).The output from the lookup table is used with the user-defined mandb conversion coefficients to create the engineering unit value. The

typical M and B coefficients are as follows:

I/STAT sensor: degC m= 0.0100 b= -100on I/STAT port. Lookup Table = 1

10K ohm Thermistors: degC m= 0.0100 b= -100Lookup Table = 2

When connecting a 10K-ohm thermistor to the I/STAT input on anyMR, you should specify the database point to use Lookup Table 1.Table number 1 accounts for an elevated self-heating error that is afunction of the I/STAT communications interface.A separate pair (normal and narrow) of Lookup tables defined asLookup Table 2, is provided in the MR firmware to supportaccommodation of thermistors on the other universal inputs of the MR.

The factory-defined lookup tables takes into consideration the normalversus narrow span selection and no change to the conversioncoefficients is required. There is actually a Normal Table number 1 and2 and a Narrow Table number 1 and 2.


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MR55X Lookup Tables

The MR55X provides two Lookup tables (Table 1 Normal and Table 2

Normal) to accurately translate the non-linear characteristics ofthermistors, and one Lookup table (Table 3) to translate thecharacteristics of the on-board CFM velocity sensor. These lookuptables 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 accuracys available for 10K ohm thermistors not all 10Kthermistors are alike. Thermistor characteristics must correspond toDale part # IM1002-C3 (Dale curve #1) to be used with the MRfamily.

The lookup tables translate the thermistor-controlled voltage directlyto temperature in degrees centigrade with a 100 positive bias topermit readings below zero. The lookup table entries are defined bythe equation 100(C + 100).

The output from the Lookup table is used with the user-defined mandb conversion coefficients to create the engineering unit value. Thetypical mand bcoefficients 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 sensorinput on a MR, specify the database point to use Lookup Table 1.Table number 1 accounts for an elevated self-heating error that is afunction of the I/STAT communications interface.

A separate Lookup table, defined as Table number 2, is provided in theMR55X firmware to support accommodation of thermistors on theother four general-purpose inputs. Table number 3 is used only totranslate 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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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 ATSscheduling if there is a break in the MR Sub-LAN communications.


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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 eachday of the week, and controls the point designated as the masterdevice 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 eq u e n t l y r e s t o r e d f o l lo w i n g an

MR I / M CI - t o - M R c om 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 se d st a t e . N o f u r t h e r t i m e - b a s e d

c o mm a n d s w i l l b e is su e d t o t h e p o i n t u n t i l M RI / M CI - t o - M R

c om m u n i c a t i o n s a r e r e - e s t a b l i sh e d .


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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 toenter a DDC module will result in a repetitive MCU mem overflowerror message.

The MR controllers support six DDC module types and an inter-connected control configuration of up to 16 DDC modules, dependingupon 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 DDCmodules to a MR by connecting to the desired MRI, MCI, or I/SITE LANand 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 usein any MR tagged as Internalin the MCU configuration editor.

The lines that interconnect the DDC modules are numbered so thatthe line number alwayscorresponds to the DDC module number thatoutputs to the line. To preserve MR memory, the process variable(PV) input to the PID, Float, and 2-Pos modules, the primary andsecondary inputs to the Reset module, and the coil input to the Relaymodule cannot be defined as Constant. Instead, these inputs areselectable as Line or Point. For the same reason, the floating (FLT)module can only be defined as Point

N o t e : In a 7792 MRI, 7793 MCI, or 7798 I/SITE LAN, DC/DM pointsshould only be controlled by 7792/3/8 resident programs. Thisincludes the calculations, ATS, temperature control, and demandcontrol editors.

NO TE: MR - r e si d e n t D DC s h o u l d n o t b e u s e d t o c o n t r o l D C/ DM

p o i n t s .


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Calculation Module

This is a DDC module that exists only in the MR controllers. The

Calculation module is edited similarly to the existing DCU calculatedpoint in the I/NET program. The module also operates similarly withsome exceptions

N o t e : Indirect AO points cannot be used as the input to a Calculationmodule for MRIs, MCIs, and resident MRs.

MR-to-MR Copy

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


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MR-Resident Programming

The following editors reside in both the MR and the MRI, MCI, or

I/SITE LAN controller:

Station parametersControl commandsConversion coefficients

Resident I/O points

MR-resident DDC modules


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direct digital control

Documents