mcp-096 - addendum to micro iii operation for compressor panels with condenser control

7/27/2019 MCP-096 - Addendum to Micro III Operation for Compressor Panels With Condenser Control

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ADDENDUM TO MICRO III OPERATIONFOR COMPRESSOR PANELS WITH

CONDENSER CONTROL

Document: MCP-96Revision: C

Page 1 of8 Effective: 02-2003

Condenser Control OverviewThe following information supplements the Micro III

Operation Manual to provide Condenser Control.Up to six condenser devices on one dischargelevel can be controlled via output and inputmodules on the Micro III's I/O rack. Condenserdevices can be Water Pumps and Single / Double /Variable Speed Fans (maximum one VariableSpeed Fan).

The Micro III Compressor Panel's CondenserControl operates on the principle of a mechanicaldrum sequencer. In the case of a mechanicaldrum sequencer, the setting of the pressure switchgoverns drum movement. Internal CondenserControl's Setpoint, Next Step, and Previous Stepparameters provide the same functionality.

When a mechanical drum sequencer's motorchanges the drum position, pegs or cams contactswitches to start and stop condenser devices.Condenser Control allows the user to issue acommand to each condenser device for each 'peg'in the drum. The RUN command, for instance,energizes the output to start a single speed fan orwater pump. The LOW command energizes theoutput to run a double speed fan at low speed.AUTO utilizes the internal PID software to control avariable speed fan's speed automatically with

changes in discharge pressure. Any location thatis blank is considered STOP. There can be up to64 'movements of the drum' or Capacity Step. Thecontrol panel will automatically stop incrementingthe Capacity Step when it reaches the last userentry.

For more flexibility than a mechanical drumsequencer, Condenser Control has independenttimers for each Capacity Step. These timersprovide the user with the ability to fine-tune eachCapacity Step's response to a discharge pressurechange. When the actual discharge pressure rises

above the Setpoint plus the Next Step Parameterand the Capacity Step's Next Step Timer expires,the Current Capacity will advance to the next of the64 Capacity Steps. The Previous Step Parameterand Previous Step Timer work in an analogousway to decrease the Current Capacity Step. Whenthe Current Capacity Step changes, the newCapacity Step's Soak Timer must expire before

further 'drum' movement can take place. Thus, theSoak Timer provides time for the condensingsystem to react to a new Capacity Step.

Dual Condenser Setup matrices provide for winter/ summer operation, or the ability to switch deviceroles to equalize runtime and number of starts.

Non-typical system conditions, such as startupafter a prolonged power outage, may require theability to override the condenser's automaticoperation. At power-up, Condenser Control startsat Capacity Step 1, in Auto Mode. The Auto Modewill utilize the parameters and timers to increase ordecrease the Current Capacity Step. The CurrentCapacity Step can be maintained (regardless of

the actual discharge pressure) by pressing the[HOLD] key. Auto Mode can be re-entered bypressing the [AUTO] key. In Auto or Hold mode,the [LOAD] and [UNLOAD] keys will manuallyincrease or decrease the Current Capacity Step byone step.


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Condenser #2 at minimum speed is slightly lesscapacity than Condenser #2 alone (Step 1) atmaximum speed.

Condenser #1Double Speed Fan

Condenser #2Variable Speed Fan

Step 1 AUTO 0%Step 2 LOW AUTO 0%Step 3 HIGH AUTO 0%

Configuration for double speed and variable speedfans, with Condenser #2's capacity approximatelyequal to half of Condenser #1. If Condenser #2 islarger, set the minimum speed for Steps 2 and 3so the combination of Condenser #1 andCondenser #2 at minimum is slightly less capacity

than Condenser #2 at maximum.

KeypadThe key labeled [COND] is used to access theDisplay Groups related to Condenser Control. Toview these displays, press the [COND] key. Thiskey's LED will remain lit.

The [CHANGE DISPLAY] key now moves the userthrough the below Display Groups in sequentialorder (see Displays). Within the Condenser SetupDisplay, the Condenser Detail, Step Delay, andProgram Step Displays can be accessed. To

return to Compressor panel -related displays,press the [COND] key again and its LED will go off.

If a shutdown is annunciated, press the[SHUTDOWNS] key to proceed directly to theCompressor Panel's Shutdowns Display. TheAlarms display is accessed in a similar fashion withthe [ALARMS] key.

While viewing the Condenser Control DisplayGroups, the [AUTO] and [HOLD] will change theCondenser Mode. The [LOAD] and [UNLOAD]keys will increase or decrease the Current

Capacity Step.

DisplaysIn addition to Compressor Panel's displays,several additional displays can be accessedthrough the Micro III's operator interface using the[COND] key for the Condenser Control option.


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Condenser Status

Condenser Setup

Condenser Detail Display

Step Delay Display Program Step Display

Cnd Parameters

Displays - Analog DataThe following entry is now added to theCompressor Panel's Analog Data Display.

Cond Disch Prs -- Gauge pressure measuredusing the Condenser's Discharge Pressuretransducer. This may be the same transduceras the Compressor Discharge Pressure.

Displays - AlarmsThe following alarm annunciations are nowincluded for Internal Condenser Control.

Condenser Matrix # -- The microprocessordetected an out-of-range entry in theCondenser Setup Display. The entry will bedisplayed as 'ERR'. The number following theannunciation indicates which condenserdevice (1 thru 40) has the difficulty. Note thatthis annunciation cannot be cleared until theerror is corrected (valid Condenser Setup entrymade).

Condenser Parameter # -- Themicroprocessor detected a CondenserParameter outside its entry limits. The numberafter the annunciation indicates whichCondenser Parameter is in error. In theCondenser Parameter Display, out-of-rangeparameters will flash until corrected. Note thatthis annunciation cannot be cleared until theerror is corrected (valid Condenser Parameterentered).

Condenser Timer # - The microprocessordetected a Condenser Timer (Next Step,Previous Step, or Soak) outside its entry limits.

The number after the annunciation indicateswhich Capacity Step's Timer is in error. Notethat this annunciation cannot be cleared until

the error is corrected (valid Condenser Timer#entered).

Loss of Cnd Intlk # -- The interlock inputmodule for the indicated condenser deviceremained de-energized for 5 continuousseconds while the device was to operate.

Illegal Cnd Intlk # -- The interlock inputmodule for the indicated condenser deviceremained energized for 5 continuous secondswhile the device was supposed to be idle. Forcondenser devices with interlocks usingHand/Off/Auto switches, the interlock signalmust be broken while in the Hand mode.

Hi Cnd Disch Press -- The condenserdischarge pressure exceeded the Discharge (1or 2) Pressure Upper Condenser Parameter.Annunciation to indicate unexpectedly highdischarge pressure.

Lo Cnd Disch Press -- The condenserdischarge pressure fell below the Discharge (1or 2) Pressure Lower Condenser Parameter.Annunciation to indicate unexpectedly lowdischarge pressure.

Displays - Condenser Status

The Condenser Status Display provides keyinformation about condenser operation. The actual


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discharge pressure, along with units, is displayedprominently on the top half of the display.

Example Condenser Status Display

The Setpoint, Next Step, and Previous StepParameters are shown in the box on the bottomhalf of the display. The Current Capacity Step andCondenser Mode are shown directly above anycurrently active timers. '@Minimum' will bedisplayed when the Current Capacity Step isone (lowest capacity step available). '@Maximum'will be displayed when the Current Capacity Stepreaches the last set of condenser commands inCondenser Setup.

Displays - Condenser SetupThe Condenser Setup Display is a table where theuser describes how the condenser devices shouldinteract to control discharge pressure. The user isable to position the blinking cursor anywhere onthe table using the [], [], [] and [] keys.

The current Capacity Step is indicated by thereverse video block on the appropriate step. Eachcolumn of the table represents a CondenserDevice, like a Single Speed Fan (SSF). Thedescription for the device that the cursor is

currently on is shown on the bottom line of thedisplay. Press the [.CHANGE] key to toggle betweendescription and Condenser Device number.

Example Condenser Setup Display

The Condenser Detail Display may be entered bypositioning the blinking cursor in the first box at the

top of condenser's column and pressing the[ENTER] key. The Condenser Device's TextLabel, Runtime, Number of Starts, and Module

Status will appear. The [] and [] keys are usedto position the cursor. Once the cursor ispositioned, the [EDIT] key is used to initiate thechange of an entry if the control panel is in Servicemode. [EDIT] can be pressed again to abort thechange of an entry. For standard numeric entries,enter the digits on the keypad and press the[ENTER] key to accept the value. If an error ismade during entry, press the [CLEAR] key toremove the previous keystrokes. If the entry is outof range, a 'Minimum=' or 'Maximum=' messagewill appear on the last line of the display and editmode will continue.

Example Condenser Detail Display

Double Speed Fans will have an entry for the delaybetween high and low speed transitions. VariableSpeed Fans will have entries for Proportional,Integral, and Derivative and display the current PIDoutput in percent. To leave the Condenser DeviceDetail Display, press the [ENTER] key while not inedit mode.

The Program Step Display may be entered fromthe main Condenser Setup Display by positioning

the blinking cursor in the column of a particularcondenser device, at the row of a particularCapacity Step, and pressing the [ENTER] key.

The control panel must be in its Service mode.The various condenser device commands will bedisplayed, with the blinking cursor to the left of thecurrent entry. To return to the main CondenserSetup Display, press the [EDIT] key. [] and []

keys may be used to select the desired command,followed by the [ENTER] key. For a Single SpeedFan or Pump, the options to 'Stop' or 'Run' will bepresented. Double Speed Fans have options for'Stop', 'Low' speed, or 'High' speed. Variable

Speed Fans have options for 'Stop', 'Hold' speed ata selectable percentage, or operate in 'Auto' with aminimum speed selectable as a percentage.


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Example Condenser Parameters Display

DISCHARGE PRESSURETwo discharge pressure setpoints areavailable for controlling condensersequencing. Each of the setpoints has its ownset of parameters for complimentary functions.

DISCHARGE (1 OR 2) PRESSURESETPOINT is the discharge pressure to bemaintained. The Next and Previous Stepparameter are added/subtracted from thissetpoint to determine the pressure where'drum' movement is necessary. If theoptional Wet Bulb Discharge PressureControl is enabled, set this entry to the

minimum discharge pressure desired.DISCHARGE (1 OR 2) PRESSUREUPPER is the discharge pressure wherethe 'Hi Cnd Disch Press' Alarmannunciation will be issued. If the optionalWet Bulb Discharge Pressure Control isenabled, this parameter also functions asthe maximum wet bulb discharge pressuresetpoint.DISCHARGE (1 OR 2) PRESSURELOWER sets the discharge pressurewhere the 'Lo Cnd Disch Press' Alarmannunciation will be issued.

DISCHARGE (1 OR 2) PRESSURENEXT STEP is added to the Discharge (1or 2) Pressure Setpoint to set the upperboundary of desired discharge pressure.When discharge pressure rises aboveSetpoint plus Next Step and theappropriate Next Step Timer expires, the

Current Capacity Step will be advanced toincrease condensing capacity.

DISCHARGE (1 OR 2) PRESSUREPREVIOUS STEP is subtracted from theDischarge (1 or 2) Pressure Setpoint to setthe lower boundary of desired dischargepressure. When discharge pressure fallsbelow Setpoint minus Previous Step andthe appropriate Previous Step Timerexpires, the Current Capacity Step will beretarded to decrease condensing capacity.

CONTROL

CONTROL MODE 0=SETPOINT / 1=WETBULB configures condenser operation forfixed setpoint (Setpoint) operation, wherethe active Discharge (1 or 2) PressureSetpoint is used for control. Alternately,the 'floating' (Wet Bulb) discharge setpointcalculated from Wet Bulb Temperaturemay be used. Note that this entry will notbe visible if the optional Wet BulbDischarge Pressure Control is disabled inthe factory-configuration.

CTL PNT 0=DI/1=PNT1/2=PNT2determines which set of DischargePressure Condenser Parameters is usedfor control. With two setpoints, condenseroperation can be optimized for weekdayvs. weekend, for instance. Optionally, afactory-configured digital input(PNT1/PNT2 Cnd Input) may be used tomake the selection (0).

WET BULB SETPOINT SPLIT is usedduring the optional Wet Bulb DischargePressure Control. This parameter addedto the ideal saturated discharge pressure(calculated from the Wet Bulb

Temperature) becomes the 'floating'discharge pressure setpoint. Note that thisentry will not be visible if the optional Wet

Bulb Discharge Pressure Control isdisabled in the factory-configuration.


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Digital I/OThe control panel's digital modules are used to

operate and monitor the system's condenserdevices. These modules are factory-configured for a particular application. Aparticular application may or may not utilize allof these modules. Refer to the supplieddrawings for actual I/O layout. The '#'indicated in the module descriptioncorresponds to the condenser device number.

Cnd # Output A module provides the signal toenergize the starter for a Single Speed Fan,Variable Speed Fan, or Water Pump. For aDouble Speed Fan, this signalshould energize the starter for low speed

operation. This output will be energized whenthe device should operate.

Cnd # Output B module provides the signal toenergize the starter for high speed operationfor a Double Speed Fan. This output will beenergized when the device should operate.

The delay between high and low speeds isprovided within the control panel's logic.

Cnd # Input A module should be wired to theinterlock signal for a Single Speed Fan,Variable Speed Fan, or Water Pump. For aDouble Speed Fan, the low speed interlocksignal should be wired to this input. This input

must be energized when the device operatesto avoid interlock alarms.

Cnd # Input B module should be wired to thehigh speed interlock signal for a Double SpeedFan. This input must be energized when thedevice operates to avoid interlock alarms.

PNT1/PNT2 Cnd Input module is used toswitch between Discharge 1 and Discharge 2setpoints via external control. The ControlMode Condenser Parameter must be set to 0(DI) to utilize this input. De-energize to selectDischarge 1, energize to select Discharge 2.

Condenser Water Pump Lockout Inputmodule should be de-energized to allow waterpumps to operate, or energized to begin alockout cycle. For a specific application, thismodule may be internally linked to additionallogic. See Control - Water Pump Lockout.

Control - Wet BulbDischarge Pressure

Evaporative condensers encounter theirlimitations when the ambient temperature andrelative humidity combine to produce a highwet bulb temperature. Under ideal conditions,the condenser can reject heat from therefrigerant until it reaches the wet bulbtemperature. In practice, lowering systemdischarge pressure during low wet bulbtemperatures can save energy. However,operating more fans and pumps once thedischarge pressure is close to the saturatedpressure (dictated by the wet bulbtemperature) will only waste energy.

Using its optional Wet Bulb Control Mode,Internal Condenser Control can vary thedischarge pressure setpoint automatically,based on the wet bulb temperature. It doesthis by calculating the wet bulb temperaturefrom its relative humidity sensor and ambienttemperature probe, located near thecondensers. Based on the refrigerant selectedin the factory-configuration, the saturateddischarge pressure is then calculated from thewet bulb temperature. The user-adjustableWet Bulb Setpoint Split Condenser Parameteris added to the saturated discharge pressure

to form a 'floating' Wet Bulb DischargePressure Setpoint. To maintain enoughpressure to move liquid refrigerant, theDischarge (1 or 2) Pressure SetpointCondenser Parameter sets the minimum WetBulb Discharge Pressure Setpoint. Finally, theDischarge Pressure Upper parameterestablishes the maximum Wet Bulb DischargePressure Setpoint.

mcp-096 - addendum to micro iii operation for compressor panels with condenser control

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