TC 1818a. Operating Guide. Control Module SWM-015.5

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Control Module

Operating Guide

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INDEX

The TC 1818a Module ... 4

TC 1818a Module Specifi cations ... 8

Typical HeatChek Control and

Monitoring Units ... 9

Programming The TC 1818a ... 10

The TC 1818a in Operation ... 37

Confi guring the TC 1818a for Ambient

Sensing or Dual RTD Control ... 51

Programming and Operating the TC 1818a in

an 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

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THE TC 1818a MODULE

The TC 1818a is a microprocessor-based temperature control and monitoring module developed specifi cally for heat tracing. The multi-circuit module can provide heat tracing control, digital information display and alarms for high temperature, low temperature, high current, low current, high ground leakage current, circuit fault, and damaged temperature sensor 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 data highway for remote systems communication functions through a personal computer or a distributed control system (DCS).

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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 the information display indicate high temperature, low temperature, high heater current, low heater current, high ground leakage, sensor fault, and circuit fault alarm status. Additional LED’s indicate status of power to the TC 1818a, power to the heat tracing circuits, CPU status, and the general controller alarm status.

DATA ENTRY

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

ALARM RELAY

The TC 1818a module is provided with three independent normally open, close on alarm, solid state alarm relay contacts, rated 1A at 120/240 VAC. The fi rst of these relays 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 confi gurable. The third alarm contact provides information regarding the status of internal module CPU diagnostics.

CONTROL RELAY

The TC 1818a module can be confi gured with up to eighteen DC outputs each having a sink current 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

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The TC 1818a is designed to be an integral part of a HeatChekTM_{control and monitoring}

unit. 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 electrical enclosure suitable for the environment.

POWER OUTPUT MODULES

Each TC 1818a power output module is confi gured with six solid state power relays. The single switch SSR30 relays utilized are zero crossing solid state with a single cycle surge capacity 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 one second overcurrent capacity of 80A. Design current rating limits for these power output modules are determined by the relay type, enclosure size, ambient conditions, and heat sink style (maximum of 30A per single switch relay and 15A for each switch in a dual switch relay). See Table 1 for details.

Each power output module is provided complete with input/output terminal blocks for up to six heat tracing circuits, ribbon cable up to 15 ft (4.6 m) in length, connectors for linking 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 104o_{F (40}o_{C) with solar loading. Contact the} Maximum Total Heater Current

Through Solid State Relays Per Enclosure Enclosure Option Heat Sink Style C

6SSR30C

Heat Sink Style C 6SSR15C

PS4, SS4 360A 180A

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CONTROL AND MONITORING UNIT

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

These units include the following warning markings:

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

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

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TC 1818A MODULE SPECIFICATIONS

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

Control and Monitoring Capacity: Eighteen resistive heat tracing circuits up to 30

amps 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: -40o_{F to +140}o_{F (-40}o_{C to +60}o_C)

Maximum Storage Ambient: 158o_{F (70}o_C)

Data Retention: Non volatile EEPROM

Power Clamp Function: Programmable for power levels from 20 to

100% maximum power

Input: Up to eighteen 3 wire 100 ohms @ 32o_{F (0}o_C)

platinum RTD's

Temperature Range (Control): -40o_{F to 932}o_{F (-40}o_{C to 500}o_{C) 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"

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TYPICAL HEATCHEK CONTROL AND MONITORING UNITS

The TC 1818a is modular in construction and can be confi gured in a variety of HeatChek control and monitoring units.

INFORMATION

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

Specifi c 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 pressing the ENTER key.

PROGRAM MODE ENABLED SELECT FUNCTION KEY

PROGRAM CIRCUIT=1

PROG

MAINTAIN TEMP

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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 second line. This indicates that either the absolute maximum or minimum value has been reached or 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=104°F NEW VALUE=104°F

RETURN TO SCAN MODE MAINTAIN TEMP=104°F NEW VALUE=50°F

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HIGH TEMPERATURE ALARM (PROGRAM MODE)

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

The TC 1818a is set to alarm at 160o_{F on the current circuit number. Should the control}

temperature reach 160o_{F, the red "ALARM ON" LED on the TC 1818a will begin to}

fl ash and the "HIGH TEMP" LED will illuminate when the circuit in alarm appears on the INFORMATION DISPLAY. In addition, the alarm relay contact will close (depending on confi guration, inverse action may occur).

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

HIGH TEMP ALARM=160°F NEW VALUE=160°F

HIGH TEMP ALARM

HIGH TEMP ALARM=160°F NEW VALUE=120°F

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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 200°F. 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 200°F being retained.

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

2 HIGH TEMP SEEN=200°F RESET? (Y/N)

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LOW TEMPERATURE ALARM (PROGRAM MODE)

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

The TC 1818a is set to alarm at 50o_{F on the current circuit number. Should the control}

temperature drop to 50o_{F, the "ALARM ON" LED on the TC 1818a will begin to fl ash and the}

"LOW TEMP" LED will illuminate when the circuit in alarm appears on the INFORMATION DISPLAY. In addition, the alarm relay contact will close (depending on confi guration, inverse action may occur).

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

LOW TEMP ALARM

LOW TEMP ALARM=50°F NEW VALUE=50°F

LOW TEMP ALARM=50°F NEW VALUE=35°F

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Next, the following typical message will appear:

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

2 LOW TEMP SEEN=40°F RESET? (Y/N)

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HEATER CURRENT (PROGRAM MODE)

Pressing the HEATER CURRENT key (when the TC 1818a is confi gured with solid state relays 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 this mode, the TC 1818a will (through the zero crossing solid state relay provided) use cycle omission 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 control setpoint. For more details, refer to pages 27 and 28.

Pressing the ENTER key will retain the current mode of operation. Pressing the UP or DOWN arrow key and pressing ENTER will result in the altering of the power percentage and hence result in the limiting of heater power when "ON" at the temperature control setpoint.

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

HEATER CURRENT

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The TC 1818a will now return to Scan Mode.

The TC 1818a is provided with a built-in "Soft Start" power up feature when confi gured in the On-Off with Soft Start, Proportional, or Proportional Self-Adjust modes. This feature will utilize cycle omission techniques to ramp up to maximum allowable heater power in a span of approximately 5.5 minutes. This ramp up feature is designed to specifi cally 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 output heaters in low heat loss applications.

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

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GROUND CURRENT (PROGRAM MODE)

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

The TC 1818a is set to alarm at heater and associated wiring ground leakage current of 40mA on the chosen circuit number. Should the ground leakage value reach 40mA, the "ALARM ON" LED on the TC 1818a will begin to fl ash and the "GROUND CURRENT" LED will illuminate when the circuit in alarm appears on the INFORMATION DISPLAY. In addition, the alarm relay contact will close (depending on confi guration, inverse action may occur).

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

GROUND CURRENT ALARM=40mA NEW VALUE=40mA

GROUND CURRENT ALARM=40mA NEW VALUE=30mA

GROUND CURRENT

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HIGH CURRENT ALARM (PROGRAM MODE)

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

The TC 1818a is set to alarm at heater current levels above 20 Amperes on the present circuit number. Should the heater current reach 20A, the "ALARM ON" LED on the TC 1818a will begin to fl ash and the "HIGH CURRENT" LED will illuminate when the circuit in alarm appears on the INFORMATION DISPLAY. In addition, the alarm relay contact will close (depending on confi guration, inverse action may occur).

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

HIGH CURRENT ALARM=20.0A NEW VALUE=20.0A

HIGH CURRENT ALARM=20.0A NEW VALUE=25.0A

HIGH CURRENT

ALARM

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LOW CURRENT ALARM (PROGRAM MODE)

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

The TC 1818a is set to alarm at heater current levels below 1 Ampere. Should the heater current drop to 1A, the "ALARM ON" LED on the TC 1818a will begin to fl ash and the "LOW CURRENT" LED will illuminate when the circuit in alarm appears on the INFORMATION DISPLAY. In addition, the alarm relay contact will close (depending on confi guration, inverse action may occur).

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

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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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 ENTER key to save. A "No" entry will result in a "Closed" relay condition in the event of a RTD sensor 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 leakage condition occurs, but rather will only "fl ash" the "ALARM ON" LED and close the standard alarm 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 changed to 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 alarm condition occurs, but rather will only "fl ash" the "ALARM ON" LED and close the standard alarm 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 changed to HIGH CURRENT TRIP ON.

Once set in this manner, the heater circuits will trip (open heater relay contacts) should a heater 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 prior to 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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The TC 1818a is currently set to NOT trip the heater circuits if a high temperature alarm condition is reached, but rather to only "fl ash" 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 changed to HIGH TEMP TRIP ON.

Once set in this manner, the heater circuits will trip (open heater relay contacts) should a high temperature 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 prior to automatic control being restored.

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

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

CONTROL = ON/OFF CHANGE? (Y/N)

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

The PROPORTIONAL option will now control the heater within the programmed control band using a proportional algorithm. This algorithm will adjust the power at maintain from 20% - 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 deviation from setpoint to a minimal value.

CONTROL = PROPORTIONAL CHANGE? (Y/N)

CONTROL = SELF ADJUST CHANGE? (Y/N)

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

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

The TC 1818a is standardly provided with a SELF TEST function which turns each of the heater circuits "On" and "Off" and looks for the appropriate changes in the relay heater current. 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 for the 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 interval from 2 to 99 hours.

Subsequently the TC 1818a returns to the Scan Mode.

AUTO SELF TEST = OFF NEW VALUE = OFF MIN.

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CONTROL BAND (PROGRAM MODE)

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

If confi gured in the "On-Off" or "Soft Start" control mode, the TC 1818a will turn on the heater at the maintain temperature setpoint and will turn off at 3o_{F above this value.}

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

CONTROL BAND=3o_F

NEW VALUE=3o_F

Maintain Temp

ON-OFF CONTROL WITH 100% POWER

100% 0% Heater Power Control Band Maintain Temp PROPORTIONAL WITH 100% POWER

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

When confi gured in the "Proportional with Self-Adjust" mode, the TC 1818a will initially operate in the "Proportional Mode" and will subsequently begin to automatically adjust the slope of the power ramp down. The "Power at Maintain Temperature" will decrease until power output matches the demand.

Maintain Temp PROPORTIONAL WITH SELF-ADJUST

100%

55%

Maintain Temp PROPORTIONAL WITH 62% POWER

100%

0% Heater

Power AdjustedControl Band 20%

62%

Control Band

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

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HEATER ENABLE (PROGRAM MODE)

The TC 1818a can be factory confi gured for operation with a variety of pipe sensing, ambi-ent sensing, and RTD assignmambi-ent confi gurations.

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

For the controller confi guration SINGLE RTD INPUTS, the following message will appear

Prompt Window Message Explanation

ENABLED CHANGE? (Y/N)

The ENABLED prompt will appear on all process sensing circuits. These circuits will turn on when the TC 1818a senses a process temperature below the 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 option of 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 will appear for all ambient sensed heater circuits. These heater circuits will turn on when the TC 1818a senses an ambient temperature on Heater Circuit 1 which is below the maintain temperature setpoint. Other circuits may appear as ENABLED (PIPE SENSE). In that case, these heater circuits will turn on when the TC 1818a senses a pipe or heated surface temperature which is below the For the controller confi guration 1 AMB / SINGLE RTD INPUTS, the following message will appear.

DISABLED CHANGE? (Y/N)

FORCE HEATER ON? (Y/N)

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For the controller confi guration 2 AMB/ SINGLE RTD INPUTS, the following message will appear.

The ENABLED (AMBIENT SENSE) prompt will appear for all ambient sensed heater circuits. These heater circuits will turn on when the TC 1818a senses an ambient temperature on Heater Circuit 1 or 2 which is below the maintain tem-perature setpoint. Other circuits may appear as ENABLED (PIPE SENSE). In that case, these heater circuits will turn on when the TC 1818a senses a process temperature which is below the maintain temperature setpoint. In this controller confi guration, CIRCUIT 1 and 2 must be set as AMBIENT SENSE.

For the controller confi guration 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 using dual RTD input controller confi gurations. In these cases, the heater circuits will turn on when the TC 1818a senses a process temperature (on one or both RTD sensors) which is below the maintain temperature setpoint.

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Prompt Window Message Explanation ENABLED (AMBIENT SENSE)

CHANGE? (Y/N)

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

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

These prompts appear when using dual RTD process sensing as well as ambient sensing circuit controller confi gurations. These heater circuits will turn on when 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, the heater circuits will turn on when the TC 1818a senses a process temperature (on one or both RTD sensors) which is below the maintain temperature setpoint. Except in the case of CIRCUIT 1 which must be AMBIENT SENSE in this factory confi gu-ration, all other circuits may be set as AMBIENT SENSE or ONE or TWO RTDS control.

The DISABLED prompt allows the option of dis-abling this control circuit for service work. The FORCE HEATER ON prompt allows the option of temporarily turning on the heater circuit for diag-nostic purposes.

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

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

These prompts appear when using dual RTD process sensing as well as ambient sensing circuit controller confi gurations. These heater circuits will turn on when the TC 1818a senses an ambient tempera-ture (based on the lower value of the RTD reading in Circuit 1 and 2) which is below the maintain temperature setpoint. Other circuit prompts may For the controller confi guration 1 AMB/ 1 or 2 RTD INPUTS, the following message will appear.

For the controller confi guration 2 AMB/ 1 or 2 RTD INPUTS, the following message will appear.

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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 pressing the ENTER key. Depending on the TC 1818a controller confi guration, variations in the prompt message may be seen.

PROGRAM CIRCUIT = 1

HEATER ENABLE

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If the TC 1818a is set for an ambient control confi guration the following two enable prompt messages 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 a pipe 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. The TC 1818a will next prompt as follows.

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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 identifi ed as address number 4. This unique address allows the data highway communications software to identify the information being sent by the controller with a location and heater circuit number.

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

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

Pres the ENTER key to retain the current Modbus protocol. Press the UP arrow key to change the protocols. Press the ENTER key to confi rm 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 control module being programmed.

Press the ENTER key to retain the current beginning circuit number. Press the UP arrow key to arrive at the desired starting point and the ENTER key to confi rm the new starting circuit number.

The TC 1818a then returns to the Scan Mode.

1ST CIRCUIT NUMBER=1 NEW VALUE = 1 MIN.

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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 confi gured to control eighteen heater circuits with eighteen individual RTD inputs. Depending on the TC 1818a controller confi guration, variations in the above message sequence may be seen. Then the TC 1818a will go into Scan Mode.

18 RTD INPUTS 18 RELAY OUTPUTS

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Once in Scan Mode operation, in the standard factory confi guration the TC 1818a will sequentially indicate the temperature reading along with the maintain temperature.

CKT 1 TEMP=51°F MAINTAIN TEMP=50o_F CKT 2 TEMP=122°F MAINTAIN TEMP=120°F CKT 3 TEMP=605°F MAINTAIN TEMP=600°F CKT 4 TEMP=51°F MAINTAIN TEMP=50°F CKT 5 TEMP=122°F MAINTAIN TEMP=120°F CKT 6 TEMP=605°F MAINTAIN TEMP=600°F

Upon displaying all temperature information for all confi gured circuits, the TC 1818a will subsequently return to the fi rst circuit and repeat the display sequence.

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WHEN IN ALARM (SCAN MODE)

Un-Acknowledged Alarms

When an alarm condition occurs, the "ALARM ON" LED will begin to fl ash, the "ALARM TYPE" LED's will illuminate when the specifi c circuit in alarm appears on the INFORMATION DISPLAY, and the standard alarm relay will close.

Acknowledged Alarms

To acknowledge an alarm condition, press the ALARM ACK key. The fi rst alarm condition will be indicated in the INFORMATION DISPLAY. Pressing the ALARM ACK key again will acknowledge this alarm. Repeat this sequence to determine the nature of additional alarms. Acknowledged alarms are indicated by the suffi x “Ack” appearing when the alarm condition is displayed. Acknowledged alarms will continue to be displayed until the alarm condition clears. When all alarms have been acknowledged then the ALARM ON light on the controller will cease fl ashing 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 be acknowledged 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 alarm condition has cleared.

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ACCESSING DATA (DISPLAY MODE)

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

Press the HEATER CURRENT key to display the Heater Amperage for all enabled circuits as typically shown. MAINTAIN TEMP CIRCUIT 1=50°F MAINTAIN TEMP CIRCUIT 2=120°F MAINTAIN TEMP CIRCUIT 3=600°F

RETURN TO SCAN MODE

MAINTAIN TEMP HEATER CURRENT MAINTAIN TEMP CIRCUIT 4=50°F MAINTAIN TEMP CIRCUIT 5=120°F MAINTAIN TEMP CIRCUIT 6=600°F HEATER CURRENT CIRCUIT 1=1.0A HEATER CURRENT HEATER CURRENT CIRCUIT 4=1.0A HEATER CURRENT

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

GROUND CURRENT TRIP ON

AUTO SELF TEST ON INTERVAL 2 HOURS

* NOTE: This information screen only appears when a circuit is confi gured for dual RTD inputs.

CIRCUIT TEST IN PROGRESS TESTING CIRCUIT #1

CIRCUIT TEST IN PROGRESS TESTING CIRCUIT #4 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 = 1°F *

(42)

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

Subsequently, the TC 1818a returns to Scan Mode.

CONTROL BAND CONTROL BAND CIRCUIT 1=2°F CONTROL BAND CIRCUIT 2= 3°F CONTROL BAND CIRCUIT 3= 10°F CONTROL BAND CIRCUIT 4=2°F CONTROL BAND CIRCUIT 5=3°F CONTROL BAND CIRCUIT 6=10°F

(43)

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

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

GROUND CURRENT 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

(44)

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

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

Subsequently, the TC 1818a returns to Scan Mode.

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

(45)

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

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

HIGH TEMP ALARM CIRCUIT 1=130°F

HIGH TEMP ALARM CIRCUIT 2=20°F HIGH TEMP ALARM CIRCUIT 3=700°F

HIGH TEMP ALARM CIRCUIT 4=130°F

HIGH TEMP ALARM CIRCUIT 5=200°F HIGH TEMP ALARM CIRCUIT 6= 700°F HIGH

TEMP ALARM

HIGH TEMP SEEN CIRCUIT 1=200°F HIGH TEMP SEEN CIRCUIT 2=300°F

HIGH TEMP SEEN CIRCUIT 3=700°F

HIGH TEMP SEEN CIRCUIT 4=200°F

HIGH TEMP SEEN CIRCUIT 5=300°F HIGH TEMP SEEN CIRCUIT 6=700°F

(46)

Press the HIGH CURRENT alarm key to display the High Heater Current Alarm setpoint as 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 and check the data highway communication status (respectively).

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

DATA HWY

DATA HIGHWAY ADDRESS=18 COMM STATUS=IN

(47)

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

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

LOW TEMP ALARM

LOW TEMP ALARM CIRCUIT 1=35°F

LOW TEMP ALARM CIRCUIT 2=75°F LOW TEMP ALARM CIRCUIT 3=450°F

LOW TEMP ALARM CIRCUIT 4=35°F

LOW TEMP ALARM CIRCUIT 5=75°F LOW TEMP ALARM CIRCUIT 6=450°F

LOW TEMP SEEN CIRCUIT 1=37°F

LOW TEMP SEEN CIRCUIT 2=75°F LOW TEMP SEEN CIRCUIT 3=550°F

LOW TEMP SEEN CIRCUIT 4=37°F

LOW TEMP SEEN CIRCUIT 5=75°F LOW TEMP SEEN CIRCUIT 6=550°F

(48)

Press the LOW CURRENT alarm key to display the Low Heater Current Alarm setpoint for all 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

(49)

UNDERSTANDING ALARM CONDITIONS

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

HIGH TEMPERATURE (HIGH TEMP)

Low Limit: Maintain temperature plus control band value High Limit: 1100o_{F or 600}o_C

Range: 0o_{F to 1100}o_{F or 0}o_{C to 600}o_C

Cause: Sensed temperature exceeds programmed high temperature alarm setpoint

Controller

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

LOW TEMPERATURE (LOW TEMP)

Low Limit: -40o_{F or -40}o_C

High Limit: Maintain temperature value Range: -40o_{F to 1099}o_{F or -40}o_{C to 599}o_C

Cause: Sensed temperature is below programmed low temperature alarm setpoint

Controller

Action Taken: Alarm Only

RTD FAULT

Cause: RTD resistance not in the 70 to 300 ohms range Controller

Action Taken: Alarm and heater are energized or alarm and heater are turned off depending on programming confi guration.

(50)

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

HIGH CURRENT (HIGH CURRENT)

Low Limit: Low current alarm value High Limit: 30.0A

Range: 1 to 30.0A

Cause: Heater current is more than high current alarm value Controller

LOW CURRENT (LOW CURRENT)

Low Limit: 0.0A

High Limit: High current alarm value Range: 0 to 30.0A

Cause: Heater current is less then low current alarm value Controller

Action Taken: Alarm Only

HIGH GROUND CURRENT (HIGH GND CUR)

Low Limit: 30mA High Limit: 150mA Range: 30 to 150mA

Cause: An excessive heater/wiring leakage current is present Controller

CIRCUIT FAULT (CKT FAULT)

Checks For: Damaged relay or loss of current during "heater on" cycle Cause: Relay locked open or closed, breaker off, or heater/wiring disconnected

(51)

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

The TC 1818a is standardly confi gured for process sensing with one RTD input assigned to each relay output circuit. The operating descriptions in this manual to this point have covered using the TC 1818a when set up as a "Standard Control" confi guration. Depending on the fi rmware level, the TC 1818a can also be factory or fi eld confi gured for up to fi ve other control confi gurations. The six possible control confi gurations are identifi ed in the below list.

Confi guration Description

SINGLE RTD INPUTS Conventional process sensing control - one RTD input for each heat tracing circuit.

1 AMB/SINGLE Ambient sensing RTD in Circuit 1 controlling all RTD 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 controlling RTD 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 all

designated ambient sensing circuits with single or dual RTD 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.

(52)

In order to factory or fi eld program the TC 1818a for any confi guration other than the standard SINGLE RTD INPUTS, fi rst 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 confi guration will appear.

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

DATA HWY MAINTAIN TEMP ITEM TO CONFIGURE CONFIG SINGLE RTD INPUTS CHANGE? (Y/N)

(53)

It is intended that this confi guration setting be set prior to programming in all heat tracing circuit parameters. If it is necessary to change the settings once the unit is installed in the fi eld, 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 confi guration is enabled. A summary of the alternate message screens which may be seen during the SCAN MODE of operation are listed below:

Where a heater circuit on the TC 1818a controller has been programmed for ambient sensing control opera-tion, this information screen indicates the temperature being read by the RTD on this circuit number and also indicates the percentage of power being supplied to the circuit. When the power clamping function or ambient 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 is 51o_{F and that the heater has been "forced on". In}

the "forced on" mode, the circuit will remain on as long as no programmed alarm limits are exceeded. This programmed setting is primarily used for fi eld diagnostic testing.

Where a heater circuit on the TC 1818a controller has been programmed for process temperature sensing operation, this information screen indicates the temperature being read by the RTD on this circuit number as well as the actual maintain temperature

Message Window Description

CKT 1 TEMP = 51°F

HEATER POWER= 100% AMB

CKT 1 TEMP = 51°F

HEATER FORCED ON

(54)

CKT 1 TEMP = 51°F, 53°F HEATER FORCED ON

CKT 1 TEMP = 51°F, 53°F MAINTAIN TEMP = 50°F PS CKT 1 TEMP = 51°F, 53°F HEATER POWER=100% AMB

Where a heater circuit on the TC 1818a controller has been programmed for ambient sensing control op-eration with dual RTD inputs, this information screen indicates the temperatures being read by the RTDs on this circuit number and also indicates the percentage of power being supplied to the circuit. When the power clamping function or ambient proportional control is utilized, the percentage "time on" can vary from 100% to as low as 20%.

This information screen indicates that the tempera-tures being read by the dual RTDs programmed to sense temperature for this circuit number and that the heater has been "forced on". This program setting is primarily used for fi eld diagnostic testing.

Where a heater circuit on the TC 1818a controller has been programmed for dual RTD process tem-perature sensing operation, this information screen indicates the temperatures being read by the RTDs on this circuit number as well as the actual maintain temperature programmed.

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

This information screen identifi es the Circuit 3 as be-ing enabled as an ambient sensbe-ing RTD circuit.

This information screen identifi es the Circuit 3 as being enabled as a process temperature sensing

HEATER

CIRCUIT 3= ENABLED AMB

HEATER

(55)

PROGRAMMING AND OPERATING THE TC 1818A IN AN AMBIENT

SENSING CONTROL MODE

The TC 1818a control module should fi rst be confi gured to allow wide band proportional temperature control in ambient sensing control applications.

The simplest controller confi guration to implement ambient sensing control are the single RTD input controller confi gurations listed below:

When programmed for one of these controller confi gurations, the TC 1818a control module will accept one ambient sensing RTD input (Circuit 1) or two ambient sensing RTD inputs (Circuit 1 and 2), and will read this input or the lower of the two values into all other ambient sense enabled circuits for control purposes. While most of the TC 1818a operation 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 differences which are described in the following sections.

1 AMB/ SINGLE RTD INPUTS

2 AMB/ SINGLE RTD INPUTS

(56)

HEATER ENABLE (PROGRAM MODE)

To program the control mode of each circuit, press sequentially the PROG key and the HEATER 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 present setting (Ambient Sensing, Pipe Sensing, or Disabled). Press the UP arrow key to change the value and then the ENTER key to accept the new value.

The confi guration restrictions on combinations of process (pipe) sensing and ambient sensing circuits are:

• Circuit 1 for single RTD sensor input must be retained as ambient sensing control circuit.

• Circuit 1 and 2 for dual RTD sensor inputs must be retained as ambient sensing

PROGRAM CIRCUIT=1

(57)

MAINTAIN TEMP (PROGRAM MODE)

In order to set the maintain temperature when using ambient sensing control, press the PROG 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 the desired circuit (or All the Same Value).

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

When in ambient sensing control mode, the minimum ambient temperature should be entered 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 until the proper value is displayed.

PROGRAM CIRCUIT=2

MAINTAIN TEMP=120°F NEW VALUE=120°F

MAINTAIN TEMP=120°F NEW VALUE=-20°F

(58)

CONTROL BAND (PROGRAM MODE)

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

Press the CONTROL BAND key. The TC 1818a will next 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 prompt for the control band as follows:

PROGRAM CIRCUIT=1

CONTROL BAND=5°F NEW VALUE=5°F

(59)

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

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

SCANNING DATA (DISPLAY MODE)

When in the SCAN mode of operation, the TC 1818a will display the following screen on all ambient sensed control circuits in a single RTD controller confi guration.

Circuit 1 Ambient Sensing RTD or Circuit 1and 2 Ambient Sensing CONTROL BAND=5°F NEW VALUE=70°F

RETURN TO SCAN MODE

CKT 3 TEMP= -20°F, -19°F HEATER POWER=100% AMB CKT 3 TEMP= -20°F HEATER POWER=100% AMB

(60)

PROGRAMMING AND OPERATING THE TC 1818a WITH DUAL INPUT RTDS

FOR A SINGLE CONTROL CIRCUIT

The TC 1818a control module may be factory or fi eld confi gured to allow for using single or dual RTD inputs on either ambient sensing or process sensing applications. The fol-lowing three controller confi guration options are available for this purpose:

Controller Confi guration Application

1or 2 RTD INPUTS Process sensing applications

1AMB/ 1 or 2 RTD INPUTS Process sensing applications and single ambient sensor in fi rst circuit

2 AMB/ 1 or 2 RTD INPUTS Process sensing applications and ambient sensors in fi rst and second circuit

The above factory confi guration options are specifi cally designed for controlling a heat tracing circuit with either single or dual RTD input sensor control circuits. When setting up circuit assignments for these factory confi guration types, the heat tracing circuits that are to be set up with dual RTD's will always be assigned in pairs. That is, the RTD's on Circuit 1 and 2, Circuit 3 and 4, Circuit 5 and 6, and so on should be considered as paired circuits. As one example, when dealing with dual RTD's with process sensing, if Circuit 6 were to be programmed for a dual RTD input control the TC 1818a controller would use the RTD's in Circuit 5 and 6 in controlling the power relay for Circuit 6. The relay associated with Circuit 5 could be disabled or could be used to control a second pass of heater if Circuit 5 were also confi gured as a dual RTD process sensing input (using RTD 5 and RTD 6 for control).

(61)

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

The specifi c control strategy for a dual RTD control circuit in any of these factory con-fi guration types is as follows:

The heat tracing circuit controls off of the lowest RTD reading except in the event that a temperature value on either RTD falls within the alarm 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 RTD reading in the pair exceeds the programmed low or high alarm limit value.

For more details on setting up a mixed single and dual RTD control mode, refer to Examples 5 and 6.

(62)

TYPICAL CONTROL APPLICATIONS

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

When confi gured with solid state relays, the TC 1818a may be used in ambient sensing wide band proportional control. This method of control is ideal in tracing designs where simple 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 to the heat tracing as the ambient temperature drops. A typical application for this type of control 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: -20°F Minimum Water Maintain Temp: 40°F A typical list of the key TC 1818a settings is as given below:

Control Parameter Setting

Controller Confi guration 1 AMB/ SINGLE RTD INPUTS Control Method Proportional

Maintain Temperature* -20°F Percent Power at Maintain Temp. 100% Control Band 60°F

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

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

Pipe Temperature

100% Pipe

(63)

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

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

Internal Room Temperature: -27°F Minimum Maintain Temperature

of Soil: 40°F Maximum Foundation Temperature: 80°F

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

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

Controller Confi guration SINGLE RTD INPUTS Control Method Proportional with Self-Adjust Maintain Temperature 50°F

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

(64)

These settings assume the system was designed with a 42% safety margin. By clamping the power to the 70% value, the heater output should match the heat load. The heater should be continually operating using cycle omission techniques in a warming mode (and will thus minimize condensation within the heating system). After attaining 50°F, the TC 1818a will linearly reduce power (the minimum level of power is 20% after 9°F rise) until an equilibrium value between 50°F and 80°F is obtained. In the unlikely event that the 80°F setting is exceeded, the control will de-energize the heater circuit. A high temperature alarm will activate should the RTD sensor detect a temperature above the 90°F 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 Controlled Soil Temperature Power 70% 80 59 52

(65)

EXAMPLE 3 - PROCESS TEMPERATURE MAINTENANCE - PROPORTIONAL CONTROL WITH SOLID STATE RELAY OUTPUT

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

Syrup Maintain Temperature: 80°F

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

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

Controller Confi guration SINGLE RTD INPUTS Control Method Proportional Maintain Temperature 80°F Control Band 10°F High Alarm Temperature 90°F High Temperature Trip On Low Alarm Temperature 75°F Power at Maintain Temperature 100%

100% _Pipe Control Power

(66)

EXAMPLE 4 - PROCESS TEMPERATURE CONTROL - MECHANICAL RELAYS

Extremely versatile, the TC 1818a can be confi gured with RM-1 or RM-2 mechanical relay output options. This option is often selected in high heat output tracing applications where either high current or high voltage switching is required. One such tracing application might be the temperature maintenance of a long sulfur transfer line. Typical tracing design requirements are listed as follows:

Heater Cable Type: Mineral Insulated Series Cable Voltage Switched: 277 Vac

Current Switched: 49A Sulfur Maintenance Temperature: 282°F Sulfur Freeze Point: 260°F Sulfur Congeal Point: 320°F

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

Controller Confi guration SINGLE RTD INPUTS Control Method On/Off

Maintain Temperature 282°F Control Band 5°F

High Alarm Temperature 300°F Low Alarm Temperature 260°F

290 Pipe Temperature (degF)

(67)

EXAMPLE 5 - PROCESS TEMPERATURE CONTROL - SINGLE AND DUAL RTD SENSING It is sometimes considered advantageous to use dual RTD sensors on a critical heat tracing application such as a 50% caustic line. In this way, the power to the heater can be based on the input of two discrete temperature inputs rather than one. In addition, in the event of an RTD fault, the operator can be alarmed, the circuit can be acknowledged, and the RTD can be repaired without turning the heat tracing circuit OFF. For this application, the typical design requirements are as listed below:

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

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

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

Controller Confi guration 1 or 2 RTD INPUTS Control Method Proportional Maintain Temperature 80°F Control Band 5°F

High Alarm Temperature 90°F High Temperature Trip ON Low Alarm Temperature 60°F Power at Maintain Temperature 100%

(68)

Considering that we have only three heat tracing circuits, the TC 1818a would be set up as a six point unit with a controller confi guration 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 heat tracing.

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

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. Note that this confi guration is also applicable in center feed arrangements for two heat tracing circuits running in opposite directions from power.

(69)

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

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

50% Caustic

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

Number of Circuits: Two Process Sensing

Water

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 Confi guration 1 AMB/ 1 or 2 RTD INPUTS Control Method On-Off

Caustic Circuits

Maintain Temperature 80°F Control Band 5°F

High Alarm Temperature 90°F High Temperature Trip ON Low Alarm Temperature 60°F Water Circuits

(70)

The heat tracing circuit assignments would be as follows:

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 controlling based on the RTD inputs from Circuit 3 and Circuit 4. Circuit 5 and its power relay will be controlling based on the RTD inputs from Circuit 5 and Circuit 6.

(71)

COMMUNICATIONS

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

For communications linking between the TC 1818a and a PC workstation, refer to the TraceViewTM _{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 developed specifi cally for centralized control and monitoring of the various fi eld mounted HeatChekTM units. TraceView Network Explorer, operating within the Windows environment, allows the changing of control and alarm setpoints, adjustment of controller operating parameters, and acknowledgement of all alarms from the control room or motor control center. TraceView Network Explorer permits the viewing of heat tracing isometrics on demand and allows online 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 data storage (for later retrieval to spreadsheet or database software) is also provided. TraceView Network Explorer can be confi gured 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 500°F (260°C). Provided with a standard aluminum termination head, the RTD sensor is insulated with fi berglass and shielded with Type 316 stainless steel housing.

IM-1

Interface module for linking RS485 two-wire twisted shielded pair into RS232 port of PC.

(73)

HELP

This HeatChek control and monitoring unit is intended to be used with only the support of this instruction booklet. If special support needs do arise, Thermon provides local support through its area representatives and affi liate companies as well as through a toll free user support line.

For toll free support dial 1-800-820-HEAT(4328). Information may also be obtained by accessing 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

PROGRAM CIRCUIT NEW VALUE ENTER RESET LOW TEMP SEEN PROG

HIGH CURRENT ALARM

HIGH

CURRENT

PROGRAM

CIRCUIT

NEW

VALUE

LOW CURRENT ALARM

ATTACHMENT A: TC 1818A COMMAND FLOWCHART

(75)

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 ALARM

GROUND

CURRENT ENTER ENTER

PROGRAM CIRCUIT NEW VALUE PROG

DATA HIGHWAY

DATA

HWY ENTER ENTER

PROGRAM CIRCUIT NEW VALUE CIRCUIT # REPORTED FAULT CIRCUIT #

REPORTED FAULT ACK ALARM

ACK

ALARM ACKNOWLEGE

ALARM

ACK REPORTED FAULT HAS_{BEEN ACKNOWLEDGED} PROG

HEATER ENABLE/DISABLE

HEATER ENABLE ENTER PROGRAM CIRCUIT FORCE HEATER ON CIRCUIT # ENABLE (PIPE SENSE)

YES YES NO NO CIRCUIT FORCED ON CIRCUIT ENABLED/DISABLED CHANGE? CIRCUIT #

ENABLE (AMBIENT SENSE)

CIRCUIT # DISABLE

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