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TC 1818aControl Module

Operating Guide

SWM-015.5

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This guide is intended solely for use by owners of Thermon HeatChekTMheattracing control and monitoring units. This manual describes operation forTC 1818 controllers with firmware released in 2010. Earlier versions of firmwaremay not include all features described in this manual. This manual is consideredproprietary and is protected by copyright. Use by others without expressedwritten consent of Thermon is strictly prohibited.

Thermon 1999, 2005, 2008, 2010

HeatChek and TraceView are tradenames of Thermon Manufacturing Company.

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INDEX

The TC 1818a Module .................................................................... 4

TC 1818a Module Specifications .................................................. 8

Typical HeatChek Control andMonitoring Units ............................................................................ 9

Programming The TC 1818a ........................................................10

The TC 1818a in Operation ..........................................................37

Configuring the TC 1818a for AmbientSensing or Dual RTD Control .......................................................51

Programming and Operating the TC 1818a inan Ambient Sensing Control Mode .............................................55

Programming and Operating the TC 1818a with

Dual Input RTDs for a Single Control Circuit...............................60

Typical Control Applications ........................................................62

Communications ..........................................................................71

Options and Accessories .............................................................72

Help ...............................................................................................73

Attachment A: TC 1818a Command Flowchart

TC 1818aControl Module

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4

TC 1818a Control Module

THE TC 1818a MODULE

The TC 1818a is a microprocessor-based temperature control and monitoring moduledeveloped specifically for heat tracing. The multi-circuit module can provide heat tracingcontrol, digital information display and alarms for high temperature, low temperature, highcurrent, low current, high ground leakage current, circuit fault, and damaged temperaturesensor for up to eighteen heat tracing circuits. Resettable minimum and maximum tem-peratures seen are retained for display on demand.

The TC 1818a module operates independently and can also be connected to a datahighway for remote systems communication functions through a personal computer or a

distributed control system (DCS).

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5

Operating Guide

DATA DISPLAY

The TC 1818a module utilizes a backlit Liquid Crystal Display (LCD) for reporting tem-peratures, currents, and other operating parameters. Alarm LED's in conjunction with theinformation display indicate high temperature, low temperature, high heater current, lowheater current, high ground leakage, sensor fault, and circuit fault alarm status. AdditionalLEDs indicate status of power to the TC 1818a, power to the heat tracing circuits, CPUstatus, and the general controller alarm status.

DATA ENTRY

The TC 1818a has a 16 key "tactile feel" membrane switch keypad which provides formodification (with security key access) of all control parameters as well as permits inquiriesinto the status of any circuit being controlled or monitored.

ALARM RELAY

The TC 1818a module is provided with three independent normally open, close onalarm, solid state alarm relay contacts, rated 1A at 120/240 VAC. The first of theserelays activates in the event of any alarm. The second relay contact activates when any"trip" designated alarms occur. Inverse mode operation on either of these alarms is also

configurable. The third alarm contact provides information regarding the status of internalmodule CPU diagnostics.

CONTROL RELAY

The TC 1818a module can be configured with up to eighteen DC outputs each having a sinkcurrent capability of 100 mA @ 24 VDC for switching up to 18 solid state power relays.

MODULE POWER

The TC 1818a module is convertible from 120 VAC to 208/ to 240 VAC instrument voltage(50 to 60 HZ) from a slide selector switch.

COMMUNICATIONS

Each TC 1818a module is provided with an RS-485 communications port for connectionthrough a two wire twisted shielded pair network into a PC. The Modbus ASCII or RTUprotocol at 9600 baud rate communications streams may also be interfaced into thedistributed control system (DCS).

INPUT/OUTPUT MODULE INTERLINK

Each TC 1818a can be interlinked with up to three six point sensor input modules andthree six circuit power output modules through ribbon cable connections.

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6


The TC 1818a is designed to be an integral part of a HeatChekTMcontrol and monitoringunit. Each unit typically includes one or more TC 1818a modules, power output modules,and sensor input modules, all inter-connecting wiring and ribbon cables, and an electricalenclosure suitable for the environment.

POWER OUTPUT MODULES

Each TC 1818a power output module is configured with six solid state power relays. Thesingle switch SSR30 relays utilized are zero crossing solid state with a single cycle surgecapacity of 600A and a one second overcurrent capacity of 80A. The dual switch SSR15

relays are zero crossing solid state with a single cycle surge capacity of 500A and a onesecond overcurrent capacity of 80A. Design current rating limits for these power outputmodules are determined by the relay type, enclosure size, ambient conditions, and heatsink style (maximum of 30A per single switch relay and 15A for each switch in a dualswitch relay). See Table 1 for details.

Each power output module is provided complete with input/output terminal blocks forup to six heat tracing circuits, ribbon cable up to 15 ft (4.6 m) in length, connectors forlinking to the TC 1818a control module, and a "touch safe" polycarbonate cover mount-

ing assembly.

Table 1: Current Rating

Current ratings are based on outdoor ambients of 104oF (40oC) with solar loading. Contact thefactory for ratings at higher ambient conditions or for ratings in larger enclosure sizes.

The 6SSR30C includes six single switch solid state relays suitable for controlling up to 30 am-peres per switch.

The 6SSR15C includes six dual switch solid state relays suitable for controlling up to 15 amperes

per switch.

Maximum Total Heater CurrentThrough Solid State Relays

Per Enclosure

Enclosure Option

Heat Sink Style C

6SSR30C

Heat Sink Style C

6SSR15C

PS4, SS4 360A 180A

PS5, SS5 576A 288A

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Operating Guide

CONTROL AND MONITORING UNIT

A HeatChek control and monitoring unit utilizing the TC 1818a module, solid state relaypower output modules, sensor input modules, and a NEMA 4 or 4X enclosure is ap-proved/certified for use in Class I, Division 2 Hazardous (classified) as well as Ordinary(non-classified) Locations.

These units include the following warning markings:

This marking intends that the user must disconnect all power sources to the panel priorto servicing.

This marking indicates a location that must be grounded in accordance with local andnational requirements.

CAUTION! CIRCUITS MAY BE ENERGIZED

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8


TC 1818A MODULE SPECIFICATIONS

The TC 1818a module has the general specifications as detailed below:

Control and Monitoring Capacity: Eighteen resistive heat tracing circuits up to 30amps per circuit (depending on switch type)

Module Supply Voltage: 110-120 VAC or 208-240 VAC

Operating Frequency: 50 to 60 Hz Nominal

Power Consumption: 40 watts per TC 1818a module

Module Operating Ambient: -40oF to +140oF (-40oC to +60oC)

Maximum Storage Ambient: 158oF (70oC)

Data Retention: Non volatile EEPROM

Power Clamp Function: Programmable for power levels from 20 to100% maximum power

Input: Up to eighteen 3 wire 100 ohms @ 32oF (0oC)platinum RTD's

Temperature Range (Control): -40oF to 932oF (-40oC to 500oC) with program-mable control band in increments of one degree

Control: On-Off, On-Off with Softstart, Proportional,Proportional Self-Adjust

Module Dimensions: 4-1/2" x 19" x 7-1/2"(114 mm x 482 mm x 191 mm)

Operating Current Alarm High:1.0 to 30.0 ALow:0.0 to 30.0 A

Ground Leakage Alarm/Trip: 30 to 150 mA

Self-Test Frequency: Programmable from 2 to 99 hours

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9

Operating Guide

TYPICAL HEATCHEK CONTROL AND MONITORING UNITS

The TC 1818a is modular in construction and can be configured in a variety of HeatChekcontrol and monitoring units.

INFORMATION

Additional design selection and engineering information may be found inForm T-1008-E.

Specific wiring and equipment arrangement details are usually provided in drawings in-cluded within the HeatChek control and monitoring unit at time of shipment.

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PROGRAMMING THE TC 1818A MODULE

ACCESSING THE PROGRAM MODE

Turn the key to the vertical position and then press the PROG key to enter the program-ming mode.

The TC 1818a will then display the following message:

Then select the desired function key (e.g. MAINTAIN TEMP).

If the function key is not a global function (e.g. CONFIG, DATA HWY, etc.) then the fol-lowing message appears.

Select the desired circuit by pressing the UP or DOWN arrow keys and then pressingthe ENTER key.

In order to set all circuits to a common value, press the UP arrow key until "ALL THE

SAME VALUE" appears.

Press ENTER to globally set a control or operating parameter.

PROGRAM MODE ENABLED

SELECT FUNCTION KEY

PROGRAM CIRCUIT=1

PROGRAM = ALL THE

SAME VALUE

PROG

MAINTAIN

TEMP

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Operating Guide

MAINTAIN TEMPERATURE (PROGRAM MODE)

The following is a typical message which might appear:

Momentarily pressing the UP or DOWN arrow keys will cause the NEW VALUE to change

by 1 degree increments. Holding the key down results in a 10 degree incremental change.If an upper or lower limit is reached, a MAX or MIN message will appear on the secondline. This indicates that either the absolute maximum or minimum value has been reachedor that the value has reached an alarm value.

Once the desired temperature value is set, press the ENTER key to save the value.

The controller will then exit the programming mode and return to the Scan Mode

MAINTAIN TEMP=104F

NEW VALUE=104F

RETURN TO SCAN MODE

MAINTAIN TEMP=104F

NEW VALUE=50F

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HIGH TEMPERATURE ALARM (PROGRAM MODE)

Pressing the HIGH TEMP ALARM function key results in a display message such as thefollowing:

The TC 1818a is set to alarm at 160oF on the current circuit number. Should the controltemperature reach 160oF, the red "ALARM ON" LED on the TC 1818a will begin toflash and the "HIGH TEMP" LED will illuminate when the circuit in alarm appears on theINFORMATION DISPLAY. In addition, the alarm relay contact will close (depending onconfiguration, inverse action may occur).

To change the current value, press the UP or DOWN arrow keys to increase or decreasethe current HIGH TEMP ALARM setpoint.

HIGH TEMP ALARM=160F

NEW VALUE=160F

HIGH

TEMP

ALARM

HIGH TEMP ALARM=160F

NEW VALUE=120F

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Operating Guide

Once the desired temperature value is set, press the ENTER key to save the value.

Next, the following typical message will appear:

At some point since this controller was last reset, the temperature has attained 200F.Press the UP arrow key and ENTER to clear this value and begin anew at the current value.Pressing ENTER or PROG key results in the current value of 200F being retained.

Subsequently, the TC 1818a returns to the Scan Mode.

2 HIGH TEMP SEEN=200F

RESET? (Y/N)

RETURN TO SCAN MODE

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LOW TEMPERATURE ALARM (PROGRAM MODE)

Pressing the LOW TEMP ALARM function key results in a display message such as thefollowing:

The TC 1818a is set to alarm at 50oF on the current circuit number. Should the controltemperature drop to 50oF, the "ALARM ON" LED on the TC 1818a will begin to flash and the"LOW TEMP" LED will illuminate when the circuit in alarm appears on the INFORMATIONDISPLAY. In addition, the alarm relay contact will close (depending on configuration,inverse action may occur).

To change the present value, press the UP or DOWN arrow keys to increase or decreasethe present LOW TEMP ALARM setpoint.Once the desired temperature value is set, pressthe ENTER key to save the value.

LOW

TEMP

ALARM

LOW TEMP ALARM=50F

NEW VALUE=50F

LOW TEMP ALARM=50F

NEW VALUE=35F

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Operating Guide

Next, the following typical message will appear:

At some point since this controller was last reset, the control temperature has dropped to40F. Pressing the ENTER key results in the present value of 40F being retained. Press theUP arrow key and ENTER to clear the stored value and begin anew at the current value.


2 LOW TEMP SEEN=40F

RESET? (Y/N)

RETURN TO SCAN MODE

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HEATER CURRENT (PROGRAM MODE)

Pressing the HEATER CURRENT key (when the TC 1818a is configured with solid staterelays and is set for On-Off with Soft Start, Proportional, or Proportional with Self-Adjust)results in a display message as typically given below:

In this case, the power clamp function is currently in the active or enabled mode. In thismode, the TC 1818a will (through the zero crossing solid state relay provided) use cycleomission techniques to limit the maximum power available to the heater to the value shown(to some value less than the heater would ordinarily provide) at the temperature controlsetpoint. For more details, refer to pages 27 and 28.

Pressing the ENTER key will retain the current mode of operation. Pressing the UP orDOWN arrow key and pressing ENTER will result in the altering of the power percentageand hence result in the limiting of heater power when "ON" at the temperature controlsetpoint.

POWER AT MAINT TEMP=22%NEW VALUE=22%

HEATER

CURRENT

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Operating Guide

The TC 1818a will now return to Scan Mode.

The TC 1818a is provided with a built-in "Soft Start" power up feature when configured inthe On-Off with Soft Start, Proportional, or Proportional Self-Adjust modes. This featurewill utilize cycle omission techniques to ramp up to maximum allowable heater power ina span of approximately 5.5 minutes. This ramp up feature is designed to specifically ad-dress a) cold start power surges associated with self limiting and power limiting heaters,and b) minimize overshoot which may sometimes be present when utilizing high outputheaters in low heat loss applications.

Should the TC 1818a be configured in the On-Off mode, no programming functionssuch as Power Clamping are available. In addition, no "Soft Start" control functions willbe active.

RETURN TO SCAN MODE

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GROUND CURRENT (PROGRAM MODE)

Pressing the GROUND CURRENT function key results in a display message such as thefollowing:

The TC 1818a is set to alarm at heater and associated wiring ground leakage current of40mA on the chosen circuit number. Should the ground leakage value reach 40mA, the"ALARM ON" LED on the TC 1818a will begin to flash and the "GROUND CURRENT"LED will illuminate when the circuit in alarm appears on the INFORMATION DISPLAY. Inaddition, the alarm relay contact will close (depending on configuration, inverse actionmay occur).

To change the value, press the UP or DOWN arrow keys to increase or decrease theGROUND CURRENT ALARM setpoint.

Once the desired new value is set, press the ENTER key to save the value.


GROUND CURRENT ALARM=40mA

NEW VALUE=40mA

GROUND CURRENT ALARM=40mA

NEW VALUE=30mA

GROUND

CURRENT

RETURN TO SCAN MODE

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Operating Guide

HIGH CURRENT ALARM (PROGRAM MODE)

Pressing the HIGH CURRENT ALARM function key results in a display message such asthe following:

The TC 1818a is set to alarm at heater current levels above 20 Amperes on the presentcircuit number. Should the heater current reach 20A, the "ALARM ON" LED on the TC1818a will begin to flash and the "HIGH CURRENT" LED will illuminate when the circuitin alarm appears on the INFORMATION DISPLAY. In addition, the alarm relay contact willclose (depending on configuration, inverse action may occur).

To change the value, press the UP or DOWN arrow keys to increase or decrease the HIGHCURRENT ALARM setpoint.

Once the desired new value is set, press the ENTER key to save the value.Subsequently, the TC 1818a returns to the Scan Mode.

HIGH CURRENT ALARM=20.0A

NEW VALUE=20.0A

HIGH CURRENT ALARM=20.0A

NEW VALUE=25.0A

HIGH

CURRENT

ALARM

RETURN TO SCAN MODE

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LOW CURRENT ALARM (PROGRAM MODE)

Pressing the LOW CURRENT ALARM function key results in a display message such asthe following:

The TC 1818a is set to alarm at heater current levels below 1 Ampere. Should the heatercurrent drop to 1A, the "ALARM ON" LED on the TC 1818a will begin to flash and the "LOWCURRENT" LED will illuminate when the circuit in alarm appears on the INFORMATIONDISPLAY. In addition, the alarm relay contact will close (depending on configuration,inverse action may occur).

To change the value, press the UP or DOWN arrow keys to increase or decrease the LOWCURRENT ALARM setpoint.

Once the desired new value is set, press the ENTER key to save the value.Subsequently, the TC 1818a returns to the Scan Mode.

LOW CURRENT ALARM=1.0A

NEW VALUE=1.0A

RETURN TO SCAN MODE

LOW

CURRENT

ALARM

LOW CURRENT ALARM=1.0A

NEW VALUE=2.0A

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Operating Guide

CONFIG (PROGRAM MODE)

The CONFIG key provides access to setting all global control parameters on the TC 1818a.Pressing the CONFIG key results in the following display prompt:

A "Yes" entry will result in an "Open" relay condition in the event of a RTD sensor failure.Press the UP arrow key for "Yes" or DOWN arrow key for "No." Then press the ENTERkey to save. A "No" entry will result in a "Closed" relay condition in the event of a RTDsensor failure. Subsequently, the TC 1818a follows with the below message on the in-formation display:

The TC 1818a is currently set to NOT trip the heater circuits if a high ground leakagecondition occurs, but rather will only "flash" the "ALARM ON" LED and close the standardalarm relay (open in inverse operation).

To retain the present mode of GROUND CURRENT TRIP operation, press the ENTER key.

Pressing the UP arrow key and ENTER will result in the TC 1818a setting being changedto GROUND CURRENT TRIP ON.

RTD FAULT TURNS CKT ON

CHANGE? (Y/N)

GROUND CURRENT TRIP OFF

CHANGE? (Y/N)

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The TC 1818a will then prompt for the preferred HIGH CURRENT trip setting.

The TC 1818a is currently set to NOT trip the heater circuits if a high heater current alarmcondition occurs, but rather will only "flash" the "ALARM ON" LED and close the standardalarm relay (open in inverse operation).

To retain the present mode of HIGH CURRENT ALARM operation, press the ENTER key.Pressing the UP arrow key and ENTER will result in the TC 1818a setting being changedto HIGH CURRENT TRIP ON.

Once set in this manner, the heater circuits will trip (open heater relay contacts) should aheater current alarm condition occur. The TC 1818a will now require that the operator 1)press the ACKNOWLEDGE key, 2) and the high current alarm condition be cleared priorto automatic control being restored.

The TC 1818a next prompts for the HIGH TEMP ALARM trip setting.

HIGH CURRENT TRIP OFF

CHANGE? (Y/N)

HIGH TEMP TRIP OFF

CHANGE? (Y/N)

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Operating Guide

The TC 1818a is currently set to NOT trip the heater circuits if a high temperature alarmcondition is reached, but rather to only "flash" the "ALARM ON" LED and close the stan-dard alarm relay (open in inverse operation).

To retain the present mode of HIGH TEMP ALARM operation, press the ENTER key.Pressing the UP arrow key and ENTER will result in the TC 1818a setting being changedto HIGH TEMP TRIP ON.

Once set in this manner, the heater circuits will trip (open heater relay contacts) should ahigh temperature alarm condition occur. The TC 1818a will now require that the operator1) press the ACKNOWLEDGE key, 2) and the high current alarm condition be clearedprior to automatic control being restored.

The TC 1818a is provided with On-Off, On-Off with Soft Start, Proportional, andProportional with Self-Adjust control options. The information display next prompts forthe type of control to be selected.

In the ON-OFF control mode, the heater circuit will turn on and off within the programmedcontrol band value.

Press the DOWN arrow and ENTER key to accept this control type. Otherwise, to change

the control type, press the UP arrow key and the ENTER key.

The ON-OFF with SOFT-START option allows the circuit to be gradually powered up byzero crossing cycle omission over a span of approximately 5.5 minutes. Thereafter, theheater circuit will turn on and off within the programmed control band value.

CONTROL = ON/OFF

CHANGE? (Y/N)

CONTROL = SOFT/START

CHANGE? (Y/N)

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To retain the present setting, press the ENTER key. To change the control type, press theUP arrow key and the ENTER key.

The PROPORTIONAL option will now control the heater within the programmed controlband using a proportional algorithm. This algorithm will adjust the power at maintain from20% - 100% (or programed value).


With the SELF-ADJUST feature, the TC 1818a will measure the inherent system error and

will automatically adjust the proportional control parameters to decrease the deviationfrom setpoint to a minimal value.


Note the SELF-ADJUST control option is only available in the SINGLE RTD controllerconfiguration.

CONTROL = PROPORTIONAL

CHANGE? (Y/N)

CONTROL = SELF ADJUST

CHANGE? (Y/N)

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Operating Guide

The TC 1818a offers the option of setting the standard alarm relay switch to be "Closedon Alarm" or "Open on Alarm." The information display next prompts for alarmpreferences.

Press the ENTER key to retain the current setting. Press the UP arrow key and the ENTERkey to change the alarm switch action.

The TC 1818a also offers the option of setting the second TRIP alarm relay switch to be"Closed on Alarm" or "Open on Alarm." The information display next prompts for alarm

preferences.

STD ALARM CLOSED ON ALARM

CHANGE? (Y/N)

TRIP ALARM CLOSED ON ALARM

CHANGE? (Y/N)

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Press the ENTER key to retain the current setting. Press the UP arrow key and the ENTERkey to change the alarm switch action.

The TC 1818a is standardly provided with a SELF TEST function which turns each of theheater circuits "On" and "Off" and looks for the appropriate changes in the relay heatercurrent. During the heater "On" state, the TC 1818a also checks for the presence of both"LOW CURRENT" alarms and "GROUND CURRENT" alarms. The TC 1818a prompts forthe desired settings for the "SELF TEST."

The SELF TEST function is currently disabled. Press the ENTER key to retain this setting.Press the UP arrow key and the ENTER key to change to an automatic SELF TEST intervalfrom 2 to 99 hours.

Subsequently the TC 1818a returns to the Scan Mode.

AUTO SELF TEST = OFF

NEW VALUE = OFF MIN.

RETURN TO SCAN MODE

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Operating Guide

CONTROL BAND (PROGRAM MODE)

Pressing the CONTROL BAND key results in the following display prompt:

If configured in the "On-Off" or "Soft Start" control mode, the TC 1818a will turn on theheater at the maintain temperature setpoint and will turn off at 3oF above this value.

If programmed to operate in the "Proportional Mode", and the "Power at MaintainTemperature" is set at 100%, the TC 1818a will operate at 100% power below the maintaintemperature setpoint and will ramp down in power within the control band and subsequentlyturn off when above the maintenance temperature plus control band.

CONTROL BAND=3oF

NEW VALUE=3oF

Maintain Temp

ON-OFF CONTROL WITH 100% POWER

100%

0%HeaterPower

ControlBand

Maintain Temp

PROPORTIONAL WITH 100% POWER

100%

0%HeaterPower

ControlBand

20%

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If the "Power at Maintain Temperature" has been programmed to some other value (forexample, 62%), the TC 1818a will operate at that power level value at the maintenancetemperature and the control band range will adjust as shown below.

When configured in the "Proportional with Self-Adjust" mode, the TC 1818a will initiallyoperate in the "Proportional Mode" and will subsequently begin to automatically adjustthe slope of the power ramp down. The "Power at Maintain Temperature" will decreaseuntil power output matches the demand.

Maintain Temp

PROPORTIONAL WITH SELF-ADJUST

100%

0%

HeaterPower

ControlBand

55%SteadyState

Maintain Temp

PROPORTIONAL WITH 62% POWER

100%

0%HeaterPower

AdjustedControlBand

20%

62%

ControlBand

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Operating Guide

To retain present control band setting, press the ENTER key. Press the UP or DOWN arrowkey to increase or decrease the control band and press ENTER to save the new value.


RETURN TO SCAN MODE

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HEATER ENABLE (PROGRAM MODE)

The TC 1818a can be factory configured for operation with a variety of pipe sensing, ambi-ent sensing, and RTD assignment configurations.

When programming the HEATER ENABLE settings in one of these control configurations,the following alternate prompt window messages may appear.

For the controller configuration SINGLE RTD INPUTS, the following message will appear

Prompt Window Message Explanation

ENABLED

CHANGE? (Y/N)

The ENABLED prompt will appear on all processsensing circuits. These circuits will turn on whenthe TC 1818a senses a process temperature belowthe maintain temperature setpoint.

The DISABLED prompt allows the option of dis-abling this control circuit for service work.

The FORCE HEATER ON prompt allows the optionof temporarily turning on the heater circuit for

diagnostic purposes.


ENABLED (AMBIENT SENSE)

CHANGE? (Y/N)

ENABLED (PIPE SENSE)

CHANGE? (Y/N)

The ENABLED (AMBIENT SENSE) prompt willappear for all ambient sensed heater circuits.These heater circuits will turn on when the TC

1818a senses an ambient temperature on HeaterCircuit 1 which is below the maintain temperaturesetpoint. Other circuits may appear as ENABLED(PIPE SENSE). In that case, these heater circuitswill turn on when the TC 1818a senses a pipe orheated surface temperature which is below themaintain temperature setpoint. In this controllerconfiguration, CIRCUIT 1 must be set as AMBIENTSENSE.


The FORCE HEATER ON prompt allows the optionof temporarily turning on the heater circuit fordiagnostic purposes.

For the controller configuration 1 AMB / SINGLE RTD INPUTS, the following messagewill appear.

DISABLED

CHANGE? (Y/N)

FORCE HEATER ON?

(Y/N)

DISABLED

CHANGE? (Y/N)

FORCE HEATER ON?

(Y/N)

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Operating Guide

For the controller configuration 2 AMB/ SINGLE RTD INPUTS, the following messagewill appear.



CHANGE? (Y/N)

ENABLED (PIPE SENSE)CHANGE? (Y/N)

The ENABLED (AMBIENT SENSE) prompt willappear for all ambient sensed heater circuits.These heater circuits will turn on when the TC1818a senses an ambient temperature on HeaterCircuit 1 or 2 which is below the maintain tem-perature setpoint. Other circuits may appear

as ENABLED (PIPE SENSE). In that case, theseheater circuits will turn on when the TC 1818asenses a process temperature which is below themaintain temperature setpoint. In this controllerconfiguration, CIRCUIT 1 and 2 must be set asAMBIENT SENSE.



For the controller configuration 1 or 2 RTD INPUTS, the following message will appear.


ENABLED (ONE RTD)

CHANGE? (Y/N)

ENABLED (TWO RTD'S)

CHANGE? (Y/N)

These heater circuit prompts appear when usingdual RTD input controller configurations. In thesecases, the heater circuits will turn on when the TC1818a senses a process temperature (on one orboth RTD sensors) which is below the maintaintemperature setpoint.



DISABLED

CHANGE? (Y/N)

FORCE HEATER ON?

(Y/N)

DISABLED

CHANGE? (Y/N)

FORCE HEATER ON?

(Y/N)

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CHANGE? (Y/N)

ENABLED (TWO RTD'S)

CHANGE? (Y/N)

ENABLED (ONE RTD)

CHANGE? (Y/N)

These prompts appear when using dual RTD processsensing as well as ambient sensing circuit controllerconfigurations. These heater circuits will turn onwhen the TC 1818a senses an ambient temperature(based on the value of the RTD reading in Circuit 1)which is below the maintain temperature setpoint.Other circuit prompts may appear as ENABLED

(ONE RTD or TWO RTD'S). In these cases, theheater circuits will turn on when the TC 1818asenses a process temperature (on one or both RTDsensors) which is below the maintain temperaturesetpoint. Except in the case of CIRCUIT 1 whichmust be AMBIENT SENSE in this factory configu-ration, all other circuits may be set as AMBIENTSENSE or ONE or TWO RTDS control.

The DISABLED prompt allows the option of dis-

abling this control circuit for service work. TheFORCE HEATER ON prompt allows the option oftemporarily turning on the heater circuit for diag-nostic purposes.

ENABLED (AMBIENT SENSED)CHANGE? (Y/N)

ENABLED (ONE RTD)

CHANGE? (Y/N)

ENABLED (TWO RTD)CHANGE? (Y/N)


These prompts appear when using dual RTD process

sensing as well as ambient sensing circuit controllerconfigurations. These heater circuits will turn onwhen the TC 1818a senses an ambient tempera-ture (based on the lower value of the RTD readingin Circuit 1 and 2) which is below the maintaintemperature setpoint. Other circuit prompts mayappear as ENABLED (ONE RTD or TWO RTDS). Inthat case, these heater circuits will turn on whenthe TC 1818a senses a process temperature (on

one or both RTD sensors) which is below the main-tain temperature setpoint. Except in the case ofCIRCUIT 1 and 2 which must be AMBIENT SENSEin this controller configuration, all other circuitsmay be set as AMBIENT SENSE or ONE or TWORTDS control.

For the controller configuration 1 AMB/ 1 or 2 RTD INPUTS, the following message willappear.

For the controller configuration 2 AMB/ 1 or 2 RTD INPUTS, the following message willappear.

DISABLED

CHANGE? (Y/N)

FORCE HEATER ON?

(Y/N)

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Operating Guide

Starting programming by pressing the PROG key.

Subsequently, press the HEATER ENABLE key.

Select the desired circuit by pressing the UP or DOWN arrow keys and then pressingthe ENTER key. Depending on the TC 1818a controller configuration, variations in theprompt message may be seen.

A prompt message as shown below will then appear.

This heater circuit is currently enabled and will turn on when the TC 1818a senses atemperature below the maintain temperature setpoint.

PROGRAM CIRCUIT = 1

HEATERENABLE

ENABLEDCHANGE? (Y/N)


DISABLED

CHANGE? (Y/N)

FORCE HEATER ON?

(Y/N)



PROG

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If the TC 1818a is set for an ambient control configuration the following two enable promptmessages will appear.

Pressing the DOWN arrow key will leave the heater enabled in the ambient sense mode.Press the UP arrow key and the ENTER key.

The TC 1818a will now prompt as follows.

Pressing the DOWN arrow key and the ENTER key will result in enabling the heater as apipe sensing circuit. Pressing the UP arrow key will result in the following new prompt.

Pressing the DOWN arrow key and the ENTER key wil result in disabling the heater cir-cuit and thus result in the removal of external heat from the pipe or heated surface. TheTC 1818a will next prompt as follows.

Press the UP arrow key and the ENTER key to retain this setting. In this operating mode,

the heater will remain ON as long as no programmed alarm limits are exceeded.

Pressing the DOWN arrow and ENTER key will result in the TC 1818a returning to SCANMODE.


CHANGE? (Y/N)

DISABLED

CHANGE? (Y/N)

FORCE HEATER ON?

(Y/N)


CHANGE? (Y/N)

RETURN TO SCAN MODE

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Operating Guide

DATA HIGHWAY (PROGRAM MODE)

Pressing the DATA HIGHWAY key results in the following display prompt:

DATA HIGHWAY=4

NEW VALUE=4

The TC 1818a is currently identified as address number 4. This unique address allows

the data highway communications software to identify the information being sent by thecontroller with a location and heater circuit number.

To retain the present address value, press the ENTER key. Press the UP or DOWN arrow keyto increase or decrease the address value and press ENTER to confirm the new address.

The TC 1818a has the capability to choose the Modbus ASCII or the Modbus RTUprotocols.

Pres the ENTER key to retain the current Modbus protocol. Press the UP arrow key tochange the protocols. Press the ENTER key to confirm the new settings.

MODBUS ASCII

CHANGE? Y/N

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The TC 1818a allows the successive numbering of circuit numbers for a group of modules.As shown below, the TC 1818a prompts for the beginning circuit number for the controlmodule being programmed.

Press the ENTER key to retain the current beginning circuit number. Press the UP arrowkey to arrive at the desired starting point and the ENTER key to confirm the new startingcircuit number.

The TC 1818a then returns to the Scan Mode.

1ST CIRCUIT NUMBER=1

NEW VALUE = 1 MIN.

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Operating Guide

THE TC 1818A IN OPERATION

POWER UP (SCAN MODE)On power up, the TC 1818a will display the following two start-up screen messages.

This prompt message indicates that this TC 1818a controller has been configured to controleighteen heater circuits with eighteen individual RTD inputs. Depending on the TC 1818acontroller configuration, variations in the above message sequence may be seen.

Then the TC 1818a will go into Scan Mode.

THERMON TC 1818a

COPYRIGHT 1995-10

18 RTD INPUTS18 RELAY OUTPUTS

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Once in Scan Mode operation, in the standard factory configuration the TC 1818a willsequentially indicate the temperature reading along with the maintain temperature.

CKT 1 TEMP=51F

MAINTAIN TEMP=50oF

CKT 2 TEMP=122F

MAINTAIN TEMP=120F

CKT 3 TEMP=605F

MAINTAIN TEMP=600F

CKT 4 TEMP=51F

MAINTAIN TEMP=50F

CKT 5 TEMP=122F

MAINTAIN TEMP=120F

CKT 6 TEMP=605F

MAINTAIN TEMP=600F

Upon displaying all temperature information for all configured circuits, the TC 1818a willsubsequently return to the first circuit and repeat the display sequence.

Refer to page 53 for more details on alternate control options and prompt messages.

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Operating Guide

WHEN IN ALARM (SCAN MODE)

Un-Acknowledged Alarms

When an alarm condition occurs, the "ALARM ON" LED will begin to flash, the "ALARMTYPE" LED's will illuminate when the specific circuit in alarm appears on the INFORMATIONDISPLAY, and the standard alarm relay will close.

Acknowledged Alarms

To acknowledge an alarm condition, press the ALARM ACK key. The first alarm conditionwill be indicated in the INFORMATION DISPLAY. Pressing the ALARM ACK key again

will acknowledge this alarm. Repeat this sequence to determine the nature of additionalalarms. Acknowledged alarms are indicated by the suffix Ack appearing when the alarmcondition is displayed. Acknowledged alarms will continue to be displayed until the alarmcondition clears. When all alarms have been acknowledged then the ALARM ON light onthe controller will cease flashing but will stay ON until all alarm conditions have cleared.

Manual Reset

If a TRIP option has been set on a circuit, then all alarms for that circuit must be acknowl-edged before they will clear. When TRIP has been triggered, the alarm for that trip must beacknowledged and the alarm condition must clear before automatic control is restored.

Automatic Reset

When no TRIP options have been set, the alarms will automatically clear when the alarmcondition has cleared.

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ACCESSING DATA (DISPLAY MODE)

Press the MAINTAIN TEMP key to display the Maintain Temperature for all circuits astypically shown.

Press the HEATER CURRENT key to display the Heater Amperage for all enabled circuitsas typically shown.

MAINTAIN TEMP

CIRCUIT 1=50F

MAINTAIN TEMP

CIRCUIT 2=120F

MAINTAIN TEMP

CIRCUIT 3=600F

RETURN TO SCAN MODE

MAINTAIN

TEMP

HEATER

CURRENT

MAINTAIN TEMP

CIRCUIT 4=50F

MAINTAIN TEMP

CIRCUIT 5=120F

MAINTAIN TEMP

CIRCUIT 6=600F

HEATER CURRENT

CIRCUIT 1=1.0A

HEATER CURRENT

CIRCUIT 2=5.0A

HEATER CURRENT

CIRCUIT 3=20.0A

RETURN TO SCAN MODE

HEATER CURRENT

CIRCUIT 4=1.0A

HEATER CURRENT

CIRCUIT 5=5.0A

HEATER CURRENT

CIRCUIT 6=20.0A

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Operating Guide

Press the CONFIG key to display the global settings for all trip and control functions, toview the interval between self tests, and to do a manual SELF TEST on the circuits. Atypical display sequence is shown.

GROUND CURRENT TRIP ON

AUTO SELF TEST ON

INTERVAL 2 HOURS

* NOTE: This information screenonly appears when a circuit isconfigured for dual RTD inputs.

RETURN TO SCAN MODE

CIRCUIT TEST IN PROGRESS

TESTING CIRCUIT #1


TESTING CIRCUIT #2


TESTING CIRCUIT #3


TESTING CIRCUIT #4


TESTING CIRCUIT #5


TESTING CIRCUIT #6

RTD FAULT TURNS CKT OFF

HIGH CURRENT TRIP OFF

HIGH TEMP TRIP ON

CONTROL = ON/OFF

STD ALM CLOSED ON ALARM

TRIP ALM CLOSED ON ALARM

2 RTD ALARM DEADBAND

TEMP = 1F *

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Press the CONTROL BAND key to display the control band settings for all circuits astypically shown.

Subsequently, the TC 1818a returns to Scan Mode.

CONTROL

BAND

CONTROL BAND

CIRCUIT 1=2F

CONTROL BAND

CIRCUIT 2= 3F

CONTROL BAND

CIRCUIT 3= 10F

CONTROL BAND

CIRCUIT 4=2F

CONTROL BAND

CIRCUIT 5=3F

CONTROL BAND

CIRCUIT 6=10F

RETURN TO SCAN MODE

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Operating Guide

Press the GROUND CURRENT key to display ground leakage current from heater andassociated wiring on all circuits as typically shown.

Subsequently the Information display will begin displaying the ground leakage alarm/tripsettings for each circuit.

Upon completion of the display of the ground current alarm/trip values on all circuits, the

TC 1818a returns to Scan Mode.

GROUND

CURRENT

RETURN TO SCAN MODE

GROUND CURRENT

CIRCUIT 1=15mA

GROUND CURRENT

CIRCUIT 2=5mA

GROUND CURRENT

CIRCUIT 3=10mA

GROUND CURRENT

CIRCUIT 4=15mA

GROUND CURRENT

CIRCUIT 5=5mA

GROUND CURRENT

CIRCUIT 6=10mA

GROUND CURRENT ALARM

CIRCUIT 1=40mA


CIRCUIT 2=30mA


CIRCUIT 3=50mA


CIRCUIT 4=40mA


CIRCUIT 5=30mA


CIRCUIT 6=50mA

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Press the HEATER ENABLE key to display if the heater status is set as enabled. The heaterstatus can be enabled, disabled, forced on, or tripped.

Refer to page 54 for more details on alternate HEATER ENABLE prompt messages.


HEATER

ENABLE

RETURN TO SCAN MODE

HEATER

CIRCUIT 1= ENABLED

HEATER

CIRCUIT 2= ENABLED

HEATER

CIRCUIT 3= ENABLED

HEATER

CIRCUIT 4 = ENABLED

HEATER

CIRCUIT 5 = ENABLED

HEATER

CIRCUIT 6 = FORCED ON

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Operating Guide

Press the HIGH TEMP ALARM key to display the High Temperature Alarm Setpoint andHighest Temperature Seen for all circuits as typically shown.

The TC 1818a will then begin to scroll through the highest stored value of temperaturefor each circuit.


RETURN TO SCAN MODE

HIGH TEMP ALARM

CIRCUIT 1=130F

HIGH TEMP ALARM

CIRCUIT 2=20F

HIGH TEMP ALARM

CIRCUIT 3=700F

HIGH TEMP ALARM

CIRCUIT 4=130F

HIGH TEMP ALARM

CIRCUIT 5=200F

HIGH TEMP ALARM

CIRCUIT 6= 700F

HIGH

TEMP

ALARM

HIGH TEMP SEEN

CIRCUIT 1=200F

HIGH TEMP SEEN

CIRCUIT 2=300F

HIGH TEMP SEEN

CIRCUIT 3=700F

HIGH TEMP SEEN

CIRCUIT 4=200F

HIGH TEMP SEEN

CIRCUIT 5=300F

HIGH TEMP SEEN

CIRCUIT 6=700F

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Press the HIGH CURRENT alarm key to display the High Heater Current Alarm setpointas typically shown.

The TC 1818a then returns to Scan Mode.

Press the DATA HWY key to display the Data Highway address setting for the module andcheck the data highway communication status (respectively).

A "COMM STATUS" of IN or OUT denotes direction of the message transmittals (theabsence of IN or OUT indicates that data highway communications link has not been

established). Subsequently, the TC 1818a then returns to Scan Mode.

HIGH

CURRENT

ALARM

HIGH CURRENT ALARM

CIRCUIT 1=5.0A

HIGH CURRENT ALARM

CIRCUIT 2= 10A

HIGH CURRENT ALARM

CIRCUIT 3=30A

HIGH CURRENT ALARM

CIRCUIT 4=5.0A

HIGH CURRENT ALARM

CIRCUIT 5=10A

HIGH CURRENT ALARM

CIRCUIT 6=30A

RETURN TO SCAN MODE

RETURN TO SCAN MODE

DATA

HWY

DATA HIGHWAY ADDRESS=18

COMM STATUS=IN

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Operating Guide

Press the LOW TEMP ALARM key to display the Low Temperature Alarm Setpoint andLowest Temperature Seen for all circuits as typically shown.

The TC 1818a will then begin to scroll through the lowest stored value of temperaturefor each circuit.

Upon completing the display of all the LOW TEMP SEEN data, the TC 1818a returns toScan Mode.

LOW

TEMP

ALARM

LOW TEMP ALARM

CIRCUIT 1=35F

LOW TEMP ALARM

CIRCUIT 2=75F

LOW TEMP ALARM

CIRCUIT 3=450F

LOW TEMP ALARM

CIRCUIT 4=35F

LOW TEMP ALARM

CIRCUIT 5=75F

LOW TEMP ALARM

CIRCUIT 6=450F

LOW TEMP SEEN

CIRCUIT 1=37F

LOW TEMP SEEN

CIRCUIT 2=75F

LOW TEMP SEEN

CIRCUIT 3=550F

LOW TEMP SEEN

CIRCUIT 4=37F

LOW TEMP SEEN

CIRCUIT 5=75F

LOW TEMP SEEN

CIRCUIT 6=550F

RETURN TO SCAN MODE

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Press the LOW CURRENT alarm key to display the Low Heater Current Alarm setpoint forall circuits as typically shown.

After scanning through all circuits, the TC 1818a returns to Scan Mode.

LOW

CURRENT

ALARM

LOW CURRENT ALARM

CIRCUIT 1=1.0A

LOW CURRENT ALARM

CIRCUIT 2=8.0A

LOW CURRENT ALARM

CIRCUIT 3=12.0A

LOW CURRENT ALARM

CIRCUIT 4=1.0A

LOW CURRENT ALARM

CIRCUIT 5=8.0A

LOW CURRENT ALARM

CIRCUIT 6=12.0A

RETURN TO SCAN MODE

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Operating Guide

UNDERSTANDING ALARM CONDITIONS

When temperature related alarm conditions do occur, the below information may be usefulin establishing the cause and appropriate action.

HIGH TEMPERATURE (HIGH TEMP)

Low Limit: Maintain temperature plus control band valueHigh Limit: 1100oF or 600oCRange: 0oF to 1100oF or 0oC to 600oCCause: Sensed temperature exceeds programmed high temperature

alarm setpointControllerAction Taken: Alarm Only or Alarm and Trip Heater (if trip is set)

LOW TEMPERATURE (LOW TEMP)

Low Limit: -40oF or -40oCHigh Limit: Maintain temperature valueRange: -40oF to 1099oF or -40oC to 599oC

Cause: Sensed temperature is below programmed low temperaturealarm setpointController

Action Taken: Alarm Only

RTD FAULT

Cause: RTD resistance not in the 70 to 300 ohms rangeController

Action Taken: Alarm and heater are energized or alarm and heater are turnedoff depending on programming configuration.

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When heater related alarms occur, the below information may be useful in establishing acause and an appropriate action.

HIGH CURRENT (HIGH CURRENT)

Low Limit: Low current alarm valueHigh Limit: 30.0ARange: 1 to 30.0ACause: Heater current is more than high current alarm valueControllerAction Taken: Alarm Only or Alarm and Trip Heater (if trip is set)

LOW CURRENT (LOW CURRENT)

Low Limit: 0.0AHigh Limit: High current alarm valueRange: 0 to 30.0ACause: Heater current is less then low current alarm valueControllerAction Taken: Alarm Only

HIGH GROUND CURRENT (HIGH GND CUR)

Low Limit: 30mAHigh Limit: 150mARange: 30 to 150mACause: An excessive heater/wiring leakage current is presentControllerAction Taken: Alarm Only or Alarm and Trip Heater (if trip is set)

CIRCUIT FAULT (CKT FAULT)

Checks For: Damaged relay or loss of current during "heater on" cycleCause: Relay locked open or closed, breaker off, or heater/wiring disconnectedControllerAction Taken: Alarm Only

POWER OFF

Cause: Loss of voltage to unitControllerAction Taken: NoneReset Procedure: Power off message will clear itself after 30 minutes or can be manually cleared with the ALARM ACK key

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Operating Guide

CONFIGURING THE TC 1818A FOR AMBIENT SENSING OR DUAL RTD CONTROL

The TC 1818a is standardly configured for process sensing with one RTD input assignedto each relay output circuit. The operating descriptions in this manual to this point havecovered using the TC 1818a when set up as a "Standard Control" configuration. Dependingon the firmware level, the TC 1818a can also be factory or field configured for up to fiveother control configurations. The six possible control configurations are identified in thebelow list.

Configuration DescriptionSINGLE RTD INPUTS Conventional process sensing control - one RTD input for

each heat tracing circuit.1 AMB/SINGLE Ambient sensing RTD in Circuit 1 controlling allRTD INPUTS designated ambient sensing circuits with conventional process sensing control on all process sensing circuits (one RTD input for each heat tracing circuit).

2 AMB/SINGLE Ambient sensing RTD's in Circuit 1 and 2 and controllingRTD INPUTS all designated ambient sensing circuits based on the lowest RTD reading with conventional process sensing

control on all process sensing circuits (one RTD input for each heattracing circuit).

1 or 2 RTD INPUTS Single and dual RTD process sensing control - one or two RTD inputs for each heat tracing circuit as designated.

1 AMB/ 1 or 2 RTD INPUTS Ambient sensing RTD in Circuit 1 controlling alldesignated ambient sensing circuits with single or dualRTD process sensing control on all process

sensing circuits.

2 AMB/ 1 or 2 RTD INPUTS Ambient sensing RTD's in Circuit 1 and 2 and controllingl all designated ambient sensing circuits based on the lowest RTD reading with single or dual RTD process sensing control on all process sensing circuits.

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In order to factory or field program the TC 1818a for any configuration other than thestandard SINGLE RTD INPUTS, first momentarily press the DATA HWY key.

Next press and hold the MAINTAIN TEMP key for about 5 seconds.

The following prompt window message will next appear.

Press the CONFIG key.

The current setting for the TC 1818a control configuration will appear.

Press the UP arrow key and ENTER to change or press the DOWN arrow key and ENTERto accept the current configuration and then return to SCAN MODE.

DATA

HWY

RETURN TO SCAN MODE

MAINTAIN

TEMP

ITEM TO CONFIGURE

CONFIG

SINGLE RTD INPUTSCHANGE? (Y/N)

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Operating Guide

It is intended that this configuration setting be set prior to programming in all heat tracingcircuit parameters. If it is necessary to change the settings once the unit is installed in thefield, it is recommended that all heat tracing circuit parameters be entered again.

ALTERNATE CONTROL CONFIGURATIONS IN OPERATION

Information screens will vary slightly depending on which alternate control configurationis enabled. A summary of the alternate message screens which may be seen during theSCAN MODE of operation are listed below:

Where a heater circuit on the TC 1818a controller hasbeen programmed for ambient sensing control opera-tion, this information screen indicates the temperaturebeing read by the RTD on this circuit number and alsoindicates the percentage of power being supplied tothe circuit. When the power clamping function orambient proportional control is utilized, the percentage

"time on" can vary from 100% to as low as 20%.This information screen indicates that the tempera-ture being read by the RTD on this circuit number is51oF and that the heater has been "forced on". Inthe "forced on" mode, the circuit will remain on aslong as no programmed alarm limits are exceeded.This programmed setting is primarily used for fielddiagnostic testing.

Where a heater circuit on the TC 1818a controllerhas been programmed for process temperaturesensing operation, this information screen indicatesthe temperature being read by the RTD on this circuitnumber as well as the actual maintain temperatureprogrammed.

Message Window Description

CKT 1 TEMP = 51F

HEATER POWER= 100% AMB

CKT 1 TEMP = 51F

HEATER FORCED ON

CKT 1 TEMP = 51F MAINTAIN TEMP = 50oF PS

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CKT 1 TEMP = 51F, 53F

HEATER FORCED ON


MAINTAIN TEMP = 50F PS


HEATER POWER=100% AMBWhere a heater circuit on the TC 1818a controller hasbeen programmed for ambient sensing control op-eration with dual RTD inputs, this information screenindicates the temperatures being read by the RTDs onthis circuit number and also indicates the percentageof power being supplied to the circuit. When thepower clamping function or ambient proportionalcontrol is utilized, the percentage "time on" can varyfrom 100% to as low as 20%.

This information screen indicates that the tempera-tures being read by the dual RTDs programmed tosense temperature for this circuit number and that theheater has been "forced on". This program setting isprimarily used for field diagnostic testing.

Where a heater circuit on the TC 1818a controllerhas been programmed for dual RTD process tem-perature sensing operation, this information screenindicates the temperatures being read by the RTDson this circuit number as well as the actual maintaintemperature programmed.

When inquiring as to the heater status (enabled, disabled, forced on, or tripped) by pressingthe HEATER ENABLE key, the following alternate message screens may be seen:

This information screen identifies the Circuit 3 as be-ing enabled as an ambient sensing RTD circuit.

This information screen identifies the Circuit 3 asbeing enabled as a process temperature sensingRTD circuit.

This information screen identifies the Circuit 4 asbeing enabled with one RTD sensor input.

This information screen identifies the Circuit 4 as be-ing enabled with dual RTD sensor inputs.


HEATER

CIRCUIT 3= ENABLED AMB


HEATER

CIRCUIT 3= ENABLED PS

HEATER

CIRCUIT 4= ENABLED 1RTD

HEATER

CIRCUIT 4= ENABLED 2RTD

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Operating Guide

PROGRAMMING AND OPERATING THE TC 1818A IN AN AMBIENT

SENSING CONTROL MODEThe TC 1818a control module should first be configured to allow wide band proportionaltemperature control in ambient sensing control applications.

The simplest controller configuration to implement ambient sensing control are the singleRTD input controller configurations listed below:

When programmed for one of these controller configurations, the TC 1818a controlmodule will accept one ambient sensing RTD input (Circuit 1) or two ambient sensingRTD inputs (Circuit 1 and 2), and will read this input or the lower of the two values into allother ambient sense enabled circuits for control purposes. While most of the TC 1818aoperation in this mode is identical to that previously described (recognizing, of course,that the temperature being acted upon is the ambient value), there are a few differenceswhich are described in the following sections.

1 AMB/ SINGLE RTDINPUTS

2 AMB/ SINGLE RTD

INPUTS

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HEATER ENABLE (PROGRAM MODE)

To program the control mode of each circuit, press sequentially the PROG key and theHEATER ENABLE key. The TC 1818a will prompt for the selection of the desired circuit(or All the Same Value).

Press the UP or DOWN arrow key and ENTER. The TC 1818a will indicate the presentsetting (Ambient Sensing, Pipe Sensing, or Disabled). Press the UP arrow key to changethe value and then the ENTER key to accept the new value.

The configuration restrictions on combinations of process (pipe) sensing and ambientsensing circuits are:

Circuit 1 for single RTD sensor input must be retained as ambient sensing controlcircuit.

Circuit 1 and 2 for dual RTD sensor inputs must be retained as ambient sensingcontrol circuits.

Proportional control mode must be utilized on both ambient and process (pipe)

sensed circuits.

PROGRAM CIRCUIT=1


CHANGE? (Y/N)


CHANGE? (Y/N)

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Operating Guide

MAINTAIN TEMP (PROGRAM MODE)

In order to set the maintain temperature when using ambient sensing control, press thePROG key. The TC 1818a will prompt for the function to program.

Press the MAINTAIN TEMP key. The TC 1818a will next prompt for the selection of thedesired circuit (or All the Same Value).

Press the UP or DOWN arrow key and ENTER. The TC 1818a will prompt for the maintaintemperature as follows:

When in ambient sensing control mode, the minimum ambient temperature should beentered here (this is the 100% heater power value in wide band proportional control). To

change the present maintain temperature value, press the UP or DOWN arrow key untilthe proper value is displayed.

Press the ENTER key to accept the new value. The TC 1818a will then return to the ScanMode operation.


SELECT FUNCTION KEY

PROGRAM CIRCUIT=2

MAINTAIN TEMP=120F

NEW VALUE=120F

MAINTAIN TEMP=120F

NEW VALUE=-20F

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CONTROL BAND (PROGRAM MODE)

In order to set the control range for ambient sensing control, press the PROG key. TheTC 1818a will prompt for the function to program.

Press the CONTROL BAND key. The TC 1818a will next prompt for the selection of thedesired circuit (or All the Same Value).

Press the UP or DOWN arrow key and ENTER. The TC 1818a will prompt for the controlband as follows:


SELECT FUNCTION KEY

PROGRAM CIRCUIT=1

CONTROL BAND=5F

NEW VALUE=5F

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Operating Guide

When in wide band ambient sensing control mode, the control band will be between theminimum ambient temperature (the 100% heater power value) and the ambient temperatureat which power off is to occur (the process fluid minimum desired temperature value).To change the present control band value, press the UP or DOWN arrow key until theproper value is displayed.

Press the ENTER key to accept the new value. Note that with these settings, full powerto the heaters will occur at -20F and power will turn off at 50F. The TC 1818a will thenreturn to the Scan Mode operation.

SCANNING DATA (DISPLAY MODE)

When in the SCAN mode of operation, the TC 1818a will display the following screen onall ambient sensed control circuits in a single RTD controller configuration.

The TC 1818a thus indicates the RTD input temperature which represents the ambienttemperature values measured on Circuit 1 (and Circuit 2 if configured) and is additionallyindicating the power level that this particular circuit is operating at.

Circuit 1 Ambient

Sensing RTDor

Circuit 1and 2Ambient SensingRTD's

CONTROL BAND=5F

NEW VALUE=70F

RETURN TO SCAN MODE

CKT 3 TEMP= -20F, -19F

HEATER POWER=100% AMB

CKT 3 TEMP= -20F

HEATER POWER=100% AMB

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PROGRAMMING AND OPERATING THE TC 1818a WITH DUAL INPUT RTDS

FOR A SINGLE CONTROL CIRCUITThe TC 1818a control module may be factory or field configured to allow for using singleor dual RTD inputs on either ambient sensing or process sensing applications. The fol-lowing three controller configuration options are available for this purpose:

Controller Configuration Application

1or 2 RTD INPUTS Process sensing applications

1AMB/ 1 or 2 RTD INPUTS Process sensing applications and single ambientsensor in first circuit

2 AMB/ 1 or 2 RTD INPUTS Process sensing app lic ations and ambien tsensors in first and second circuit

The above factory configuration options are specifically designed for controlling a heattracing circuit with either single or dual RTD input sensor control circuits. When settingup circuit assignments for these factory configuration types, the heat tracing circuits thatare to be set up with dual RTD's will always be assigned in pairs. That is, the RTD's onCircuit 1 and 2, Circuit 3 and 4, Circuit 5 and 6, and so on should be considered as pairedcircuits. As one example, when dealing with dual RTD's with process sensing, if Circuit6 were to be programmed for a dual RTD input control the TC 1818a controller woulduse the RTD's in Circuit 5 and 6 in controlling the power relay for Circuit 6. The relayassociated with Circuit 5 could be disabled or could be used to control a second pass ofheater if Circuit 5 were also configured as a dual RTD process sensing input (using RTD

5 and RTD 6 for control).

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Operating Guide

As another example, in a "1 AMB/ 1 or 2 RTD INPUTS" controller configuration, if Circuit6 were to be programmed for a dual RTD input control it would again use the RTD's inCircuit 5 and 6 in controlling the power relay for Circuit 6. In this case, however, the relayon Circuit 5 could additionally be used as a control power relay on an ambient sensedcircuit operating based on the RTD input from Circuit 1.

The specific control strategy for a dual RTD control circuit in any of these factory con-figuration types is as follows:

The heat tracing circuit controls off of the lowest RTD reading exceptin the event that a temperature value on either RTD falls within thealarm dead band of the high temperature alarm value. In this event,that RTD will become the controlling temperature reading.

The heat tracing circuit will go into low or high alarm if either RTDreading in the pair exceeds the programmed low or high alarmlimit value.

For more details on setting up a mixed single and dual RTD control mode, refer to Examples5 and 6.

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TYPICAL CONTROL APPLICATIONS

EXAMPLE 1 - AMBIENT SENSING FREEZE PROTECTION -PROPORTIONAL CONTROL WITH SOLID STATE RELAY OUTPUT

When configured with solid state relays, the TC 1818a may be used in ambient sensingwide band proportional control. This method of control is ideal in tracing designs wheresimple ambient sensing RTD's and freeze protection is required. In this mode of control,the TC 1818a will (by cycle omission techniques) proportionally increase the power tothe heat tracing as the ambient temperature drops. A typical application for this type ofcontrol might be the freeze protection of water lines in a water treatment facility. Assume

the following heat tracing operating design Heat Tracing Type: Self-Regulating Parallel Heater Cable Safety Factor: 30% Minimum Ambient: -20F Minimum Water Maintain Temp: 40F

A typical list of the key TC 1818a settings is as given below:

Control Parameter Setting

Controller Configuration 1 AMB/ SINGLE RTD INPUTS Control Method Proportional Maintain Temperature* -20F Percent Power at Maintain Temp. 100% Control Band 60F

* Note that the maintain temperature is the temperature where 100% power issupplied to the heater.

Having set in these values along with appropriate alarm settings, the following control cantypically be achieved.

PipeTemperature

100%

0%-20

Ambient Temperature (degF)

20%Power

40

55

35

75

Pipe

Power

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Operating Guide

EXAMPLE 2 - FOUNDATION HEAVE PROTECTION - PROPORTIONAL WTH SELF-ADJUSTCONTROL WITH SOLID STATE RELAY OUTPUT

Cryogenic vessels and refrigerated rooms often utilize heating systems beneath to preventheaving due to the freezing of the soil/foundation base structure. A typical heat tracingapplication of this type might require an operating tracing design as follows:

Internal Room Temperature: -27F Minimum Maintain Temperature of Soil: 40F Maximum Foundation Temperature: 80F

Heater Cable Type: Constant Wattage Design Safety Margin: 42%

The TC 1818a control module using foundation temperature sensing RTD's in each heatingzone can be typically set at the control settings given below:


Controller Configuration SINGLE RTD INPUTS Control Method Proportional with Self-Adjust

Maintain Temperature 50F Control Band 30F High Alarm Temperature 90F High Temperature Trip On Low Alarm Temperature 38F

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These settings assume the system was designed with a 42% safety margin. By clampingthe power to the 70% value, the heater output should match the heat load. The heatershould be continually operating using cycle omission techniques in a warming mode(and will thus minimize condensation within the heating system). After attaining 50F,the TC 1818a will linearly reduce power (the minimum level of power is 20% after 9Frise) until an equilibrium value between 50F and 80F is obtained. In the unlikely eventthat the 80F setting is exceeded, the control will de-energize the heater circuit. A hightemperature alarm will activate should the RTD sensor detect a temperature above the90F value and the circuit will trip.

Having set in these values as well as the appropriate other limit/control values, the follow-ing typical control can be achieved.

100%

0%

50

Soil Temperature (degF)

20%

Typical ControlledSoil Temperature

Power

70%

805952

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Operating Guide

EXAMPLE 3 - PROCESS TEMPERATURE MAINTENANCE - PROPORTIONAL CONTROLWITH SOLID STATE RELAY OUTPUT

The TC 1818a features the option of proportional control for those applications whereclose temperature control is required on process piping which may have varying processtemperature conditions. A typical heat traced piping application might be a corn syrupviscosity control application. Due to the sensitivity of the syrup to color degradation thesyrup must be maintained below 90F. Typical heat tracing design requirements are listedas follows:

Syrup Maintain Temperature: 80F

Heater Cable Type: Constant Wattage Maximum Syrup Temperature: 90F

The TC 1818a control module utilizing pipe sensing RTD's could be typically set as shownbelow:


Controller Configuration SINGLE RTD INPUTS Control Method Proportional

Maintain Temperature 80F Control Band 10F High Alarm Temperature 90F High Temperature Trip On Low Alarm Temperature 75F Power at Maintain Temperature 100%


100%

0%

80Pipe Temperature (degF)

20%

PipeControlPoint

Power

9083

Controlband

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EXAMPLE 4 - PROCESS TEMPERATURE CONTROL - MECHANICAL RELAYS

Extremely versatile, the TC 1818a can be configured with RM-1 or RM-2 mechanical relayoutput options. This option is often selected in high heat output tracing applications whereeither high current or high voltage switching is required. One such tracing applicationmight be the temperature maintenance of a long sulfur transfer line. Typical tracing designrequirements are listed as follows:

Heater Cable Type: Mineral Insulated Series Cable Voltage Switched: 277 Vac Current Switched: 49A

Sulfur Maintenance Temperature: 282F Sulfur Freeze Point: 260F Sulfur Congeal Point: 320F

The TC 1818a control module with pipe sensing RTD's could be typically as shownbelow:


Controller Configuration SINGLE RTD INPUTS

Control Method On/Off Maintain Temperature 282F Control Band 5F High Alarm Temperature 300F Low Alarm Temperature 260F


290

PipeTemperature(degF)

280

Time

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Operating Guide

EXAMPLE 5 - PROCESS TEMPERATURE CONTROL - SINGLE AND DUAL RTD SENSING

It is sometimes considered advantageous to use dual RTD sensors on a critical heat tracingapplication such as a 50% caustic line. In this way, the power to the heater can be basedon the input of two discrete temperature inputs rather than one. In addition, in the eventof an RTD fault, the operator can be alarmed, the circuit can be acknowledged, and theRTD can be repaired without turning the heat tracing circuit OFF. For this application, thetypical design requirements are as listed below:

Product Maintenance Temperature: 80F Product Freeze Point: 54F

Heater Cable Type: Self Regulating Parallel Cable Maximum Caustic Temperature: 100F

The TC 1818a control module utilizing pipe sensing RTD's could be typically set as indi-cated below:


Controller Configuration 1 or 2 RTD INPUTS Control Method Proportional

Maintain Temperature 80F Control Band 5F High Alarm Temperature 90F High Temperature Trip ON Low Alarm Temperature 60F Power at Maintain Temperature 100%

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Considering that we have only three heat tracing circuits, the TC 1818a would be set upas a six point unit with a controller configuration of "1 or 2 RTD INPUTS".

The heat tracing circuit assignments would be as follows:

Circuit No. Setting

1 Enabled (2 RTD) 2 Disabled 3 Enabled (2 RTD)

4 Disabled 5 Enabled (2 RTD) 6 Disabled

In this case power relays on circuits 2, 4 and 6 will not be connected to the heattracing.

Alternately, in a case where both power relays were to be used to maximize the currentswitching capability, the following circuit assignments could also be used.

Circuit No. Setting

1 Enabled (2 RTD) 2 Enabled (2 RTD) 3 Enabled (2 RTD) 4 Enabled (2 RTD) 5 Enabled (2 RTD) 6 Enabled (2 RTD)

In this circuit assignment, all circuit relays are controlling off of dual RTD inputs. Notethat this configuration is also applicable in center feed arrangements for two heat tracingcircuits running in opposite directions from power.

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Operating Guide

EXAMPLE 6 - PROCESS TEMPERATURE AND AMBIENT SENSING CONTROL - SINGLEAND DUAL RTD SENSING

In many applications there are a variety of control applications. Some may be the criticalapplications such as the 50% caustic in Example 5 and some may be simple water freezeprotection. For this combination application, the typical design requirements are as listedbelow:

50% Caustic Product Maintenance Temperature: 80F Product Freeze Point: 54F

Heater Cable Type: Self Regulating Parallel Cable Maximum Caustic Temperature: 100F Number of Circuits: Two Process Sensing

Water Product Maintenance Temperature: 50F Product Freeze Point: 32F Heater Cable Type: Self Regulating Parallel Cable Number of Circuits: Four Ambient Sensing

The TC 1818a control module utilizing pipe sensing RTD's could be typically set as indi-cated below:


Controller Configuration 1 AMB/ 1 or 2 RTD INPUTS Control Method On-Off Caustic Circuits Maintain Temperature 80F

Control Band 5F High Alarm Temperature 90F High Temperature Trip ON Low Alarm Temperature 60F Water Circuits Maintain Temperature 50F Control Band 5F High Alarm Temperature 120F High Temperature Trip Off

Low Alarm Temperature 40F

Considering that we have only six heat tracing circuits, the TC 1818a would be set up as asix point unit with a controller configuration of "1 AMB/ 1 or 2 RTD INPUTS".

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The heat tracing circuit assignments would be as follows:

Circuit No. Setting

1 Enabled (Ambient Sensed) 2 Enabled (Ambient Sensed) 3 Enabled (2 RTD) 4 Enabled (Ambient Sensed) 5 Enabled (2 RTD) 6 Enabled (Ambient Sensed)

In this case, power relays on circuits 1, 2, 4 and 6 will be controlling ambient sensed cir-cuits based on the RTD input on Circuit 1. Circuit 3 and its power relay will be controllingbased on the RTD inputs from Circuit 3 and Circuit 4. Circuit 5 and its power relay will becontrolling based on the RTD inputs from Circuit 5 and Circuit 6.

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Operating Guide

COMMUNICATIONS

The TC 1818a is standardly provided with an RS485 communications port. This port allowsfor communication through a Modbus ASCII and RTU protocols to a PC workstation orto the facility distributed control system (DCS). Through this communications link, mostof the operating parameters which are programmable at the module can be accessible atthe central PC workstation or DCS system console.

For communications linking between the TC 1818a and a PC workstation, refer to theTraceViewTM Network Explorer Operating Guide.

For communications linking information between the TC 1818a and the facility distributed

control system (DCS), refer to DCS Operations Guide, SWM-008.X.

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OPTIONS AND ACCESSORIES

Thermon can provide a variety of options and accessories to complete the installation.Some typical accessories are listed below.

SW-TVNE

TraceViewTM Network Explorer is a PC-based communications software package developedspecifically for centralized control and monitoring of the various field mounted HeatChekTMunits. TraceView Network Explorer, operating within the Windows environment, allows thechanging of control and alarm setpoints, adjustment of controller operating parameters, and

acknowledgement of all alarms from the control room or motor control center. TraceViewNetwork Explorer permits the viewing of heat tracing isometrics on demand and allowsonline access to heat tracing and controller diagnostic information. Continuous data log-ging and reporting of heat tracing operations/alarm status as well as historical trend datastorage (for later retrieval to spreadsheet or database software) is also provided.

TraceView Network Explorer can be configured for up to sixteen communication ports(with each program instance allowing up to 247 HeatChek control and monitoring units1).Communications can be achieved at distances up to 4000 ft. (1220 m) on the RS485 two

wire twisted shielded communication link.

RTD-100

This three wire resistance temperature detector (RTD) is rated to 500F (260C). Providedwith a standard aluminum termination head, the RTD sensor is insulated with fiberglassand shielded with Type 316 stainless steel housing.

IM-1Interface module for linking RS485 two-wire twisted shielded pair into RS232 port ofPC.

DCALXX

Interposing DC alarm relays can be added for use in ordinary and hazardous locations tointerface to plant DCS systems.

1A minimum of one repeater module is recommended for every thirty-one control andmonitoring modules configured into a data highway.

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Operating Guide

HELP

This HeatChek control and monitoring unit is intended to be used with only the supportof this instruction booklet. If special support needs do arise, Thermon provides localsupport through its area representatives and affiliate companies as well as through a tollfree user support line.

For toll free support dial 1-800-820-HEAT(4328). Information may also be obtained byaccessing the Thermon Website at www.Thermon.com.

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PROG

MAINTAIN TEMPERATURE

MAINTAIN

TEMP ENTER ENTER

PROGRAM

CIRCUIT

NEW

VALUE

PROG

CONTROL BAND

CONTROL

BAND ENTER ENTER

PROGRAM

CIRCUIT

NEW

VALUE

PROG

HIGH TEMPERATURE ALARM

HIGH

TEMP

ALARM

ENTER ENTER

PROGRAM

CIRCUIT

NEW

VALUE

ENTER

RESET HIGH

TEMP SEEN

PROG

LOW TEMPERATURE ALARM

LOW

TEMP

ALARMENTER ENTER

PROGRAM

CIRCUIT

NEW

VALUE

ENTER

RESET LOW

TEMP SEEN

PROG

HIGH CURRENT ALARM

HIGH

CURRENT

ALARMENTER ENTER

PROGRAM

CIRCUIT

NEW

VALUE

PROG

LOW CURRENT ALARM

LOW

CURRENT

ALARMENTER ENTER

PROGRAM

CIRCUIT

NEW

VALUE

ATTACHMENT A: TC 1818A COMMAND FLOWCHART

Note: Security key must be in the vertical position for the TC 1818 to allow programming.

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Operating Guide

ATTACHMENT A: TC 1818A COMMAND FLOWCHART

Note: Security key must be in the vertical position for the TC 1818 to allow programming.

PROG


GROUND

CURRENT ENTER ENTER

PROGRAM

CIRCUIT

NEW

VALUE

PROG

DATA HIGHWAYDATA

HWY ENTER ENTER

PROGRAM

CIRCUIT

NEW

VALUE

CIRCUIT #

REPORTED FAULT

CIRCUIT #

REPORTED FAULT ACK

ALARM

ACK

ALARM ACKNOWLEGE

ALARM

ACK

REPORTED FAULT HASBEEN ACKNOWLEDGED

PROG

HEATER ENABLE/DISABLE

HEATER

ENABLE ENTER

PROGRAM

CIRCUIT

FORCEHEATER ON

CIRCUIT #

ENABLE (PIPE SENSE)

YES YES

NO NO

CIRCUITFORCED ON

CIRCUITENABLED/DISABLED

CHANGE?

CIRCUIT #ENABLE (AMBIENT SENSE)

CIRCUIT #

DISABLE

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THERMON. . . The Heat Tracing Specialists

100 Thermon Dr. P.O. Box 609 San Marcos, TX 78667-0609 Phone: (512) 396-5801Facsimile: (512) 396-3627 1-800-820-HEAThttp://www.thermon.com Part Number: 80505

pn 80505

Documents

control modulethe tc

indexthe tc

data entrythe tc

high temperature

single control circuit

low temperature

typical control applications

dual rtd control