Marathon Computer AACC 2000 manual Overcurrent protection, Voltage rating, Conductive pollution

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Marathon Monitors Inc.

Overcurrent protection

To protect the internal PCB tracking within the controller against excess currents, the AC power supply to the controller and power outputs must be wired through the fuse or circuit breaker specified in the technical specification.

Voltage rating

The maximum continuous voltage applied between any of the following terminals must not exceed 264Vac:

∙line or neutral to any other connection;

∙relay or triac output to logic, dc or sensor connections;

∙any connection to ground.

The controller should not be wired to a three phase supply with an unearthed star connection. Under fault conditions such a supply could rise above 264Vac with respect to ground and the product would not be safe.

Voltage transients across the power supply connections, and between the power supply and ground, must not exceed 2.5kV. Where occasional voltage transients over 2.5kV are expected or measured, the power installation to both the instrument supply and load circuits should include a transient limiting device.

These units will typically include gas discharge tubes and metal oxide varistors that limit and control voltage transients on the supply line due to lightning strikes or inductive load switching. Devices are available in a range of energy ratings and should be selected to suit conditions at the installation.

Conductive pollution

Electrically conductive pollution must be excluded from the cabinet in which the controller is mounted. For example, carbon dust is a form of electrically conductive pollution. To secure a suitable atmosphere in conditions of conductive pollution, fit an air filter to the air intake of the cabinet. Where condensation is likely, for example at low temperatures, include a thermostatically controlled heater in the cabinet.

Over-temperature protection

When designing any control system it is essential to consider what will happen if any part of the system should fail. In temperature control applications the primary danger is that the heating will remain constantly on. Apart from spoiling the product, this could damage any process machinery being controlled, or even cause a fire.

Reasons why the heating might remain constantly on include:

∙the temperature sensor becoming detached from the process;

∙thermocouple wiring becoming a short circuit;

∙the controller failing with its heating output constantly on;

∙an external valve or contactor sticking in the heating condition;

∙the controller setpoint set too high.

AACC 2000 Carbon

6

Nov. 1, 1997

 

 

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Contents Copyright Marathon Monitors INC Marathon Monitors Inc Mechanical Installation Cleaning SafetyElectrostatic discharge precautions Electromagnetic compatibilityPower Isolation Safety SymbolsWiring PersonnelVoltage rating Over-temperature protectionOvercurrent protection Conductive pollutionInstallation requirements for EMC Grounding of the temperature sensor shieldRouting of wires Environmental ratings Equipment ratingsElectrical safety GeneralMarathon Monitors Inc Installation Outline dimensions Model Outline dimensions Model 2000 controllerController labels To install the controllerIntroduction Unplugging and plugging-in the controllerRear terminal layouts Model Aacc 2000 rear terminal layoutMarathon Monitors Inc Sensor input connections Module 1, 2Two terminal modules SnubbersFour terminal modules COMDual output modules Connections for Process Value 3 in module position Connections for Process Value 2 PV2Communication module Wiring of 2-wire EIA-485 serial communications link EIA-485 wiringMarathon Monitors Inc Operation 26.0 Front Panel LAYOUTsOP2 Button or Name ExplanationOP1 SP2Alarms Basic operationOperating modes Home display Automatic modeOutput power demand Display unitsManual Mode SetpointParameters and HOW to Access Them List header displaysMarathon Monitors Inc Parameter names Parameter displaysTo change the value of a parameter List 1OFFOFF PID PID.1Fact STDPass Name Description Prob Probe list Process Factor Millivolt input OffsetHydrogen or CO constant Name Description DrA.t TunEDrA AdcRES Pid PID listSEt HcbSetpoint list Input listOutput list CmS Comms listInFo Information list Access List FF.OPAlarms Diagnostic alarms Display What it means What to do about it Shows2b Diagnostic alarms Access Levels Access list header Password entryAccess to Read-only Configuration Configuration password Configuration levelLevel selection Returning to Operator Level Setting operator access to a parameterEdit level Hiding or revealing a complete listPromoting a parameter This sheet intentionally left blank Tuning Parameter Code Meaning or FunctionOne-shot Tuning How to tuneTypical automatic tuning cycle Calculation of the cutback valuesAdaptive tune Manual Tuning Setting the cutback values Proceed as followsIntegral action and manual reset Automatic droop compensation AdcName Description Values Mtr Motor list Min Max Default Motorized valve controlAdjusting the minimum on-time ‘mp.t’ Inertia and backlash settingsMarathon Monitors Inc Enable in configuration level Gain schedulingSet the transfer point Configuration Selecting configuration level Press to enter configurationLeaving Configuration Level Changing the passwordsD1SA Enab REULIN SB.OPRely CMSNone DIG YESPMV H2O InSt Instrument configurationName Description Values Meaning SP.FFProcess value config Input configurationCJC Setpoint configuration VAL.LVAL.H Alarm configuration Values Table a Alarm types ValueAlarm Modes Digital input 1 configuration Action on contact closure Digital input 2 configuration Action on contact closureIMP Alarm relay configuration VfltPflt Comms 1 module config Combining several digital events on to one outputModule config 1A b C1 Module 1 configurationCool 2A/b/C Module 2 configuration For ‘id’ = ‘LoG.i’ i.e logic input use the LA Conf’ list onDisplayed value low 3A/b/C Module 3 configuration SELC Module configuration Module configurationPoint Custom Linearisation VAL.1VAL.8 CAL DC Output Calibration Password configurationExit Exit configuration User calibrationUser calibration User Calibration Enable User Calibration EnableCalibration Configuration List Exit configurationOffset calibration Input list headerCalibration type See table on the right for additional parameters Set OffsetTwo-point calibration Displayed ValueAdjust low-point calibration Select Low-point CalibrationAdjust High-point Calibration Select High-point CalibrationCalibration points and Calibration offsets Name Parameter description MeaningParameter Table Default HY1 Ssel FLT3 Marathon Monitors Inc AL1 Module 2A High Value VAL.1 101 Index Two-point calibration User calibration Aacc 2000 Carbon
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