Pentair 920 Series Assembly instructions
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INDUSTRIAL HEAT TRACING SOLUTIONS
920 Series Heat Trace Controller
InstallatIon, operatIng and MaIntenance InstructIons
A/B
ALARM
LOCK
MONITOR CONFIG STATUS
ALARM
OUTPUT
SHIFT
ENTER
BACK
Raychem
920 SERIES
PROGRAMMABLE DUAL POINT
HEAT TRACING CONTROLLER
Tx
Rx
A
B
A/B
ALARM MONITOR CONFIG STATUS
ALARM
OUTPUT
SHIFT
BACK ENTER
Raychem
920 SERIES
LOCK
Firmware versions # up to V3.2X
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INDUSTRIAL HEAT TRACING SOLUTIONS
CONTENTS
Introduction .....................................................................................................................................................4
Certification..........................................................................................................................................4
Limited Warranty..................................................................................................................................4
Warranty Exclusion/Disclaimer ...........................................................................................................4
Exclusive Remedies .............................................................................................................................4
Conducted and Radiated Emissions—FCC/DOC Statement of Compliance .......................................4
What’s New ......................................................................................................................................................5
New Controller Features...................................................................................................................... 5
New Operator Console Features.......................................................................................................... 5
Section I – Overview.........................................................................................................................................6
1.1 Controllers Covered by this Manual..............................................................................................6
1.2 Product Overview...........................................................................................................................6
1.3 Modular Components....................................................................................................................8
1.4 Controller Assemblies...................................................................................................................9
1.5 Ordering and Configuration Guide ................................................................................................9
Section 2 – Installation and Wiring................................................................................................................11
2.1 Introduction ................................................................................................................................. 11
2.2 Initial Inspection .......................................................................................................................... 11
2.3 Operator Safety Considerations .................................................................................................. 11
2.4 Operating Environment ............................................................................................................... 11
2.5 Installation Location.................................................................................................................... 11
2.6 Mounting Procedures .................................................................................................................. 11
2.7 Wiring........................................................................................................................................... 13
2.8 Initial Power-up........................................................................................................................... 16
2.9 Setup for the 920 ......................................................................................................................... 17
Section 3 – Programming and Configuration.................................................................................................18
3.1 Introduction ................................................................................................................................. 18
3.2 Front Panel Features................................................................................................................... 18
3.3 920 Operator Console Display..................................................................................................... 19
3.4 920 Functions .............................................................................................................................. 19
3.5 Control Point Setup ..................................................................................................................... 19
3.6 Common Controller Setup .......................................................................................................... 28
3.7 Temperature Alarms ................................................................................................................... 30
3.8 Other Alarms ............................................................................................................................... 33
3.9 Communications Setup ............................................................................................................... 40
3.10 Operator Console Functions...................................................................................................... 43
3.11 Copy Configuration Functions (V3.11 and up) ........................................................................... 44
Section 4 – Monitored Parameters ................................................................................................................46
4.1 Introduction ................................................................................................................................. 46
4.2 Analog Readings.......................................................................................................................... 46
4.3 Maintenance Data........................................................................................................................ 47
Section 5 – Control Modes .............................................................................................................................49
5.1 Introduction ................................................................................................................................. 49
5.2 Switch Control Modes.................................................................................................................. 49
5.3 Load Shedding Control Mode ...................................................................................................... 51
5.4 TEMPBUS™ Control Mode .......................................................................................................... 52
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INDUSTRIAL HEAT TRACING SOLUTIONS
Section 6 – Troubleshooting ..........................................................................................................................53
6.1 Operator Checks ......................................................................................................................... 53
6.2 Common Problem Areas ............................................................................................................. 53
6.3 Common Alarms—What to look for ............................................................................................ 56
6.3 Common Alarms—What to look for(Continued) ......................................................................... 57
6.3 Common Alarms—What to look for(Continued) ......................................................................... 58
Section 7 – Maintenance................................................................................................................................59
7.1 Operator Maintenance................................................................................................................. 59
7.2 Replaceable Parts ....................................................................................................................... 59
Appendix A Specifications..............................................................................................................................60
Appendix B Typical Enclosure Dimensions...................................................................................................62
B.1 Single-Point Assemblies #10160-003 and #10160-009............................................................. 62
B.2 Dual-Point Assemblies #10160-120 and #10160-121 ................................................................ 63
B.3 Four-Point Assembly #10160-125............................................................................................... 64
B.4 Eight-Point Assembly #10160-035 .............................................................................................. 65
B.5 Twenty-Point Assembly #10160-045 ........................................................................................... 66
Appendix C Wiring Diagrams.........................................................................................................................67
C.1 TS Wiring..................................................................................................................................... 67
C.1.2 100Ω NICKEL IRON RTD WIRING.............................................................................................. 68
C.2 Power Wiring................................................................................................................................ 69
C.3 Communication Wiring C.3 Communication Wiring.................................................................... 70
C.4 Alarm Output Wiring .................................................................................................................... 70
C.5 External Input/Output Port Wiring............................................................................................... 72
Appendix D HTC Load Shedding Sequence ....................................................................................................73
Appendix E 100 Ω Platinum RTD Table ..........................................................................................................74
Appendix F 100 Ω Nickel-Iron RTD Table.......................................................................................................75
Appendix G Factory Default/Configuration Sheets ........................................................................................76
G.1 Configuration Sheet V3.00 ........................................................................................................... 76
G.2 920 Series HTC Configuration Sheet V3.1X and V3.2X................................................................. 79
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INDUSTRIAL HEAT TRACING SOLUTIONS
INTRODUCTION
Installation and Maintenance Instructions for Firmware Versions up to and Including V3.2X
This manual provides information pertaining to the installation, operation, testing, adjustment,
and maintenance of the Raychem Model 920 Series Heat Trace Control and Monitoring products.
Additional copies of the operating manual may be ordered separately through your Pentair
Thermal Managament representative or online at www.thermal.pentair.com using the document
number H56874.
Notice: The information contained in this document is subject to change without notice.
CERTIFICATION
Pentair Thermal Managament certifies that this product met its published specifications at the
time of shipment from the Factory.
LIMITED WARRANTY
This Pentair Thermal Managament product is warranted against defects in material and
workmanship for a period of 18 months from the date of installation or 24 months from the date of
purchase, whichever occurs first. During the warranty period, Pentair Thermal Managament will,
at its option, either repair or replace products that prove to be defective.
For warranty service or repair, this product must be returned to a service facility designated by
Pentair Thermal Managament. The Buyer shall prepay shipping charges to Pentair Thermal
Managament and Pentair Thermal Managament shall pay shipping charges to return the product
to the Buyer. However, the Buyer shall pay all shipping charges, duties, and taxes for products
returned to Pentair Thermal Managament from another country.
Pentair Thermal Managament warrants that the software and firmware designated by Pentair
Thermal Managament for use with the Raychem 920 Controller will execute its programming
instructions properly. Pentair Thermal Managament does not warrant that the operation of the
hardware, or software, or firmware will be uninterrupted or error-free
WARRANTY EXCLUSION/DISCLAIMER
The foregoing warranty shall not apply to defects resulting from improper or inadequate
maintenance by the Buyer, Buyer-supplied software or interfacing, unauthorized modification or
misuse, operation outside of the specifications for the product, or improper installation.
No other warranty is expressed or implied. Pentair Thermal Managament disclaims the implied
warranties of merchantability and fitness for a particular purpose.
EXCLUSIVE REMEDIES
The remedies provided herein are the buyer’s sole and exclusive remedies. Pentair Industrial Heat
Tracing Solutions shall not be liable for any direct, indirect, special, incidental, or consequential
damages, whether based on contract, tort, or any other legal theory.
CONDUCTED AND RADIATED EMISSIONSFCC/DOC STATEMENT OF COMPLIANCE
This equipment has been tested and found to comply with the limits for a Class A digital device,
pursuant to Part 15 of the FCC rules. These limits are designed to provide reasonable protection
against harmful interference when the equipment is operated in a commercial envi-ronment.
This equipment generates, uses, and can radiate radio frequency energy and, if not installed
and used in accordance with the instruction manual, may cause harmful interference to radio
communications. Operation of this equipment in a residential area is likely to cause harmful
interference, in which case the user will be required to correct the interference at his own
expense.
This equipment does not exceed Class A limits for radio emissions as set out in Schedule V to VIII
of the Radio Interference Regulations of Communication Canada.
Cet apparel respecte les limites de bruits radioelectriques applicables aux appareils numeriques
de Classe A prescrites dans la norme sur le materiel brouilleur: “Appareils Numeriques,” NMB-
003 edictee par le Ministre des Communications.
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INDUSTRIAL HEAT TRACING SOLUTIONS
WHAT’S NEW
This section provides a summary of the new features that have been added since the last version
of this manual was printed. It is assumed that the reader is already familiar with the earlier
versions of the 920 Controller.
NEW CONTROLLER FEATURES
• Alarmfilteringisnowavailablefor:
– LOW and HIGH TS ALARMS (see sections 3.7.7 on page 33 and 3.7.8 on page 34)
– LOW and HIGH CURRENT ALARMS (see sections 3.8.2 on page 35 and 3.8.4 on page 36)
– HIGH GFI ALARMS (see section 3.8.6 on page 36)
– LOW and HIGH VOLTAGE ALARMS (see sections 3.8.9 on page 37 and 3.8.11 on page 38)
– LOW and HIGH RESISTANCE ALARMS (see sections 3.8.13 on page 38 and 3.8.15 on page 39).
Alarm filtering will prevent an alarm from being indicated until the alarm condition has existed for
the duration of the alarm filter time.
• TwonewSWITCHCONTROLMODEShavebeenaddedforusewithAmbientTemperaturecontrol:
– Proportional Ambient SSR
– Proportional Ambient Contactor (see sections 3.5.3 on page 21 and 5.2 on page 50).
• ASCIIandRTUModBus™communicationsprotocolsupport(seesection3.9.1onpage42).
• Supportforanisolated,2-wireRS-485communicationsinterface(seesection1.4.5).
• A3-phasepowercalculationfeaturehasbeenincludedforusewithbalanced,Y-connected
heating loads (see section 3.5.10 on page 23).
• ATemperatureSensor(TS)FailModefeatureisnowavailabletoallowtheoutputtobeforced
ON or OFF when a control temperature failure occurs (see section 3.5.11 on page 23).
• ATEMPBUS™featuretoallowone“master”920controllertoshareitstemperaturesensor
information with up to 25 “slave” controllers (up to 50 control points). This includes the addition
of three TS CONTROL MODES (see sections 3.5.12 on page 24 and 5.4 on page 53).
• Supportfor100ohmnickel-ironRTDsalongwiththestandard100ohmplatinumtypes(see
sections 3.5.13 on page 24 and 3.5.16 on page 25).
• Manualvoltagesourceselection(seesection3.5.19onpage26).
• SupportforFORCEONandFORCEOFFmodesusingtheEXTERNALinput(seesections3.5.27
on page 28 and 3.6.3 on page 29).
• Featurestoreloadfactorydefaultparametersaswellascopyconfigurationparametersfrom
one point to another are now included (see section 3.11 on page 46).
• Newmaintenancealarmingtotrackcontactorwear(seesection3.8.23onpage42).
• MonitorPEAKLOADCURRENT,PEAKGFI,andtheEXTERNALINPUTSTATUSthrough
communications (see sections 4.3.6 on page 50, 4.3.7 on page 50, and 4.3.8 on page 50).
NEW OPERATOR CONSOLE FEATURES
• Theabilitytoadjustthedisplayscrollrateisnowavailable(seesection3.6.10onpage31).
• Maintenancedataresettingisnowsupported(seesection4.3onpage49).
• DisplayandresettheCONTACTORCYCLECOUNTER(seesection4.3.3onpage49).
• LimittherangeoftheCONTROLSETPOINTsettingfor920OperatorConsoleusers
(see sections 3.5.29 on page 29 and 3.5.30 on page 29).
• AnUNLOCKDATABASEfeaturewasaddedtothe920OperatorConsole’s“ConfigurationMode
Main Menu” (see section 3.10.3 on page 46).
• Thedisplaytestnolongeroccursatstartup;instead,theusermayactivateitfromamenu
option (see section 3.10.5 on page 46).
IMPORTANT WARNINGS AND NOTES
The following icons are used extensively throughout this manual to alert you to important
warnings that affect safety and to important notes that affect the proper operation of the
unit.
Be sure to read and follow them carefully.
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INDUSTRIAL HEAT TRACING SOLUTIONS
SECTION I OVERVIEW
1.1 CONTROLLERS COVERED BY THIS MANUAL
This document covers the 920 Series of heat trace controllers and available options. The
information coincides with the specific releases of firmware for the 920 product which are listed
on the cover. As Pentair Thermal Managament releases new firmware to modify or enhance
the product significantly, new documentation will accompany these releases. To ensure that
you are using the correct documentation for your particular version of controller, please check
the firmware version number of the 920 against the version number listed on the front of this
manual. This can be displayed using the optional 920 Operator Console or a communicating
device. As subsequent changes are made, supplements to this document will be included in
manuals shipped after the firmware is released. Supplements will make specific reference to the
operational or functional changes.
1.2 PRODUCT OVERVIEW
1.2.1 DESCRIPTION
The 920 Series Heat-Tracing Controller controls, monitors, and communicates alarms and data
for one or two heating circuits. As a dual-point device, it offers a complete range of control and
monitoring features, as well as superior reliability compared to multipoint systems. Its modular,
scalable architecture yields cost-effective multipoint assemblies without the expense of additional
control points that are not required. Available for use with external solid-state relays (SSRs) or
contactors in either one-, two-, or three-pole configurations and the ability to switch loads up to
600 Vac makes the 920 the most versatile product on the market.
1.2.2 FEATURES
A detailed description of available features can be found in Section III of this manual. Highlights of
specific features are included in the following text.
Front Display
The control module includes LED status indicators to show output and alarm conditions. Using
the optional 920 Operator Console, the setpoint temperature, actual control temperature, and load
current are immediately accessible to plant operators and maintenance staff. The display units are
field selectable for °F or °C.
–40°F to 140°F (–40°C to 60°C) Operation
Extended temperature operation permits installation in all but the harshest environments. SSR
output modules are limited to operating ambient temperatures of 104°F (40°C) without derating.
Single or Dual Temperature Sensor Inputs
The ability to use one or two temperature sensor (TS) inputs for each control point allows the
selection of one of eleven control modes and programming of all temperature parameters.
High and Low Temperature Alarms
High and low temperature alarms are offered for both inputs of each control point.
High and Low Current Alarms
Low current alarm is more than just a continuity level alarm. The 920 offers full adjustment over
the entire current measurement range for both high and low current alarm limits.
Solid State or Contactor Output
The 920 is available with externally-mounted solid-state relay (SSR) output switches or contactors.
With the SSR option, the user may select a time-proportional control algorithm, a simple
deadband mode, or one of two ambient control algorithms. The contactor versions always use
either the deadband mode or the proportional ambient contactor mode. Switching device failure
alarms are supported for both types of output devices.
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INDUSTRIAL HEAT TRACING SOLUTIONS
Ground-Fault Alarm and Trip
Ground-fault (GF) current levels are monitored and displayed in milliamps. The availability of the
actual ground-fault level gives the user the choice of both alarm and trip levels suitable for the
particular installation. Using multiple SSRs or a multipole contactor allows all powered legs of
non-neutral circuits to be switched off under GF conditions.
Overcurrent Protection
A unique overcurrent protection algorithm greatly reduces the possibility of damage to the circuit
or the controller in the event of a temporary overload while allowing for initially high in-rush
currents (SSR options only).
Soft Starting
Given the circuit breaker size, the 920 will limit the energy let-through to help prevent nuisance
breaker trips due to cable in-rush. This feature makes the controller particularly attractive for use
with self-regulating cables (SSR options only).
Minimum/Maximum Temperature Tracking
The controller maintains the minimum and maximum temperature values seen by the controller
since the last reset of these values. This is helpful in determining causes of temperature alarms.
Latching/Non-Latching Temperature Alarms
User-selectable, non-latching temperature alarms allow the controller to automatically clear the
alarm when the condition no longer exists.
High and Low Voltage Alarms
Operating at voltages less than design can cause serious loss of heater output. The alarming of
preset voltage deviations ensures availability of sufficient wattage output.
Power Limiting
The 920 will control the maximum output wattage if the full load power exceeds the specified
maximum power setpoint. This feature eliminates the need for low voltage transformers in many
applications and can assist in standardization of heating cable types (SSR options only).
Autocycling
The controller will energize the circuit for 10 seconds at a programmable interval. Circuit alarms
will be generated at the time of autocycle instead of when the heat is required. This feature
eliminates the need for a preventive maintenance program as these tests are performed at regular
intervals by the controller.
Temperature Sensor Failure Alarm
Both open and shorted sensors are detected and alarmed by the controller.
Random Start
A startup delay between 0 and 9 seconds ensures that all units do not come on line at the same
time.
Full Digital Communications
An optional internal communications interface allows the communication of alarms and analog
data to a monitoring system. Industry-standard RS-232 or RS-485 serial communications are
available for applications requiring direct interfacing to other devices. The modem version
maintains compatibility with legacy products including the GCC-9000/780 Series (Group
Communications Controller). With the availability of the heat trace data at the user’s fingertips,
historical trending of temperatures, power consumption, or other parameters are available for
analysis and system optimization.
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INDUSTRIAL HEAT TRACING SOLUTIONS
CSA C/US and c-ETL-us Approved
The 920 series of controllers is approved for Class I, Division 2, Groups A,B,C,D and Zone 2
hazardous locations, making it ideal for direct installation in the field. This can save the significant
expense of wiring back to a central-ly-located electrical distribution center.
1.3 MODULAR COMPONENTS
The 920 series controller is made up of a number of building blocks, allowing the ultimate in
design flexibility. Each component’s primary function is described below.
1.3.1 CONTROL MODULE
The 920 control module forms the heart of a single- or dual-point heat trace control solution. Each
plug-in module provides all of the intel-ligence required to control and monitor two independent
heat trace circuits. It includes indicators for alarm and output status and a connector for use with
a 920 Operator Console. An internal connector is provided to plug into an optional communications
interface.
The control module packaging provides a rugged, vibration-proof design. Once it is plugged into a
terminal board, the module is fastened using the two captive screws included as part of the rear
cover. It is important that these two screws be securely fastened whenever the module is powered.
1.3.2 TERMINAL BOARD
The terminal board eases maintenance and troubleshooting by providing a termination point for all
of the low-voltage signals. The 920 control module may be installed or removed without disturbing
the field wiring. Temperature sensor, communications, and alarm control wiring are connected to
the lever-operated spring terminals, providing gas-tight, vibration-resistant connections.
1.3.3 OPERATOR CONSOLE
A large, easy-to-read alphanumeric display and menu-driven interface ease controller
configuration and eliminate the need for an external programmer. The console may be left
installed permanently or may be installed temporarily for display/setup during maintenance and
trou-bleshooting. Access is available for all monitored parameters, programmed values, and
alarm information. Enhanced security is provided by password protection.
The unique design of the operator console allows it to be installed or removed under power, even
in hazardous areas.
1.3.4 SWITCH INTERFACE
Universal single-phase current monitoring, single- or 3-phase ground-fault detection, and voltage
monitoring are provided by the Switch Interface (SIS/SIC) module. One device is required for each
control point, and two versions are available: SIS for use with SSRs, and SIC for use with the
contactor. Both units also incorporate a universal power supply, allowing operation directly from
100 Vac to 277 Vac. Use with higher trace voltages is also possible, using a separate power source
or a small step-down transformer.
Redundant operation is supported, allowing a control module to automatically power itself from
either of two switch interface modules or both. This permits one heat-trace circuit to be turned off
for maintenance without affecting the operation of the other circuit.
1.3.5 COMMUNICATIONS INTERFACE
In applications where the user wishes remote configuration capability or wants to communicate
trace information and/or alarms to another device such as the GCC (Group Communications
Controller), an optional communications interface may be installed in the control module.
A modem version that maintains compatibility with legacy products is available, or other industry-
standard interfaces such as RS-232 and RS-485 may be specified.
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INDUSTRIAL HEAT TRACING SOLUTIONS
1.3.6 SOLID-STATE RELAY OUTPUT MODULE
In applications where the benefits of solid-state control are desired, a modular solid-state relay
(SSR) is available. This component is easily installed on the outside of an enclosure using a single
3/4 NPT knockout and locknut providing a weatherproof seal. This allows the heat generated by
the SSR to be dissipated directly to the ambient air, without increasing the internal temperature of
the enclosure. When appli-cations require two-pole or 3-phase switching, multiple SSR modules
may be ganged together, allowing the same component to be used.
1.4 CONTROLLER ASSEMBLIES
Due to its modular packaging, the 920 easily supports single-, dual-, or multi-point configurations.
Factory standard assemblies are available in a variety of enclosure types, and panels made up
of multiple points are also available. Refer to the Ordering Guide in section 1.5 on page 10 for
a sample listing of available configurations. If your application requires a customized solution,
please contact your Pentair Thermal Managament representative for help in specifying an
assembly suited to your particular requirements.
1.5 ORDERING AND CONFIGURATION GUIDE
920 series control assemblies are ordered as three separate items:
Tx
Rx
A
B
A/B
ALARM
LOCK
MONITOR CONFIG STATUS
ALARM
OUTPUT
SHIFT
BACK ENTER
Raychem
920 SERIES
PROGRAMMABLE DUAL POINT
HEAT TRACING CONTROLLER
Enclosure assembly Control module(s)
(One for every two circuits)
Optional operator
console(s)
PROGRAMMABLEDUAL POINT
HEATTRACING CONTROLLER
A/B
ALARM
LOCK
MONITOR CONFIG STATUS
ALARM
OUTPUT
SHIFT
BACK ENTER
Raychem
920 SERIES
Fig. 1.6 920 series control assemblies
Pentair Thermal Managament maintains a shelf stock of enclosure assemblies, control modules,
and consoles. All other enclosure assemblies are built to order. Not all options may be listed.
Contact your local representative for any special applications you may have.
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INDUSTRIAL HEAT TRACING SOLUTIONS
1.5.1 ENCLOSURE ASSEMBLY
Enclosure Assemblies
Description Catalog number Part number Weight/lbs
Raychem 920 controller–2 Pt in a 14" x 12" x 8" FRP
enclosure with window and quick-release latches,
control module, and operator console. 1P 30 A 277 V
SSR/pt. Controls two circuits, each with a 1-pole
solid-state relay. (Approved for Class 1, Div. 2 areas)
920*E4FWL*SIS302*SS3102*HTC*CON 10160-010 27
Raychem 920 controller–2 Pt in a 14" x 12" x 8" FRP
enclosure with window and quick-release latches,
control module, and operator console. Includes an
isolated 2-wire RS-485 communication option. 1P
30 A 277 V SSR/pt. Controls two circuits, each with
a 1-pole solid-state relay. (Approved for Class 1, Div.
2 areas)
920*E4FWL*SIS302*SS3102*HTC485*CON 10160-011 27
Raychem 920 controller–2 Pt in a 14" x 12" x 8" FRP
enclosure with window and quick-release latches,
control module, and operator console. 2P 30 A 277 V
SSR/pt. Controls two circuits, each with a 2-pole
solid-state relay. (Approved for Class 1, Div. 2 areas)
920*E4FWL*SIS302*SS3202*HTC*CON
10160-012 32
Raychem 920 controller–2 Pt in a 14" x 12" x 8" FRP
enclosure with window and quick-release latches,
control module, and operator console. Includes an
isolated 2-wire RS-485 communication option. 2P
30 A 277 V SSR/pt. Controls two circuits, each with
a 2-pole solid-state relay. (Approved for Class 1, Div.
2, areas)
920*E4FWL*SIS302*SS3202*HTC485*CON 10160-013 32
Raychem–Raychem Supervisory Software Raychem Supervisor 10391-002 1
IMPORTANT: The NEC (and CEC) rules specify that all ungrounded—i.e., hot—legs of a circuit, must be switched in the event of a
ground fault. This means for 207 V single-phase applications, you must specify a 2-pole (2P) version if you are not using external GFI
breakers.
Control Modules
Raychem 920 controller–Control module only
(No communications options installed)
920HTC 10260-001 1
Raychem 920 controller–Control module
with an isolated
2-wire RS-485 communication option installed
920HTC*485 10260-004 1
Raychem 920 controller–Control module
with modem
communications option installed
920HTC*MDM 10260-002 1
Operator Console
Raychem 920 controller–Operator console 920CON 10260-005 1
Contact your local representative for other available configurations that are not
listed above.
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1.5.1 ENCLOSURE ASSEMBLY
Enclosure Assemblies
Description Catalog number Part number Weight/lbs
Raychem 920 controller–2 Pt in a 14" x 12" x 8" FRP
enclosure with window and quick-release latches,
control module, and operator console. 1P 30 A 277 V
SSR/pt. Controls two circuits, each with a 1-pole
solid-state relay. (Approved for Class 1, Div. 2 areas)
920*E4FWL*SIS302*SS3102*HTC*CON 10160-010 27
Raychem 920 controller–2 Pt in a 14" x 12" x 8" FRP
enclosure with window and quick-release latches,
control module, and operator console. Includes an
isolated 2-wire RS-485 communication option. 1P
30 A 277 V SSR/pt. Controls two circuits, each with
a 1-pole solid-state relay. (Approved for Class 1, Div.
2 areas)
920*E4FWL*SIS302*SS3102*HTC485*CON 10160-011 27
Raychem 920 controller–2 Pt in a 14" x 12" x 8" FRP
enclosure with window and quick-release latches,
control module, and operator console. 2P 30 A 277 V
SSR/pt. Controls two circuits, each with a 2-pole
solid-state relay. (Approved for Class 1, Div. 2 areas)
920*E4FWL*SIS302*SS3202*HTC*CON
10160-012 32
Raychem 920 controller–2 Pt in a 14" x 12" x 8" FRP
enclosure with window and quick-release latches,
control module, and operator console. Includes an
isolated 2-wire RS-485 communication option. 2P
30 A 277 V SSR/pt. Controls two circuits, each with
a 2-pole solid-state relay. (Approved for Class 1, Div.
2, areas)
920*E4FWL*SIS302*SS3202*HTC485*CON 10160-013 32
Raychem–Raychem Supervisory Software Raychem Supervisor 10391-002 1
IMPORTANT: The NEC (and CEC) rules specify that all ungrounded—i.e., hot—legs of a circuit, must be switched in the event of a
ground fault. This means for 207 V single-phase applications, you must specify a 2-pole (2P) version if you are not using external GFI
breakers.
Control Modules
Raychem 920 controller–Control module only
(No communications options installed)
920HTC 10260-001 1
Raychem 920 controller–Control module
with an isolated
2-wire RS-485 communication option installed
920HTC*485 10260-004 1
Raychem 920 controller–Control module
with modem
communications option installed
920HTC*MDM 10260-002 1
Operator Console
Raychem 920 controller–Operator console 920CON 10260-005 1
Contact your local representative for other available configurations that are not
listed above.
SECTION 2 INSTALLATION AND WIRING
CAUTION:
Be sure all personnel involved in installation, servicing, and programming are qualified and
familiar with electrical equipment, their ratings and proper practices and codes. Multiple voltages
and signal levels may be present during the installation, operation, and servicing of this product.
Do not power the product until the safety provisions outlined in this section have been observed.
2.1 INTRODUCTION
This section includes information on the initial inspection, preparation for use, and storage
instructions for the 920 series heat trace controller.
CAUTION:
Solid-state relay (SSR) modules may be extremely hot immediately after power is removed.
Exercise care when handling SSRs.
2.2 INITIAL INSPECTION
Inspect the shipping container for damage. If the shipping container or cushioning material is
damaged, it should be kept until the contents of the shipment have been verified for completeness
and the equipment has been checked mechanically and electrically. Procedures for configuring
and operating the heat trace controller are given in Section 3 on page 18. If the shipment is
incomplete there is mechanical damage, a defect, or the controller does not pass the electrical
performance tests, notify your Pentair Thermal Managament representative. If the shipping
container is damaged, or the cushioning material shows signs of stress, notify the carrier as
well as your Pentair Thermal Managament representative. Keep the shipping materials for the
carrier’s inspection.
2.3 OPERATOR SAFETY CONSIDERATIONS
The standard 920 controller using solid-state relays is suitable for Class I, Division 2, Groups A,
B, C, D and Zone 2 hazardous areas. Haz-ardous areas are defined by Article 500 of the National
Electrical Code and Section 18 of the Canadian Electrical Code. Contactor-based assemblies are
suitable for use in ordinary (non-hazardous) areas only.
CAUTION:
Many wiring configurations will use more than one power source and all must be de-energized
prior to performing any maintenance on a controller circuit.
2.4 OPERATING ENVIRONMENT
The operating environment should be within the limitations described in the 920 heat trace
controller specifications outlined in Appendix A on page 61.
2.5 INSTALLATION LOCATION
The wide ambient operating temperature range of the controller permits installation in any
convenient location. Considerations should include expected atmospheric conditions, accessibility
for maintenance and testing, the location of existing conduits, and hazardous area rating. Ambient
temperature conditions may affect load current ratings.
CAUTION:
Always be sure that the intended location is classified as an area that the product is approved for
as defined by Article 500 of the National Electrical Code and/or Part I, Section 18 of the Canadian
Electrical Code.
2.6 MOUNTING PROCEDURES
Mounting hole dimensions for the standard enclosures are shown in Appendix B on page 63. If
possible, conduit entries should be made in the bottom of the enclosure to reduce the possibility
of water entry or leakage. Conduit entries must be drilled/punched following the enclosure
manufacturer’s recommendations. Use bushings suitable for the enclosure type and install
such that the completed installation remains waterproof. Grounding hubs and conductors must
be installed in accordance with Article 501-4(b) of the National Electrical Code and Part I of the
Canadian Electrical Code.
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Theusermaywanttoconsiderenclosuredrainholesinapplicationswheremoistureisaproblem;
drill 0.125" holes in the bottom of the enclosure on both the left and right sides. Two holes reduce
the possibility that one will plug and ensures drainage if the enclosure is not perfectly level.
Note that drilling holes in the enclosure compromises the NEMA 4 rating. Controllers should be
removed from the enclosure before any holes are drilled or cut to prevent damage due to flying
debris.
2.6.1 CONTROL MODULE INSTALLATION AND REMOVAL
CAUTION:
Always ensure that the power to the unit is turned off during installation or removal to avoid the
risk of injury and damage to the controllers.
WARNING:
Explosion Hazard! Do not install or remove the control module while the unit is powered.
Fig 2.1 Control module installation
The 920 series controller is designed to be mounted to a flat back plate/panel using a terminal
board. This plug-in design simplifies installation and maintenance by allowing all of the low-
voltage field wiring to remain undisturbed while a control module is installed or removed.
Installation of the control module is easily accomplished by plugging it into the connector on the
terminal board.
• Themoduleisfullyinsertedonceitsrearcoverisflushtothetopsurfaceoftheterminalboard.
The connectors are designed to be self-aligning, so no undue force should be required.
• Next,securethemoduleusingthetwocaptivescrewsprovided(onelocatedoneachsideof
the rear cover). These should thread easily into the terminal board. Be sure to align the screws
properly to avoid cross-threading them.
To remove the control module, loosen the two captive screws. Once they have been completely
loosened, they will float freely in their re-spective retaining collars without falling out. The module
may now simply be pulled straight out of its connection.
2.6.2 OPERATOR CONSOLE INSTALLATION AND REMOVAL
The operator console is designed to be easily installed or removed while the controller is
powered—even in Class I Division 2 and Zone 2 hazardous areas. It may be temporarily or
permanently installed.
The console is installed in three steps:
Step “Hook” the lip provided on the rear cover of the console over the top edge of the control
module front plate.
Fig. 2.2 Console installation – Step 1
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Step “Hinge” the bottom of the console downwards until it is flush with the front of the control
module.
Fig. 2.3 Console installation – Step 2
Step If the console is to be permanently installed, secure it to the control module using the
captive screw provided. It should be finger tight only. Do not over-tighten the screw or damage to
the console housing may occur.
Fig. 2.4 Console installation – Step 3
To remove the console, follow the three steps outlined above in reverse order.
2.7 WIRING
Wiring diagrams for typical configurations are included in Appendix C on page 68.
CAUTION:
Always verify wiring connections before applying power to the controller or connected circuits. To
avoid injury or equipment damage, do not install or remove wiring while controller power is on.
To minimize the chance of loose connections, the terminal board uses lever-operated, spring-
loaded terminals. See Appendix A on page 61 for allowable wire sizes and recommended
insulation strip lengths.
2.7.1 TEMPERATURE SENSOR CONNECTIONS
Use shielded, twisted, three-conductor wire for the extension of RTD leads. The wire size should
ensure that the maximum allowable lead resistance is not exceeded. Shields on RTD wiring should
be grounded at the controller end only, using the terminals provided.
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Temperature Sensors Terminal No.
Point A – Shield 25
Point A TS 1 Source (WHT) 26
Point A TS 1 Sense (WHT) 27
Point A TS 1 Common (RED) 28
Point A – Shield 9
Point A TS 2 Source (WHT) 10
Point A TS 2 Sense (WHT) 11
Point A TS 2 Common (RED) 12
Point B – Shield 29
Point B TS 1 Source (WHT) 30
Point B TS 1 Sense (WHT) 31
Point B TS 1 Common (RED) 32
Point B – Shield 13
Point B TS 2 Source (WHT) 14
Point B TS 2 Sense (WHT) 15
Point B TS 2 Common (RED) 16
IMPORTANT: Some RTDs may be constructed with the Sense wire color-coded as Black.
2.7.2 ALARM RELAY CONNECTIONS
The alarm output relay is a programmable dry contact output. It may be programmed for N.O.,
N.C., steady or flashing operation, and is typically used to annunciate an alarm to an external
device such as a DCS, PLC, etc.
IMPORTANT: The alarm relay is intended to be used for switching low-voltage, low-current
signals.
Do not use this relay to directly switch line voltages.
Ensure that your application stays
within the ratings of the relay contacts as defined in Appendix A on page 61.
The alarm relay may also be used in conjunction with the +9 Vdc source to switch an external,
line-voltage relay to drive a local pilot light, etc. Refer to the wiring diagrams in Appendix C on
page 68 for example connection details.
Alarm and Control Signals Terminal No.
Alarm relay dry contact output 17
Alarm relay dry contact output 18
Ground 19
+9 Vdc nominal Out (100 mAmps maximum) 1
Common 2
Common 3
2.7.3 EXTERNAL INPUT/OUTPUT
These input and output terminals are used to implement the Override and Ambient Temperature
Control Mode features. Refer to Section 3 on page 18 for programming details, and Appendix C on
page 68 for example wiring diagrams.
Miscellaneous Signals Terminal No.
External input (+) 20
External input (-) 21
External output (+) 4
External output(-) 5
2.7.4 COMMUNICATION SIGNAL CONNECTIONS
The communications terminal assignments change based on the type of option installed. If present
in a control module, the type of communications interface will be identified by a label located next
to the module’s rating label.
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Communications wiring should use twisted conductor, shielded cable. Shields on communications
wiring should be grounded at one end only, using the terminals provided.
The following tables define the appropriate signal connections for the various types of interfaces:
RS-485 (2-Wire) Connections
Communication Signal Terminal No.
Receive/transmit data (+) 6
Receive/transmit data (-) 22
Shield 8
Shield 24
RS-232 Connections
Communication Signal Terminal No.
Receive data 6
Data carrier detect 7
Clear to send 8
Transmit data 22
Request to send 23
Common 24
Modem Interface Connections
(Note that these particular signals are not polarity sensitive)
Communication Signal Terminal No.
Modem 6
Modem 22
Shield 8
Shield 24
2.7.5 POWER CONNECTIONS
All of the power terminals are numbered for easy identification. Do not attempt to use wire sizes
that exceed the marked terminal ratings and avoid terminating two wires on the same terminal
whenever possible.
Always be sure that all terminals are adequately tightened according to the terminal anufacturer’s
specification. See Appendix A on page 61 for allowable wire sizes, recommended insulation strip
lengths, and tightening torque. A loose terminal can cause arcing and damage to the terminal or
incorrect operation of the controller.
IMPORTANT: Make sure that power terminals are re-tightened several days after installation.
Strandedwirewilltendtocompresswheninitiallyinstalled;therefore,theseterminalsshouldbe
checked for tightness several times after the system is installed to ensure that a good con-nection
is maintained. Be certain to use the proper size screwdriver for the terminal blocks to minimize
the chance of damage to the termi-nals.
If the controllers are installed in either a metallic or non-metallic enclosure, follow the enclosure
manufacturer’s recommendations for proper grounding. Do not rely on conduit connections to
provide a suitable ground.
Grounding terminals/screws are provided for connection of system ground leads. Proper system
grounding is required for safe and correct operation of the controller’s protection features.
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2.7.6 INPUT POWER
The 920 controller may be powered directly from the trace voltage (120 Vac to 277 Vac), through a
step-down transformer, or from a sepa-rate circuit. The same wiring terminal assignments are
used in all configurations, as defined below:
Power Connections Terminal No.
Line/L1 power input 1
Line/L1 Control Power Input 2
Neutral/L2 Power Input 3
Neutral/L2 Control Power Input 4
L3 Power Input (3Ph only) 5
Line/L1 Output to Trace 6
Neutral/L2 Output to Trace 7
L3 Output to Trace (3Ph only) 8
IMPORTANT: that terminals 5 and 8 are only used for implementing 3-phase switching (this is true
for both SSR and contactor configurations).
When powering the controller directly from the incoming trace power (120 Vac to 277 Vac), jumpers
are installed between terminals 1 and 2 and 3 and 4. This is the standard factory configuration.
When the controller is to be powered from another voltage source, the jumpers between terminals
1 and 2 and 3 and 4 should be removed, and the controller power connected to terminals 2 and 4.
In applications where a neutral-based 4-wire 3-phase source is available, the controller may be
powered from one line to neutral connec-tion, while the trace is operated from the line-to-line
connection, eliminating the need for step-down transformers or separate power sources. This can
be accomplished by removing the jumper between terminals 3 and 4 only. Controller power can
then be derived from the L1 trace power on terminals 1 and 2 and the incoming neutral connection
for controller power would be connected to terminal 4.
Wiring diagrams for typical 1- and 2-pole configurations are included in Appendix C on page 68.
IMPORTANT: The contactor version Switch Interface modules provide a switched line voltage
signal to drive the contactor coil. This is derived from the control power and, as such, requires that
the contactor coil voltage be specified to match the control voltage present on terminals 2 and 4.
CAUTION:
Many wiring configurations will use more than one power source and all must be de-energized
prior to performing any maintenance on a controller circuit. When servicing one control point,
remember that power may also be present on the second control point.
2.8 INITIAL POWERUP
CAUTION:
Before applying power to the controller, ensure that powering the circuit will not damage it if power
limiting or the setpoint temperature have not been set correctly. If there is any doubt, the load
should be disconnected until the 920 has been suitably programmed for correct and safe operation.
2.8.1 INITIAL CABLE TEST
To minimize the risk of damage to the controller due to a cable fault, the integrity of the heating
cable should be verified by:
1. Using a megger to perform a high-voltage insulation test
2. Using an ohmmeter to ensure that the heating cable is not shorted
These tests must be performed with the controller output disconnected.
Once the cable has been
checked, it may be reconnected to the controller and power applied.
2.8.2 RANDOM START DELAY
All920seriescontrolmodulesincorporateaRANDOMSTART-UPDELAYfeature,ensuringthat
all units do not power on at the same time. When power is first applied to a controller, it will
hold its output off for a random time (0 to 9 seconds), equal to the last digit of the HTCBUS™
communications address (see section 3.9.2 on page 43). Once the start-up delay has timed out, the
controller will begin normal operation.
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2.9 SETUP FOR THE 920
The 920 may be programmed using the optional 920 Operator Console, or a Group
Communications Controller (GCC) if the modem commu-nications option is installed. For
instructions on the operation of these devices, refer to the corresponding operating manuals.
For complete instructions on programming the 920, see the Section 3 on page 18.
2.9.1 VOLTAGE READING SETUP
The 920 series control module is tested, calibrated, and ordered separately from the switch
interface modules which contain the voltage sensing circuitry. This prevents Pentair Industrial
Heat Tracing Solutions from calibrating the control modules to specific switch interfaces and
removing any component inaccuracies. Generally, the voltage readings will be within 3 Vac to 5 Vac
when shipped from Pentair Thermal Managament. If more accurate voltage readings are desired,
they may be adjusted as part of the initial setup of the controller. This requires measurement of
the trace voltage using a multimeter and adjusting the VOLTAGE TURNS RATIO setting to arrive at
more accurate voltage readings. See section 3.5.21 on page 26.
2.9.2 SWITCH RATING SETUP (SSR ONLY)
The 920 series control module is ordered and shipped as a separate item from the enclosure
assembly. This prevents Pentair Thermal Managament from predetermining the SWITCH
CURRENT RATING settings since various types of output switches are available.
The user should verify that the switch current ratings are set properly for the rating of the solid-
state relays that are included as part of the enclosure assembly.
Refer to section 3.5.7 on page 22
for more information on the SWITCH CURRENT RATING setting. Pentair Thermal Managament
default setting is defined in Appendix F on page 76.
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SECTION 3 PROGRAMMING AND CONFIGURATION
3.1 INTRODUCTION
This section provides complete operating and setup instructions for the 920 Series Heat-Tracing
Controller. The text describes each available function in detail, its purpose, valid range settings,
the procedure for use, and some operational tips and suggestions.
While configuring the controller, it is important to remember that the 920 series controller is a
two control point device. Both control points allow completely independent operation and, as such,
have their own individual settings that must be configured. Throughout the text, the first control
point is referred to “Point A” and the second as “Point B.”
PROGRAMMABLE DUAL POINT
HEAT TRACING CONTROLLER
CONSOLE INTERFACE
920 SERIES
POWER
TRANSMIT
RECEIVE
ADDRESS
ALARM
“Power On” LED
Communications status
indicators
Alarm status
indicators
AB
OUTPUT
A - 20910
B - 20911
Output status
indicators
Operator
console
connection
Communications addresses
for Control Point A and
Control Point B
Fig 3.1 Raychem 920 front panel
3.2 FRONT PANEL FEATURES
Front panel features of the heat trace controller are shown in Figure 3.1. The remainder of this
Section describes the front panel status and display LEDs.
3.2.1 920 FRONT PANEL DISPLAY
The basic 920 series control module front panel includes seven LED indicators. Four of these are
used to indicate the “Output” and “Alarm” status of control points A and B.
Status LEDs
OUTPUT The OUTPUT LED, when illuminated steadily, indicates that the output of the controller
is turned on and is allowing current to flow in the trace circuit. For SSR versions, a flashing LED
indicates that the controller is pulsing its output on and off to maintain the setpoint temperature
and/or control the average amount of current/power the tracer uses. A separate LED is provided
for Point A and Point B.
ALARM The ALARM LEDs will flash (approximately once per second) when the controller has
detected an alarm condition. A separate LED is provided for Point A and Point B.
TRANSMIT The TRANSMIT LED (“Tx”) flashes when the controller is sending information over its
communications port to another device. This LED is only used when an optional communications
interface is installed.
RECEIVE The “RECEIVE” LED (“Rx”) flashes when the controller is receiving information
over its communications port from another device. This LED is only used when an optional
communications interface is installed.
POWER Indicates the module is powered on.
IMPORTANT: Older versions of the controller may not have this LED.
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3.3 920 OPERATOR CONSOLE DISPLAY
The optional 920 Operator Console provides a menu-driven, alphanumeric interface to
ease configuration and troubleshooting. The following features are part of the controller’s
programming, but are only used in conjunction with the 920 Operator Console. For a detailed
description of each of the console features and operating instructions, refer to the separate
Raychem 920 Series HTC Operator Console—Installation and Operating Instructions
(Pentair
Thermal Managament reference H56903).
3.4 920 FUNCTIONS
The sections that follow explain the various functions of the 920 controller and how they can be
accessed. The first line of each section identifies the function to be described. Each section goes
on to explain the Purpose of the function, the Range over which it may be set, the Procedure for
setting or enabling the feature, and finally any Notes or Cautions that pertain to the particular
function.
Setting and using the alarming functions of the 920 controller is a two step procedure:
1. The alarm must be enabled or disabled accordingly. When using the 920 Operator Console,
access to all alarming functions is available using the CONFIGURE mode sub-menus. When
using the Model 780/GCC-9000 Group Communications Controller, the alarm masks may be
found in the HTC SETUP Section. Please see the appropriate operating manual for instructions
on accessing these parameters.
2. The corresponding alarm point value may be modified appropriately for the application.
When using the 920 Operator Console, access to the alarm points is also available using the
CONFIGURE mode sub-menus. Modification of the alarm setpoint values is found in the HTC
SETPOINTS Section of the Model 780/GCC-9000 Group Communications Controller. Please see
the appropriate operating manual for in-structions on accessing this feature.
IMPORTANT: The 920 Operator Console or the Model 780/GCC-9000 will
not
allow modification
of an alarm point value if the alarm has been disabled (DIS) with the exception of the HIGH TS
ALARM temperature settings. These may still be modified if the corresponding HIGH LIMIT
CUTOUT has been enabled (ENA).
3.5 CONTROL POINT SETUP
This Section describes the setup parameters that relate to a specific control point—either Point A
or Point B. These parameters must be configured for each of the two control points that are used.
3.5.1 CONTROL SETPOINT TEMPERATURE
Purpose: The CONTROL SETPOINT temperature is the value at which the heat trace controller
maintains the circuit temperature through either proportional, proportional ambient SSR,
proportional ambient contactor, or deadband control, depending on the controllers’ configuration.
The CONTROL SETPOINT temperature is compared to the temperature measured by the control
temperature sensor (TS). A decision is then made to turn on or turn off the output to control power
to the tracer.
Range: –76°F to 1058°F (–60°C to 570°C)
Procedure: Adjust the CONTROL SETPOINT temperature value to the desired maintain
temperature. The HTC will switch the output ON and OFF in an attempt to maintain this
temperature.
IMPORTANT:
• Seesection5.2onpage50ofthismanualforanexplanationofProportional,Proportional
Ambient SSR, Proportional Ambient Contactor and Deadband Control algorithms.
• Whenusinganoptional920OperatorConsole(forV3.11andup)theCONTROLSETPOINT
temperature range may be limited to the CON-SOLE SETPOINT MAXIMUM and MINIMUM
values (see sections 3.5.29 on page 29 and 3.5.30 on page 29). This is a safety feature to pre-
vent users in the field from modifying the CONTROL SETPOINT temperature setting to a
dangerous level.
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3.5.2 ALPHANUMERIC TAG ASSIGNMENT
Purpose: A 19-character alphanumeric TAG may be assigned to a control point to allow it to be
easily associated with a pipe, vessel, process, circuit, drawing name or number.
Setting: Any combination of 19 characters from A-Z, 0-9, /, -, ., (,) or #.
Procedure: Using the 920 Operator Console, enter the desired text. Refer to the separate
Raychem 920 Series HTC Operator Console—Installation and Operating Instructions
(Pentair
Thermal Managament reference H56903) for TAG entry information.
3.5.3 SWITCH CONTROL MODE
Purpose: This allows selection of the type of algorithm to be used by the HTC to maintain the
CONTROL SETPOINT temperature. There are four different control algorithms available in the HTC—
proportional, proportional ambient SSR, proportional ambient contactor, and deadband. See section
5.2 on page 50 for a complete explanation of these controlling techniques as implemented in the HTC.
Setting: PROPORTIONAL, PROPORTIONAL AMBIENT SSR (V3.11+), PROPORTIONAL AMBIENT
CONTACTOR (V3.11+), or DEADBAND
Procedure: Select the desired control technique. Note that deadband control and proportional
ambient contactor should be selected when using contactors or when precise control and
advanced current handling functions are not required.
IMPORTANT: If deadband is selected, a DEADBAND setting will be available in the HTC
configuration menu, else a PROPORTIONAL BAND setting will be available. No MAXIMUM POWER,
SWITCH CURRENT RATING or CIRCUIT BREAKER CURRENT RATING settings are available when
the controller is set to operate in either contactor mode. If proportional ambient contactor is
selected,theCYCLETIMEsettingwillalsobeavailable.
3.5.4 PROPORTIONAL BAND SETTING
(For use with the three proportional control modes only)
Purpose: When an HTC equipped with SSRs is used to control a heating circuit, proportional or
proportional ambient SSR modes are normally used, allowing for more precise temperature control.
When using contactors, the proportional ambient contactor mode should be selected.
This programmable proportional band acts to vary the on to off time of the output based on the
difference between the measured control temperature and the desired CONTROL SETPOINT
temperature.
Range: 2°F to 90°F (1°C to 50°C)
2°F to 630°F (1°C to 350°C) V3.2x and up
Procedure: Adjust the PROPORTIONAL BAND setting to the desired differential from the
CONTROL SETPOINT temperature.
IMPORTANT:
• Seesection5.2onpage50foranexplanationofhowthethreeproportionalmodesusethe
PROPORTIONAL BAND setting.
• Whenusingseries-type,constantwattage,orself-regulatingtracersinanambient
temperature control application, significant energy savings may be realized by setting the
PROPORTIONAL BAND to match the expected range of operating ambient temperatures.
Tracer design is normally done assuming worst-case conditions, where 100% of the design
output power is required to maintain the desired minimum temperature. When the ambient
temperature is above the design minimum but some heat is still required, adjusting the
PROPORTIONAL BAND width accordingly will allow only the amount of power required by the
application to be consumed, while maintaining the minimum required temperature.
Example: A water line must be protected from freezing when the ambient temperature falls below
10°C. Either the proportional ambient SSR or proportional ambient contactor mode is selected
as the control method (depending on the type of switch being used). The heater and insulation
are chosen to impart enough heat to the line to keep it from freezing at a worst-case ambient
temperature of –40°C. At 10°C, the heater should be completely off, since no heat is required at
this temperature to guarantee that the product will not freeze. It follows that the amount of heat
required by the water line decreases as the ambient temperature increases from –40°C to 10°C
(theoretically, at –15°C the heater output should be approximately 50%). Setting the CONTROL
SETPOINT temperature to 10°C, and the PROPORTIONAL BAND to 50°C, will force the controller’s
output to be 100% on at –40°C, 50% on at –15°C, and off at 10°C.
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