DigiTrace 920 Series Heat Trace Controller - Pentair Thermal ...

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• Verify that the RTD is wired correctly. The heat-tracing controllers will always be terminated inthe order: source (WHT), sense (WHT), common (RED). When using the terminal board, theseterminals are marked as follows:Terminal No.description25 Point A, Shield26 Point A, TS 1 Source (WHT)27 Point A, TS 1 Sense (WHT)28 Point A, TS 1 Common (RED)9 Point A, Shield10 Point A, TS 2 Source (WHT)11 Point A, TS 2 Sense (WHT)12 Point A, TS 2 Common (RED)29 Point B, Shield30 Point B, TS 1 Source (WHT)31 Point B, TS 1 Sense (WHT)32 Point B, TS 1 Common (RED)13 Point B, Shield14 Point B, TS 2 Source (WHT)15 Point B, TS 2 Sense (WHT)16 Point B, TS 2 Common (RED)The RTD manufacturer will typically color code the leads with the source and sense being thesame color, and the common a different color. Ensure that the RTD extension wire shield isterminated at one end only, normally using the terminal block provided at the terminal board.IMPORTANT: Some RTDs may have the Sense wire color coded as Black.2. Questionable TemperatureIf you feel that the indicated or displayed temperature is not correct, the controller and the RTDcan be quickly checked for correct operation.To verify the RTD:Turn off the power to the controller before proceeding!• Disconnect the RTD wiring from the input terminals.• To calculate the temperature indicated by the RTD, measure the resistance from source(white wire) or sense (white wire) to common (red wire) and subtract the resistance measuredbetween source and sense. This will give a compensated resistance value that can be crossreferencedto the RTD table, DIN Standard 43760 found in Appendix D on page 74 or AppendixE on page 75. Compare the meas-ured resistance and cross-referenced temperature valueobtained from the RTD table to the indicated or displayed value. These should agree to withinthe accuracy standards of the HTC and the RTD.To verify the Controller:Turn off the power to the controller before proceeding!• Disconnect the RTD wiring from the input terminals.• Connect a 100 Ω resistor across the source or sense terminal and common. Insert a jumperbetween the source and sense terminals.• Apply power to the controller. The indicated or displayed temperature should be about 0°C(32°F) depending on the actual resistance of the test resistor if TS TYPE is set to 100 ΩPlatinum.3. Unstable or Bouncing TemperatureAn erratic indication of temperature can be caused by several factors external to the controller;however, a bouncing temperature of a few degrees should not be confused with incorrectoperation. The controller’s accuracy and resolution will result in an indicated temperaturechange of a couple of degrees if the measured resistance temperature falls between twodiscrete values. This is sometimes referred to as quantization error.THERMAL MANAGEMENT SOLUTIONS EN-DigiTrace920series-IM-H56874 04/13 54 / 82
If the bounce or instability is excessive, check:• Wire used for extension of the RTD should be three-wire, twisted and shielded with the shieldgrounded at the controller only. Each of the three lead wires must be of the same gauge.• The ideal installation has a separate conduit for the RTD leads (if they have been extended). Itis not usually a problem to run low signal levels in the same conduit as the power leads even inhigh-power applications, as long as the RTD wire is a twisted, shielded type with an insulationrating equal to or greater than the highest voltage in the conduit. Follow the proper ElectricalCode for your particular in-stallation.• Terminal connections that are not tight can add resistance to an RTD circuit. Check thetightness of all screw terminal connections at time of installation and during subsequentmaintenance checks.• Check the specifications for the particular cable being used to ensure that it does not haveexcessive capacitance when used in long lengths. This can cause a temperature offset betweenwhat the controller reads and what the RTD actually measures. This again is normally not aproblem since the controller compensates for all but the worst cases of this.• Lastly, it is possible for the RTD itself to fail on an intermittent basis but this failure modeshould be considered unusual. This kind of failure is probably the most difficult to find butfortunately it is also the least likely as a failure mechanism.6.2.3 GROUND FAULTGround-fault alarms can be due to incorrect installation as well as leakage resulting from wetsystem components or faulted cables.The 920 series switch interface detects ground faults by summing the outgoing and return tracecurrents through an internal current trans-former. Under normal operating conditions (no groundfault condition) this current will be zero. When there is a flow of current from one of the tracesupply wires to ground, a ground-fault condition occurs.If a ground-fault alarm is present on start-up of a new installation, it is likely due to a wiring erroror damaged cable. To verify this condition:• Check that the heating circuit neutrals return to the controller and are not connected directly tothe distribution panel. This can be a common problem if the installation is a retrofit situation.• On paralleled circuits, be certain that ALL neutrals return. The late addition of a circuit may notbe obvious.Use the monitoring feature available at the 920 Operator Console or the Model 780/GCC-9000Group Communications Controller to view the measured ground-fault current at the heattracecontroller. If this value is at the maximum that the controller can measure, it is usually anindication that the wiring is incorrect. If the value is less than 250 mAmps, an actual ground-faultcondition may exist in the cable.IMPORTANT: The controller monitors the integrity of the ground-fault (GF) detection transformerand associated wiring. If a fault is detected, the controller will report a GF value of 300 mAmps.THERMAL MANAGEMENT SOLUTIONS EN-DigiTrace920series-IM-H56874 04/1355 / 82
Page 6 and 7: Section I - Overview1.1 Controllers
Page 8 and 9: CSA C/US and c-ETL-us ApprovedThe 9
Page 10 and 11: 1.5.1 ENCLOSURE ASSEMBLYEnclosure A
Page 12 and 13: The user may want to consider enclo
Page 14 and 15: Temperature SensorsTerminal No.Poin
Page 16 and 17: 2.7.6 INPUT POWERThe 920 controller
Page 18 and 19: Section 3 - Programming and Configu
Page 20 and 21: 3.5.2 ALPHANUMERIC TAG ASSIGNMENTPu
Page 22 and 23: Range: 0.3 to 100.0 amps(CURRENT TU
Page 24 and 25: 3.5.15 TS 1 HIGH LIMIT CUTOUTPurpos
Page 26 and 27: IMPORTANT:• Auto-cycling should a
Page 28: 3.6 Common Controller SetupThis is
Page 31 and 32: • This alarm must be enabled and
Page 33 and 34: Procedure: Enable or disable the al
Page 35 and 36: • If the user resets an alarm whi
Page 37 and 38: efore the corresponding alarm will
Page 39 and 40: the overcurrent trip limit and the
Page 41 and 42: the 920 control module, these param
Page 43 and 44: 3.10 Operator Console Functionsbut
Page 45 and 46: eset. All load-shedding parameters
Page 47 and 48: interface.IMPORTANT: The controller
Page 49 and 50: Section 5 - Control Modes5.1 Introd
Page 51 and 52: 5.3 Load Shedding Control ModeLoad
Page 53: Section 6 - Troubleshooting6.1 Oper
Page 57 and 58: 6.3 Common Alarms—What to look fo
Page 59 and 60: Section 7 - Maintenance7.1 Operator
Page 62 and 63: Appendix B Typical Enclosure Dimens
Page 64 and 65: B.3 Four-Point Assembly #10160-1254
Page 66 and 67: B.5 Twenty-Point Assembly #10160-04
Page 68 and 69: C.1.2 100Ω NICKEL IRON RTD WIRINGC
Page 70 and 71: C.3 Communication Wiring C.3 Commun
Page 72 and 73: C.5 External Input/Output Port Wiri
Page 74 and 75: Appendix E 100 Ω Platinum RTD Tabl
Page 76 and 77: Appendix G Factory Default/Configur
Page 78 and 79: Other Alarms Configuration Sub-Menu
Page 80 and 81: Other Alarms Configuration Sub-Menu
Page 82: WWW.THERMAL.PENTAIR.COMNORTH AMERIC

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