IRT CP Instruction manual

C.P. SENTINELAUTOMATIC TYPE
CATHODIC PROTECTION RECTIFIER
INSTALLATION, OPERATION, &
MAINTENANCE MANUAL
REV. 3.0 NOVEMBER,2004
SINGLE PHASE INPUT
MODEL:
CP – “ON” POTENTIAL CONTROL
CI – “IR FREE” POTENTIAL CONTROL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
15360 – 116 Avenue, Edmonton, Alberta, Canada T5M 3Z6
Phone: [phone] Fax: [phone]
Website: www.irtrectifier.com Email: [email protected]

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 1 of 22
INDEX
PAGE
INTRODUCTION 3
DELIVERY INSPECTION 4
PRE-INSTALLATION STORAGE 4
SAFETY PRACTICES 5
GENERAL INSTALLATION RECOMMENDATIONS 6
RECTIFIER CONNECTIONS AT SITE 7
RECTIFIER OPERATION MODES 8
THE SENTRY CONTROLLER 9
THE SILICON CONTROLLED RECTIFIER (SCR) 12
POTENTIAL CONTROL AND EXTERNAL IR DROP 13
GENERAL COMPONENT DESCRIPTION 14
INITIALENERGIZATION 16
REGULAR MAINTENANCE AND ADJUSTMENT 18
TROUBLESHOOTING 20
APPENDIX:
INCLUDES ELECTRICAL SCHEMATIC, RECTIFIER DATA SHEET, AND ANY
OTHER OPTIONAL INFORMATION

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 2 of 22
Copyright © IRT Integrated Rectifier Technologies Inc.
All rights reserved. Unauthorized copying and distribution prohibited by law.
The contents of this Manual are subject to change without notice

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 3 of 22
INTRODUCTION
Corrosion of underground structures (pipelines, well casings, etc.) is a process that occurs every
minute of every day. As such, continuous protection is required to effectively prevent damage that
could cost a company significantly in lost revenues, manpower, and equipment. The proper
selection, installation, and operation of a suitable corrosion prevention system can be crucial to
ensure that this costly damage does not occur. For well-coated structures, structures with small
surface areas, or where minimal Cathodic Protection is required, a “sacrificial” type corrosion
prevention system may be used. For poorly coated structures, structures with large surface
areas, or where a larger amount of Cathodic Protection is required, an “impressed current” type
corrosion prevention system is required. One key component of an impressed current corrosion
protection system is a Cathodic Protection rectifier. A rectifier is a device that is used to convert
“alternating current” (AC), as provided by the power utility, to “direct current” (DC), as is required
for Cathodic Protection. The rectifier should be selected based on the type of control required for
the specific application, the amount of Cathodic Protection required to provide effective
protection, and the reliability of operation in the subject environment. IRT Integrated Rectifier
Technologies, Inc. manufactures Cathodic Protection rectifiers that exceed industry standards for
superior corrosion prevention and, as such, an IRT rectifier unit is a smart investment for any
company.
IRT Integrated Rectifier Technologies, Inc. Cathodic Protection rectifiers and associated products
are designed by a knowledgeable engineering team with years of experience in the corrosion field
and manufactured by skilled technicians with a dedication to quality. The IRT units are designed
with superior components to provide a high quality, reliable rectifier with an economic cost for
your application. IRT maintains a large volume of in-stock components and sub-assemblies to
ensure that orders can be shipped to you in the shortest time frame possible.
IRT products are sold and serviced by leading corrosion prevention engineering companies
throughout North America and Internationally. These companies have superior expertise in the
corrosion industry and have the personnel to meet all of your corrosion prevention system
requirements including design, installation, and maintenance. IRT products are also available
through leading material supply companies throughout North America.
Rectifiers manufactured by IRT Integrated Rectifier Technologies, Inc. are guaranteed against
defects in design, workmanship, or material for a period of one year from the time of shipment
from our facility. Please refer to our warranty statement for further details.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 4 of 22
DELIVERY INSPECTION
Although the rectifier unit may not be scheduled for immediate installation, we recommend that
it be thoroughly inspected, both externally and internally, upon receipt to ensure that no
damage has occurred during shipment. Please remember that although the outside of the
rectifier packaging may not show any signs of damage, there may be internal damage that will
not be apparent until the outer packaging is removed. Any damage, whether internal or
external, must be reported to the freight carrier immediately. If any damage has occurred
during shipment; an indication of this should made on the freight paperwork, the shipment
should then be accepted, and a claim filed with the freight carrier. Please ensure to retain the
original packaging that may indicate how the damage occurred.
If damage has occurred during shipment and repairs or a return to the factory is required,
please contact us, or your local IRT distributor, with the Serial Number and the Model Number
of the rectifier. This information is crucial for us to determine the rectifier unit in question and to
be able to provide suitable assistance. A Return Materials Authorization (RMA) number must
be obtained from the factory prior to return of any damaged rectifier units.
PRE-INSTALLATION STORAGE
If the rectifier unit is to be stored prior to installation, it is recommended that it be stored in a dry
area, preferably indoors. If the unit is to be stored outdoors for an extended period of time, it is
recommended that it be placed on a raised surface (pallet or platform) and covered with a
protective sheet or tarp to ensure the packaging does not deteriorate due to rain or snow.
Whether stored indoors or outdoors, the unit should be placed in an area where it is protected
from accidental damage from moving vehicles or equipment. Ensure that the rectifier unit is
transferred to and from the storage facility using proper handling techniques.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 5 of 22
SAFETY PRACTICES
This symbol denotes a possible shock or electrical hazard.
DO NOT INSTALL, REMOVE, or REWIRE
THIS EQUIPMENT WITH POWER APPLIED!!
As Cathodic Protection rectifiers are connected to the AC utility power, electrical shock hazards
are present within the rectifier units. It is recommended that only qualified electronic or electrical
personnel operate and maintain these units and that those personnel familiarize themselves with
the areas of possible hazard within the unit. Following these practices can enhance the safety of
personnel.
1.) Prior to site maintenance or inspection, familiarize yourself with the rectifier and
conditions at the site.
2.) Prior to doing any maintenance or troubleshooting on a rectifier unit, familiarize
yourself with any possible hazard points within the unit by reviewing the electrical
schematic and the physical layout of the rectifier.
3.) Whenever possible, set the AC disconnect from the power utility to the “OFF” position
prior to starting any work on the rectifier unit. Even with the rectifier AC input circuit
breaker in the “OFF” position, hazardous voltages are still present at any terminals
connected to the rectifier AC input terminals. Always tag and lock out the disconnect
to ensure others do not energize it while you are completing the rectifier work.
4.) Prior to opening the rectifier enclosure door, lightly touch the back of your hand to the
enclosure latch. If you feel an electrical tingle, set the fused AC disconnect to the
“OFF” position and contact an electrician for assistance.
5.) When taking readings across the rectifier terminals, it is recommended to use only
one hand, if possible.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 6 of 22
GENERAL INSTALLATION RECOMMENDATIONS
To ensure reliable, long-term operation of the Cathodic Protection rectifier, proper installation
of the unit is required. Though most installation sites differ, there are several key guidelines
that should be followed.
a) Prior to installation, check the connections (especially the electrical connections) on the
rectifier unit to ensure that nothing has become loose during shipment. It is also
recommended that if any scratches occur to the enclosure during installation, that
these points be touched-up to prevent corrosion on the enclosure.
b) Selecting the site of installation is a very important factor. The rectifier should be
installed in a location that is easily accessible by company personnel for regular
adjustment, monitoring, and maintenance. However, it should not be located in areas
where unauthorized personnel have easy access to the unit and may damage or
vandalize it (i.e. residential areas, playgrounds, farm yards, etc.). The convenient
access to AC power and the cathodic protection DC connections must also be
considered when choosing the rectifier location.
c) Proper ventilation and cooling of the rectifier unit is essential and must be considered
when choosing a suitable location. Air-cooled rectifiers are cooled by the natural
convection of cool air drawn into the bottom of the rectifier enclosure, passing over the
internal components, and the resultant warm air expelled from the top or sides of the
enclosure. Oil-cooled rectifiers are cooled by the natural circulation of oil from the
bottom to the top of the rectifier tank, over the internal components, and the resultant
heat is radiated from the upper walls of the rectifier tank. As such, when choosing the
installation site for the rectifier, adequate spacing should be allowed for around the
sides of the rectifier unit. The rectifier should not be located near sources of heat such
as exhaust vents, power generators, etc. If possible, place the rectifier unit in an area
where it will be shaded during the hottest part of the day. If the rectifier is to be installed
in an area with a high ambient temperature and minimal natural shading, a protective
sunshade is recommended.
d) The rectifier unit should be mounted on a secure surface. Ensure that the wall, pole,
frame, or mounting pad is designed to hold the full weight of the rectifier unit.
e) If the rectifier is to be installed in an area subject to frequent lightning activity,
upgraded, high-energy type surge arrestors are recommended. If possible, do not
locate the rectifier on a hill top where there increased chances of lightning strikes. Use
of a low resistance ground rod(s) is recommended. Locate the ground rods adjacent to,
but away from the rectifier, the ground bed, and incoming CP cables. Remember, most
damaging voltage surges are the result of induced pickup rather than a direct strike.
f) Do not install other equipment on or inside the rectifier enclosure without prior consent
from the factory. Unauthorized equipment installation will invalidate the rectifier
Warranty, as IRT has no control of the equipment added or the resultant detrimental
affect to proper rectifier cooling / operation.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 7 of 22
RECTIFIER CONNECTIONS AT SITE
DO NOT INSTALL, REMOVE, or REWIRE
THIS EQUIPMENT WITH POWER APPLIED!!
After the rectifier has been installed in a suitable location, have a qualified electrician connect
the rectifier unit to the AC supply following local and national codes. Please note that most
electrical codes require a disconnect device between the AC power supply and the rectifier.
Ensure that for dual AC input rectifiers (115 / 230 or 230 / 460 VAC), that the AC input terminal
jumpers are properly configured for the actual AC input voltage being supplied and that the AC
input wires are connected to the correct AC input terminals.
The grounding rod(s) should be connected to the ground lug terminal adjacent to the AC input
terminals within the rectifier.
Next, connect the cable(s) from the anode bed to the RECTIFIER POSITIVE output lug
terminal(s) and the structure cable(s) to the RECTIFIER NEGATIVE output lug terminal(s).
Ensure that these cables are suitably sized for the expected current and the length of the
cable run. Also, it is absolutely imperative that the polarity of DC connections is correct. A
reversal of the DC cables can actually cause accelerated corrosion and eventually, severe
damage to the structure to be protected.
C.P. SENTINEL Automatic Potential Controlled Rectifiers require two additional connections
for proper operation, the Reference Electrode and the Structure Sensing leads. Connect the
Reference Electrode to the rectifier terminal marked “REFERENCE” (REF) and the Structure
Sensing lead to the terminal marked “STRUCTURE” (STR.). The Structure Sensing lead must
be a separate non-current carrying lead connected to the protected Structure, usually adjacent
the Reference Electrode.
APPLICATION NOTES:
1. Superior Potential Mode control is achieved by minimizing noise on the lead wires
used for the REFERENCE Electrode & STRUCTURE sensing. It is recommended that
lead lengths in excess of 25 feet or leads in noisy electrical environments be shielded
in a separate conduit, or consist of shielded, twisted-pair conductors installed using
recommended shielding practices.
2. C.P. SENTINEL Automatic Potential controlled rectifiers are equipped with “Loss-of-
Reference” shutdown feature. Upon degrading or failure of the Reference Electrode,
internal cell resistivity increases, and the voltage “reference” decreases. The natural
condition for an automatic potential rectifier is to increase to full output to counter the
reduced voltage sensed. This feature is designed to prevent structure coating failure
due to excessive polarization if this cell failure condition occurs. If this type of rectifier is
to be used in Current or Voltage Modes without a Reference Electrode attached, it will
be necessary to jumper the REFERENCE- STRUCTURE hook-up terminals of the
rectifier. The rectifier REFERENCE SELECT switch must be set to sense an active and
functional Reference Cell input, or no output will occur from the unit. A “Loss-of-
Reference” shutdown will be evident by the analog Potential Meter reading full scale or
if equipped with a digital Potential Meter reading overload; first digit a “1” followed by
remainin
g
di
g
its blank.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 8 of 22
RECTIFIER OPERATION MODES
Depending upon the Model and the Options supplied with the rectifier, the C.P. SENTINEL
Automatic Rectifiers are available with the following modes of operation:
CONSTANT VOLTAGE MODE: (SUPPLIED ON ALL MODELS)
In this mode the rectifier control circuitry automatically adjusts the rectifier output to maintain
the VOLTAGE at the preset level. In this mode, the Current Set potentiometer determines the
current limit. When operating in this mode, the RED LED is illuminated.
CONSTANT CURRENT MODE: (SUPPLIED ON ALL MODELS)
In this mode the Rectifier control circuitry automatically adjusts the rectifier output to maintain
the CURRENT at the preset level. In this mode, the Voltage Set potentiometer determines the
voltage limit. When operating in this mode, the GREEN LED is illuminated.
IR-FREE POTENTIAL MODE: (OPTIONAL)
In this mode the Rectifier control circuitry automatically adjusts the rectifier output to maintain
the Reference Electrode to Structure POTENTIAL at the preset level. The Reference
Electrode to Structure POTENTIAL is maintained free of the error caused by current flow in the
anode-cathode circuit. IR-Free Potential mode is available on non-filtered single phase
rectifiers only. In this mode, the CURRENT Set potentiometer determines the current limit and
the VOLTAGE Set potentiometer determines the voltage limit. When operating in this mode,
the YELLOW LED is illuminated.
“ON” POTENTIAL MODE: (OPTIONAL)
In this mode the Rectifier control circuitry automatically adjusts the rectifier output to maintain
the Reference Cell to Structure POTENTIAL at the preset level. However, the Reference
Electrode to Structure POTENTIAL is maintained while there is current flow in the anode-
cathode circuit. In this mode, the Current Set potentiometer determines the current limit and
the Voltage Set potentiometer determines the voltage limit. When operating in this mode, the
YELLOW LED is illuminated.
MANUAL MODE: (OPTIONAL)
Rectifiers equipped with this option are supplied with a conventional manual tap-adjusted
transformer in addition to the automatic control circuitry. This mode permits the operator to
control the rectifier output by gating ‘on’ the Silicon Controlled Rectifiers to conduct as
conventional diodes. Manual rectifier output control is achieved by switching the Automatic-
Manual Switch to the Manual mode position and then adjusting the transformer secondary
taps.
NOTE:
C.P. SENTINEL Automatic Rectifiers encompass full galvanic isolation of the Reference
Electrode and Structure input signals. Therefore it will be necessary to connect separate
lead wires for the REFERENCE Electrode and STRUCTURE sensing.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 9 of 22
THE SENTRY CONTROLLER
The C.P. SENTINEL Automatic Rectifiers are controlled by the IRT SENTRY Controller. Refer
to the following layout of the SENTRY Controller for location of controls and jumpers:
FIGURE 1.0 SENTRY CONTROLLER (FOR BOARD REV. 2.0)
NOTE:
This section will describe the Controls, Jumpers, Test Points and Adjustments of interest
for field setup and operation, as performed by QUALIFIED TECHNICAL PERSONNEL. All
Remaining Factory Settings & Calibrations SHOULD NOT be attempted or tampered with.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 10 of 22
CAUTION!!
Do NOT attempt to alter the settings of any other trim pots on the controller board. These
are factory calibrations and tampering with these settings could jeopardize proper operation
and scaling of the SENTRY Controller.
CONTROLS:
Voltage, Current, and Potential settings are adjusted via three potentiometers available on the
SENTRY Controller. These potentiometers are 20-Turn trim-pots located at the end of the
controller board opposite the wiring connectors. (Refer to Figure 1.0, Page 9).
VOLTAGE: Rectifier output voltage (or Voltage Limit) is set by potentiometer “RV411”.
Rectifier operation in Voltage Mode or Voltage Limit will be indicated by the Red LED
“LED491”, adjacent the Voltage Set Potentiometer.
CURRENT: Rectifier output current (or Current Limit) is set by potentiometer “RV431”.
Rectifier operation in Current Mode or Current Limit will be indicated by the Green LED
“LED492”, adjacent the Current Set Potentiometer.
POTENTIAL: On rectifiers equipped with this option: Rectifier Structure to Reference
Electrode Potential is set by potentiometer “RV451”, in conjunction with the “Press-to-
Set/Actual” selector switch. Rectifier operation in the Potential Mode will be indicated by the
Yellow LED “LED493”, adjacent the Potential Set Potentiometer. Both Potential Set Point and
Actual Structure-Reference Electrode potential may be read on the rectifier’s potential meter
via the “Press-to-Set/Actual” selector switch.
JUMPER SETTINGS:
The SENTRY Controller is designed to adapt and accommodate a wide variety of field
installations and control situations. To make this accommodation easier, please review the
following Jumper functions and settings:
A. INPUT VOLTAGE SELECTION (JP601, JP602, & JP603)
INPUT
VOLTAGE JP601 JP602 JP603 COMMENT
115 VAC INSTALLED INSTALLED OMITTED DEFAULT POSITION
230VAC OMITTED OMITTED INSTALLED OPTIONAL POSITION
NOTE:
Depending upon the model and/or configuration of the rectifier ordered, one or more of
these potentiometers may be mounted external of the controller board on the rectifier
instrument panel. Consult your Rectifier Specification Sheet.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 11 of 22
B. PROGRAM MODES (JP231) USE WITH FIRMWARE VERSION 16C622AS-1.00
C: EXTERNAL INTERRUPT (JP241)
D: POTENTIAL MODE SETTINGS
E: VOLTAGE RANGE SETTINGS: “JPR411”
Header “JPR411” is factory set to determine the available output range of voltage control.
OTHER CONTROLLER PARTS & FUNCTIONS
FUSE: “F601” is located on the circuit board near the board-mounted control transformer.
This a 0.125 ampere, slow-blow type of 5mm x 20mm metric style fuse. Replace with same
fuse type and rating.
POWER ON LED: Controller “POWER ON” operation is indicated by “LED231”, Yellow
WIRING CONNECTORS: “TB101” & “TB102”. These are 14-pin plug on connectors. Ensure
all wiring connections are secure by tightening the screw terminals on these connectors.
“JP231” SETTING FUNCTION COMMENT
JP231 – 1 (TRIG) NOT SUPPORTED NOT USED
JP231 – 2 (Rsamp) INSTALLED: Reference Electrode
Sampled just prior to SCR Gate-on DEFAULT: Use in IR-Free mode & Choke Filtering
JP231 – 2 (Rsamp) REMOVED: Reference Electrode Sampled
after Zero-Crossing AC waveform Use with AC Interference
JP231 – 3 (SF A) Doubles SCR Gating “ON” & “OFF” times INSTALLED (DEFAULT)
JP231 – 4 (SF B) Doubles the “SF-A” SCR Gating “OFF” time INSTALLED (DEFAULT)
“JP241” SETTING FUNCTION
JP241 PINS 1 - 2 Normally Closed contacts = Rectifier output current (Optional Setting)
JP241 PINS 2 - 3 Normally Open contacts = Rectifier output current (Default Setting)
JUMPER FUNCTION – DESCRIPTION COMMENT
JPR311, PINS 1-2 “Loss of Reference Shutdown” Enabled INSTALLED
JPR331, PINS 1-2 Select Type of Reference Cell = CU-CUSO4or Ag-CL DEFAULT
JPR331, PINS 2-3 Select Type of Reference Cell = ZINC OPTIONAL
JPR341, (CLOSED)
JPR362, (OPEN) Select Low Range (Max. Potentials less than ± 3.0 Volts) OPTIONAL
JPR341, (OPEN)
JPR362, (CLOSED) Select High Range (Maximum Potentials > than ± 3.0 Volts) DEFAULT
JPR361, PINS 1-2 Select Continuous “ON-Potential” Control & Sampling DEFAULT

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 12 of 22
THE SILICON CONTROLLED RECTIFIER (SCR)
Automatically controlled rectifiers utilize phase control of the
supplied 50 or 60 Hertz AC voltage using a solid-state device
called a Silicon Controlled Rectifier (SCR). This device is
similar to a conventional diode, but is equipped with an extra
terminal for control called the GATE. Although akin to a diode,
this device has unique properties of being able to block
conduction of current when the device is forward biased until
an appropriate signal is applied to the Gate terminal. Once the
appropriate gate signal is applied, the SCR remains in
conduction while forward biased, or until the current trough the
device goes to almost zero.
The control of the rectifier DC output is accomplished by “gating
on” the SCR at the point in the AC waveform necessary to
produce the desired output. This output can be the regulated
DC Voltage, the DC Current, the Structure to Reference
Electrode Potential or a combination of the three modes of
control. A minimum of two SCR’s are required to achieve full control over the AC waveform. The
two SCR’s are configured with two diodes into a full-wave bridge configuration.
Often SCR’s and diodes are combined into full-wave controlled
rectification modules. Typically the modules used are comprised
of two SCR’s and two diodes with the cathodes of the 2 SCR’s
connected to the module Positive (+) terminal. SCR-Diode
modules are then mounted to a suitably sized heatsink for
cooling.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 13 of 22
POTENTIAL CONTROL AND EXTERNAL IR DROP
In applying and operating IR-Drop Free C.P. SENTINEL Automatic Rectifiers, it is important
that Cathodic Protection personnel are familiar with the methods & principles of using this type
of rectifier to mitigate corrosion. Briefly described as follows:
Current flowing in the measurement circuit will cause a voltage drop (referred to the Ohm’s
Law equivalent of Current “I” multiplied by Resistance “R” or “IR”), which becomes
incorporated into measurements as an error. In addition, any external currents flowing through
the electrolyte in the area between the reference electrode and the structure will cause their
own voltage drop, which also becomes part of the measurement as an additional error.
Cathodic protection systems and AC & DC electrical power systems are some of the possible
sources of these currents. The magnitude of errors from external IR drops can be substantial.
To accurately maintain the required polarization potential on a given structure, these errors
must be minimized during the design phase and then eliminated by electronic circuitry within
the SENTRY Controller, which is used in the C.P. SENTINEL Automatic Rectifiers.
The SENTRY Controller removes the IR drop error from the potential measurement by
interrupting the cathodic protection current supplied by the rectifier momentarily. This action
produces an instantaneous voltage drop, which is considered to be the external IR Drop. The
potential from Reference Electrode to Structure is measured immediately after this
instantaneous drop, and is considered to be the "IR Drop Free" potential of the structure.
Clearly, this method only works with an impressed current cathodic protection system where
all the rectifiers on that system can be interrupted simultaneously, and there are no other
sources of current flowing through the electrolyte.
An issue that should be considered when using current interruption for instant-off
measurements is: What is meant by instantaneous? The answer is not simple since it depends
upon the structure, the electrolyte and the method of interrupting the current. Putting the
answer in electrical terms, it depends upon the capacitance and the inductance of the circuit.
IR drop free measurements can be made microseconds after current interruption on small,
uncoated specimens in a low resistance electrolyte. Large coated structures, such as
pipelines, or high resistance electrolytes, such as concrete, usually require several hundred
milliseconds or more for IR-drop free measurements. Interrupting current on the AC side rather
than on the DC side of the rectifier will increase the time delay because the circuit inductance
is higher. An oscilloscope should be used if measurement precision is necessary; it should be
either battery powered or connected through an isolation transformer to eliminate ground
loops.
NOTE:
This section applies only to C.P. SENTINEL Automatic Rectifiers which have been ordered
and manufactured to function as IR-Drop Free Reference Electrode controlled outputs.
Consult your Rectifier Specification Sheet.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 14 of 22
GENERAL COMPONENT DESCRIPTION
When operating any equipment, it is a good practice to become familiar with the key
components and the general operation of that piece of equipment. The following is a summary
of the key components of a rectifier and their function:
The AC Input Surge Arrestor is a device that protects the rectifier components from voltage
surges that may occur across the AC input of the rectifier. It does this by providing a bypass
circuit for the resultant current from these high voltage surges after a specific voltage threshold
has been reached. Most surge arrestors are designed to handle a certain number or energy
value of surges prior to failing.
The rectifier AC Input Circuit Breaker (CB1) is a fully magnetic type that serves three key
functions. It is used as an “OFF-ON” switch for the rectifier, it provides “short circuit”
protection, and, to a lesser degree, provides input overload protection.
The rectifier Main Transformer (T1) provides full electrical isolation between the utility AC
power and the Cathodic Protection DC circuit. It also steps the voltage up or down as required
for the DC circuit and, for tap type units, provides a means of output adjustment.
The rectifier AC Secondary Fuse is a time lag or slow-blow type that provides protection from
not only short-circuits or overloads in the DC output circuit but also in the diode bridge circuit.
The rectifier SCR-Diode Bridge Assembly is comprised of silicon controlled diodes (SCR’s)
and diodes configured into a full-wave bridge configuration. The SCR-diodes are supplied with
suitably sized heatsinks to ensure that the SCR-diodes do not exceed 100°C at full rated
output. The SCR-diode bridge controls and rectifies the AC secondary voltage of the
transformer into DC voltage that can be used for Cathodic Protection. This DC voltage level is
then automatically maintained by the SENTRY Controller in Potential, Current or Voltage
Mode, as set by the operator.
A Varistor is supplied across the AC input to the diode bridge to provide additional protection
from any voltage surges that may pass the main AC surge arrestor or be developed by the
main transformer. A second varistor may also be supplied across the DC output of the diode
bridge at special request.
The Current Monitoring Shunt is a block style calibrated resistor with an accuracy of 0.25%.
The DC current and voltage rating are stamped into the body of the shunt. Shunts used in
rectifiers equipped with digital meters will be either 1 Millivolt or 10 Millivolts per ampere,
depending upon the rectifier output current rating.
The rectifier Ammeter & Voltmeter utilize an analog, taut-band type movement that provides
±2% accuracy. The DC output amperage of the rectifier is monitored by a meter connection
across the calibrated test screws of the above shunt. The DC output voltage of the rectifier is
monitored by a meter connection across the DC output terminals of the rectifier.
On Potential Controlled rectifiers, an additional Potential Meter is supplied to monitor the
Structure to Reference Cell Potential, and the desired “Set Potential”. This meter receives the
potential reading from the SENTRY Controller.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 15 of 22
Potential Adjust Potentiometer is a front, panel-mounted multi-turn potentiometer used to
set the required Structure to Reference Electrode potential required by the CP System. The
setting can be read on the Potential Meter by activating the Potential Switch to the “Set”
position.
The “Set-Actual” Switch permits the operator to monitor, via the rectifier Potential Meter,
either the “Actual“ potential or the “Set” potential of the rectifier. The “Actual” potential may be
either free of IR-Drop error, as determined by the SENTRY Controller, or the “ON” potential, if
the rectifier is equipped with filtering or if configured to operate in the ”ON” potential Mode.
Metering Test Points (Optionally supplied) are located on the touch-safe instrument panel for
purposes of verifying the digital meter readings. Metering Test Points are 0.093 diameter test
jacks, with polarity and function as indicated by the silk screening on the panel. The “Potential”
test points will indicate the potential voltage reading as determined by the “POTENTIAL
ACTUAL/SETPOINT” toggle switch.
The Reference Electrode (Cell) – Structure Input Terminal Block is used to make field
connections to the CP system Reference Cell and Structure sensing leads.
External Interrupt Terminal Block: (NOT Supplied on IR-Free rectifiers) Two terminals are
provided on the front panel of the rectifier for purposes of interrupting the rectifier output using
the SENTRY Controller. Jumper “JP241” on the controller board as required for Normally
Open equals rectifier “ON” or Normally Closed contacts equals “rectifier “ON” as dictated by
the interrupter being used. This is the preferred method to interrupt the rectifier by an external
means. Special circuitry in the SENTRY Controller retains all of the operating parameters for
resumption of control parameters after conclusion of an interrupt procedure and will not reset
the slow start circuitry.
The DC Output Surge Arrestor is a device that protects the rectifier components from voltage
surges that may occur across the DC output of the rectifier. It’s operation and characteristics
are similar to the AC input surge arrestor.
As many optional features / components are available for our customers, it is not practical for
this manual to describe all of the possible options in detail. As such, it is recommended that
the rectifier data sheet and the electrical schematic be reviewed in detail to become familiar
with any features not detailed in this manual.
APPLICATION ALERT!!
IR-Free Automatic Potential controlled rectifiers typically do not utilize external interrupters
when operating. For proper IR-Free potential control, the SENTRY Controller must not be
impeded by external interrupter cycles as it controls the desired “Set Potential” of the CP
system.
NOTE:
If no reference electrode is used, a jumper should be placed across these input terminals.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 16 of 22
INITIAL ENERGIZATION
After the rectifier has been properly connected to the AC supply and the DC output cables,
(and Reference Electrode – Structure Sensing leads in the case of a potentially controlled type
of rectifier) it is ready to be energized. Before energizing, always double-check both the AC
and DC connections to ensure they are properly connected. Ensure that for dual input
rectifiers (115 / 230 or 230 / 460 VAC), the AC input terminal jumpers are properly configured
for the actual AC input voltage being supplied and that the AC input wires are connected to the
proper terminals. For Current Controlled rectifiers, ensure that the rectifier is at its lowest
control setting, by adjusting the “Current Adjust” potentiometer to zero. Use a multi-meter to
verify static Reference Electrode – Structure potentials and record for later reference.
ENERGIZATION ALERT!!
If the rectifier is to be used on a CP system protecting the inside of a vessel
ensure the vessel contains fluid sufficient to cover the anode system and the
Reference Electrode.
Place the AC fused disconnect switch to the “ON” position and measure across the rectifier AC
input terminals to ensure the voltage present is as expected. Next, place the rectifier AC input
circuit breaker also to the “ON” position. The “POWER ON” Yellow LED on the SENTRY
Controller will illuminate. The SENTRY Controller is designed with a “slow start” circuitry to
minimize in-rush currents and to prevent the rectifier from starting at full output. This slow start
time period will last from 3 – 10 seconds. There will be some deflection on the panel meters,
especially the Potential Meter (although this deflection may be quite minimal on the Ammeter
and Voltmeter). For units with a metering switch, ensure to set this switch to the “ON” position.
For Automatic Current rectifiers, simply adjust the “Current Adjust” potentiometer to the
required current. This current will be read on the rectifier Ammeter. The rectifier ammeter can
be verified by measuring the voltage (in Millivolts) across the calibrated test screws of the rectifier
shunt (not across the connection bolts). To determine the current through the shunt from the
millivolt reading taken, the following formula can be used:
DC Current (I) = Measured Shunt Voltage (Millivolts) X Rated Shunt Current
Rated Shunt Voltage (50 Millivolts typical)
Note: Rated shunt current and voltage values are stamped onto the body of the shunt
and are also shown on the rectifier data page.
The ammeter can also be verified with an external DC clamp-on type meter, if available.
It is recommended that all initial energization readings be recorded for future reference. Useful
readings to record are structure potential levels prior to energization, AC input voltage &
current, DC output voltage and current, tap or adjustment dial setting, structure potential levels
after energization, as well as any observed problems or possible future concerns with the
installation, in general.
For Automatic Potential Rectifiers, activate the Potential Switch to the “SET” position and
observe the “SET” level of potential control on the Potential Meter. Adjust the required
potential control level with the Potential Adjust potentiometer to the desired level of control.
Release the Potential Switch and observe the “Actual” potential on the Potential Meter. When
operating in this mode, the Yellow LED will be illuminated. It is important to note that if the

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 17 of 22
A NOTE ABOUT POTENTIAL READINGS!!
The SENTRY Controller is designed to provide IR-Free potential readings for control and
for display to the Potential Meter. This reading will differ from the measured Structure–
Reference Electrode inputs into the rectifier by the IR-Drop error. (Refer to description on
Page 13) The “Actual” potential from the SENTRY Controller will only correspond to the
measured Structure–Reference Electrode inputs into the rectifier with no current flowing;
i.e.: at no load. On rectifiers equipped with efficiency filters, true IR-Free operation cannot
be attained. The “Actual” potential will equate to the Structure–Reference Electrode
potential with minimal IR-Free error.
potential control “Set” level cannot be initially attained due to the polarization time of the
Structure, the rectifier will ramp up the DC output to either the Voltage set point (Voltage Limit;
Red LED illuminated) or the Current set point (Current Limit; Green LED illuminated). Once the
potential control “Set” level is attained, the SENTRY Controller will automatically revert into
Potential Mode and maintain the Structure to Reference Electrode potential at the preset level.
The Yellow LED will then be illuminated.
Rectifiers equipped with MANUAL MODE Option: Adjustment of rectifiers equipped with this
option requires the “Automatic-Manual” selector switch be switched to the “Manual” position.
Start the rectifier with the Coarse & Fine taps set to their lowest level (Coarse “A” – Fine “1”).
Observe and record if necessary the rectifier output currents and voltage levels, and the
polarization level of the Structure being protected. Incrementally, increase the transformer tap
settings until either target current or polarization levels are attained. The SENTRY Controller is
NOT required for manual mode, and may be removed for repair if it is not functioning correctly.
After the structure potential readings have been taken and prior to leaving the site, it is
recommended that the DC output connections to the rectifier be rechecked to ensure a secure
connection. It is also beneficial to recheck the rectifier to ensure that all air inlet and outlet venting
on the enclosure is not obstructed in any manner. The rectifier O&M manual should be securely
set in it’s holder (for small rectifiers without a manual holder, it is recommended that the manual
be kept with the main operator or in the control room of the closest station). Also verify that all
holes within the enclosure (other than the venting screens) are suitably plugged (such as unused
conduit knockouts). For rectifier units with “OFF-ON” meter switches, ensure that the switch is in
the “OFF” position prior to leaving the site.
APPLICATION NOTES:
1. Remember, the C.P. SENTINEL AQUA-LINE rectifiers are equipped with “Loss-of-
Reference” shutdown feature. The rectifier “REFERENCE SELECT” switch must be
set to sense an active and functional Reference Cell input or no output will occur from
the unit. Alternately, jumper the “REF. CELL” inputs on the front of the rectifier panel
to obtain a current output. A “Loss-of-Reference” shutdown will be evident by the
digital Potential Meter reading overload; first digit a “1” followed by remaining digits
blank.
2. To function in current mode up to rated current, the output of the rectifier cannot be
limited by either the “VOLTAGE SET” or the “POTENTIAL SET” potentiometers.

C.P. SENTINEL AUTOMATIC TYPE CATHODIC PROTECTION RECTIFIER MANUAL
INTEGRATED RECTIFIER TECHNOLOGIES, INC.
Doc #: APC0010
Rev. 3.0, November, 2004
Page 18 of 22
REGULAR MAINTENANCE & ADJUSTMENT
The basis for any effective CP system is routine documentation & maintenance. Despite the
rectifier maintaining the DC output “automatically”, it is recommended that the rectifier be
checked and adjusted if necessary at least twice per year. Some local regulatory bodies
require a monthly or semi-monthly check to ensure proper protection levels are being
maintained. These checks also allow you to ensure that the rectifier has not been damaged.
When completing this maintenance and adjustment check, it is recommended that all readings
and observations be recorded in the site file. With regular maintenance checks and by
maintaining good records, future troubleshooting and repair costs can be reduced.
Prior to arriving at the site for the rectifier maintenance check, it is recommended that the
technician review the existing rectifier site file to gain familiarization with the subject rectifier
and site conditions. Upon arriving at the rectifier site, a visual check should be completed to
determine if any changes have occurred. Things to look for are signs of new underground
construction, buildings, pipeline tie-ins, bonds, etc. Prior to adjustment of the rectifier, it is
recommended that structure potential readings be taken, to determine the adjustment level
required. Even if the potential levels are within the required range, the rectifier should still be
checked for proper operation.
When approaching the rectifier, ensure that no items have been placed near the rectifier
enclosure in such a manner as to block the venting, either on the bottom or sides. As the vent
openings on the rectifier enclosure are screened, there should be no refuse inside from birds
or larger insects. However, after opening the door of the enclosure, ensure that there has been
no significant accumulation of dirt, snow, or other small debris at the bottom of the enclosure,
which may adversely affect proper venting.
DO NOT INSTALL, REMOVE, or REWIRE
THIS EQUIPMENT WITH POWER APPLIED!!
Prior to any adjustment of the rectifier, measure and record the “As Found” readings of the
rectifier (DC voltage, DC amperage, etc.). Next, set the rectifier circuit breaker and the utility
disconnect to the “OFF” position to allow for a detailed rectifier inspection.
At least once a year the rectifier should be inspected for loose electrical connections that could
eventually cause damage to the electrical panel, wiring, or rectifier components. If an electrical
connection becomes loose, the resistance of the connection increases and causes it to heat
up. This additional heat will cause the connection to oxidize and become even higher resistant
until a failure occurs. The best way to check for a heated connection is with a temperature
probe, however, as these are not typically standard issue for Cathodic field maintenance, the
visual inspection method will suffice. First, visually inspect all of the main electrical
connections within the rectifier for signs of discoloration on the connection terminal, the
electrical panel, or the wire attached to the terminal. Key points to check are the DC output lug
terminal connections and the fuse holder connections. If you see a suspect connection, use a
wrench or other suitable tools to see if the connection is indeed loose. (Note: Be careful when
touching these types of connections with your hand as the temperature of loose high current
connections can cause a significant burn.) If you do find a loose connection, it should be
secured with suitable tools (make sure to secure both the front and rear of the double-nutted
panel connections). If a loose connection has already caused damage to the electrical panel,
the panel should be repaired or replaced, as re-tightening a connection on a degraded panel
will most likely still lead to a future failure.