Honeywell Searchline Excel Open-Path Release Note

Searchline Excel Infrared Gas Detectors
Open Path and Cross-duct
Technical Handbook

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Ensure that you read and understand these instructions BEFORE operating the equipment. Please pay
particular attention to the Safety Warnings.
WARNINGS
1. The Searchline Excel gas detector is certified for and intended for use in potentially hazardous
areas. Install and use the Searchline Excel gas detector in accordance with the latest regulations.
2. For installations in the UK, the Code of Practice SELECTION, INSTALLATION AND
MAINTENANCE OF ELECTRICAL APPARATUS FOR USE IN POTENTIALLY EXPLOSIVE
ATMOSPHERES should be strictly observed. General recommendations are given in BS 5345:
Part 1:1989. Specific requirements for flameproof (Type ’d’), intrinsically safe (Type ’I’) and increased
safety (type ’e’) protection are given in BS 5345: Part 3: 1979, BS 5345: Part 4:1977 and BS
5345: Part 6:1978 respectively. Consideration should also be given to BS EN 60079-14. Refer to
BS 6959:1988 in the UK or the appropriate local or national regulations.
3. For installations in North America, the national Electrical Code (NFPA 70 - 1990) or later issues
should be strictly observed.
4. Elsewhere, the appropriate local or national regulations should be used.
5. The Searchline Excel gas detector must be properly earthed to protect against electrical shock
and minimise electrical interference. For electrical installation design considerations refer to
Section˚3.
6. Operators must be fully aware of the action to be taken if the gas concentration exceeds an alarm
level.
7. Dismantling or repair of equipment should be carried out in the safe area only.
8. Test gases may be toxic and/or combustible. Refer to Material Safety Sheets for appropriate
warnings.
9. Do not drill holes in any housing as this will invalidate the explosion protection.
10. In order to maintain electrical safety, the unit must not be operated in atmospheres with more
than 21% oxygen.
11. Ensure that the bolts which secure flameproof enclosures are fully tightened. The securing bolts
used are made from a special certified grade of steel. Only bolts supplied by Zellweger Analytics
should be fitted for this purpose.
12. Do not open the enclosure in the presence of an explosive atmosphere.
13. The transmitter unit contains high voltages when operational. These are discharged when the
unit is removed from its enclosure.
14. The conduit and cable glands fitted to Searchline Excel should not be modified. If, however, it
becomes necessary to make modifications they must comply with the relevant national Codes of
Practice.
SAFETY

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CAUTIONS
1. Use only approved parts and accessories with the Searchline Excel gas detector.
2. To maintain safety standards, commissioning and regular maintenance of the Searchline Excel
gas detector should be performed by qualified personnel.
IMPORTANT NOTICES
1. Zellweger Analytics Limited can take no responsibility for installation and/or use of its equipment
if this is not done in accordance with the appropriate issue and/or amendment of the manual.
2. The user of this manual should ensure that it is appropriate in all details to the exact equipment to
be installed and/or operated. If in doubt, the user should contact Zellweger Analytics Limited for
advice.
3. Effect of explosive atmosphere on materials.
Searchline Excel is made from materials which exhibit good resistance to corrosive and solvative
substances. The Exd enclosures are made from 316 stainless steel and the explosion protected
windows are made from toughened soda lime glass. Zellweger Analytics are not aware of any
significant effects of explosive atmospheres upon these materials. Contact Zellweger Analytics
or one of their agents for specific queries.
ZellwegerAnalytics Limited reserve the right to change or revise the information supplied in this document
without notice and without obligation to notify any person or organisation of such revision or change.
If further details are required that do not appear in this manual, contact Zellweger Analytics Limited or one
of their agents.
SAFETY

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Every effort has been made to ensure the accuracy in the contents of our documents, however, Zellweger
Analytics Limited can assume no responsibility for any errors or omissions in our documents or their
consequences. Zellweger Analytics Limited would greatly appreciate being informed of any errors or
omissions that may be found in our documents. To this end we include the following form for you to
photocopy, complete and return to us so that we may take the appropriate action.
HELP US TO HELP YOU
Marked up copies attached (as appropriate): Yes / No
Please inform me of the outcome of this change: Yes / No
For Marketing Communications, Zellweger Analytics Limited:
Actioned By: Date:
Response: Date:
To: Marketing Communications
Zellweger Analytics Limited
Hatch Pond House
4 Stinsford Road
Nuffield Estate
POOLE. Dorset
BH17 0RZ
United Kingdom
Tel.: [phone]
Fax.: [phone]
E-mail : [email protected]
From:
Address:
Tel.:
Fax.:
E-mail:
I suggest the following corrections/changes be made to: ..................

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CONTENTS
SAFETY 2
HELP US TO HELP YOU 4
1. INTRODUCTION 7
2. OVERVIEW 9
2.1 Introduction 9
2.2 Transmitter 10
2.3 Receiver 11
2.4 Adjustable Mountings 13
3. INSTALLATION AND OPERATION 14
3.1 Introduction 14
3.2 Siting and Mounting 15
3.3 Electrical connections 19
3.4 Power supply 24
3.5 Unpacking 25
3.6 Installation procedure 28
3.7 Alignment and commissioning 34
3.8 System Controller calibration 49
3.9 Installation Checks/Tests 50
4. CROSS-DUCT EXCEL 57
4.1 Introduction 57
4.2 Gas Detector Description 57
4.3 Installation and Operation 58
4.4 Installation Procedure 61
4.5 Electrical Installation 65
4.6 Initialising the Excel Gas Detector 68
4.7 Maintenance 70
4.8 Problem Solving 72
5. MAINTENANCE 73
5.1 Inspection and Cleaning 73
5.2 Functional Checking 73
5.3 Calibration Check using the Gassing Cell 74
5.4 Display Gas Reading 75
5.5 Alignment Telescope 76
5.6 Operational Maintenance (FM) 76

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CONTENTS
6. PROBLEM SOLVING 77
7. SPECIFICATIONS 82
7.1 System 82
7.2 Detectable gases 83
8. CERTIFICATION 84
8.1 General 84
8.2 CENELEC 85
8.3 UL 91
8.4 CSA/FM 96
APPENDIX A - HANDHELD INTERROGATOR 100
A.1 Introduction 100
A.2 Overview 100
A.3 Connection to System 101
A.4 Basic User Tasks 102
A.5 Menus 103
A.6 Problem Solving 116
APPENDIX B - GLOSSARY 117
B.1 Terminology 117
B.2 Measurement Units 117
B.3 Abbreviations 118
APPENDIX C - ACCESSORIES & SPARE PARTS 120
C.1 System Units 120
C.2 General 120

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Searchline Excel is a hydrocarbon gas detection system that is available in two versions:
•Searchline Excel Open-Path Gas Detector
•Searchline Excel Cross-Duct Gas Detector
Searchline Excel Open-Path Gas Detector (OPGD) consists of a Transmitter unit that sends an
infrared beam to a Receiver unit up to 200 metres away, and can be located where a flammable
hydrocarbon gas cloud is likely to occur.
The Cross-Duct version of Searchline Excel is used where the path length is less than 5 metres,
for applications such as air intake ducts. Most of the installation and operating instructions for
the Open-Path Excel apply to the Cross-Duct Excel, but see Chapter 4 for specific information
about the Cross-Duct version.
Both types of gas detector operate on the principle of infrared (IR) absorption. Gases absorb
light at specific wavelengths depending on their molecular composition. Hydrocarbon gases
absorb in the infrared region of the spectrum. If a cloud of hydrocarbon gas is present, part of
the infrared light is absorbed by the gas, causing a reduction in the signal received that is
proportional to the amount of gas in the beam.
The Searchline Excel Transmitter unit produces the infrared light, and the Receiver unit features
optical detectors and signal processing electronics. Each unit is housed in a robust stainless
steel housing. The Receiver produces a 4 - 20mA analogue output equivalent to 0 - 5 LEL.m
(Lower Explosive Limit metres) of gas.
NOTE: THE INFRARED BEAM IS INVISIBLE AND EYE SAFE.
Searchline Excel is designed for use in the most demanding environments/applications and
provides a sensitive, fast and reliable response. The sophisticated open-path technology provides
immunity to sunlight and minimises the effects of environmental factors such as rain, fog, ice,
snow and condensation.
The Transmitter and Receiver units incorporate heated optics designed to minimise the build
up of humidity, condensation, snow or ice on the glass windows, that could obscure the optics
in extreme conditions.
The system is microprocessor controlled with integral self-diagnostics and fault finding facilities.
Local communication between an operator/technician and the gas detector system is made via
an associated Handheld Interrogator that uses the Receiver s inbuilt RS485 serial link. The
interrogator provides the user with a menu-style interface to select and invoke commands for
commissioning and configuring the system, and for viewing the system state and measurements.
The interrogator is connected to the Receiver via one of Zellweger Analytics’ DVC100/DX100/
DX100 (M) types of Termination Unit, or via other types of junction box using the optional SHC
Protection Device. The DVC100 and DX100 are passive junction boxes whereas the DX100
(M) features an active digital interface that allows a remotely located control centre to monitor
the gas detector’s signal output and perform basic commands using the Modbus Remote Terminal
Unit (RTU) protocol over an RS485 link.
1. INTRODUCTION

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This handbook consists of the following parts:
•Chapter 1 Introduction
•Chapter 2 System Description
•Chapter 3 Installation And Operation
•Chapter 4 Cross-Duct Excel
•Chapter 5 Maintenance
•Chapter 6 Problem Solving
•Chapter 7 Specifications
•Chapter 8 Certification
•Appendix A Handheld Interrogator
•Appendix B Glossary
•Appendix C Accessories & Spare Parts
Information notices
The types of information notices used throughout this handbook are as follows:
WARNING
Indicates hazardous or unsafe practice that could result in severe injury
or death to personnel.
Caution: Indicates hazardous or unsafe practice which could result in minor injury to
personnel, or product or property damage.
Note: Provides useful/helpful/additional information.
If more information beyond the scope of this technical handbook is required please contact
Zellweger Analytics.
Associated Documents
Searchline Excel Open-Path Infrared Gas Detector
Basic Installation Guide Part No: 2104M0510
Searchline Excel Cross-Duct Infrared Gas Detector
Basic Installation Guide Part No: 2104M0511
DX100 Series Termination Units Technical Handbook Part No: 2104M0701
1. INTRODUCTION

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2.1 INTRODUCTION
Each type of Searchline Excel gas detector consists of two units, a Transmitter and a Receiver.
This separate Transmitter/Receiver configuration provides the most reliable basis for open
path gas detection.
There are no transceiver units or retro-panels available for the Searchline Excel, except for the
Cross-Duct version, which is only for use between 0.5 and 5 metres path length. For a description
of Cross-Duct Excel, see Chapter 4.
PL612
(or other junction box)
Flexible conduit
DVC100/DX100/DX100 (M)
(or other junction box)
Mounting bracket
Pivot block
Monitored
path
5-200m
Mounting plate
Transmitter
Receiver
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There are five ranges of Searchline Excel gas detector. These are:
Open-Path Short Range 5 — 40m (15ft — 130ft)
Medium Range 20 — 120m (65ft — 390ft)
Long Range 120 — 200m (390ft — 650ft)
Cross-Duct Short Range: 0.5 — 2.5m (20in — 8ft)
Long Range: 2.5 — 5m (8ft — 15ft)
See Chapter 4 for details of the Cross-Duct Excel.
When designing an installation for Searchline Excel it is important that the correct range of the
gas detector for each path to be monitored is selected and specified.
Note: In order to avoid the problems associated with gas detectors being used beyond their
specified ranges or when incorrectly aligned, an Instrument Assisted Alignment (IAA)
procedure for Searchline Excel checks for correct gas detector type, operating range
and signal levels before allowing the gas detector to activate.
The Transmitter and Receiver are each mounted upon robust, adjustable mounting brackets.
These brackets bolt to a mounting plate, which is designed to accommodate a variety of junction
boxes, accessories and mechanical mounting configurations. The small size and flexibility of
Searchline Excel and its mounting arrangements are intended to make correct installation design
as simple as possible. Installation details are given in Chapter 3.
2.2 TRANSMITTER
The Searchline Excel Transmitter produces an intense, collimated infrared beam which is produced by a
Xenon arc flashlamp.
The flashlamp s infrared output is collimated using mirrors which enables a more uniform beam
(no chromatic aberrations) to be produced and hence reduces alignment sensitivity. In order to
prevent annoying visible flashes, the visible emissions from the flashlamp are blocked by a
filter.
The Transmitter s flashlamp is pulsed at precisely 4Hz, each pulse lasting for approximately
one microsecond. The precise timing and extremely short duration of these pulses give the
Transmitter a very distinctive signature. This distinctive signature makes it easy for the Receiver
to distinguish Searchline Excel Transmitter pulses from both natural and artificial sources of
infrared radiation.
NOTE: THE INFRARED BEAM IS INVISIBLE AND EYE SAFE.
The medium and long range Transmitters contain a higher power flashlamp and larger optics
than the standard short range unit. The resulting infrared beam is many times brighter which
allows for a considerable increase in operating range.
2. OVERVIEW

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160mm (SR)
211 (MR/LR)
417mm (SR)
433 (MR/LR)
291mm (SR)
353 (MR/LR)
Approximately
300mm
The Transmitter window is heated to minimise condensation, frosting and the build up of snow.
During particularly cold operating conditions, the heating of the Transmitter window is increased
to turbo levels. The turbo mode can be disabled if not required.
Electrical connections to the Transmitter are made via wires which run through the protective,
flexible conduit. There are three Transmitter wires, red (+24V), black (0V) and greenIyellow (GND).
2.3 RECEIVER
The Searchline Excel Receiver collects infrared radiation from the Transmitter and performs
measurements to enable hydrocarbon gases in the beam path to be detected.
Infrared radiation is collected by a single, silicon lens, which is common to both the sample and
reference measurement channels. This radiation is divided by a beamsplitter and fed to two
filtered detectors, sample and reference.
The sample detector input is filtered at wavelengths where strong infrared absorption is exhibited
by the target gas. The reference detector input is filtered at nearby wavelengths, where strong
infrared absorption is not exhibited by the target gas. By calculating the ratio of the sample to
reference signal it is possible to measure the quantity of gas in the beam, whilst compensating
for the effects of rain, fog, dirt etc.
2. OVERVIEW

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160mm417mm
291mm
Approximately
300mm
The solid state, photovoltaic detectors used in Searchline Excel provide an exceptional dynamic
range and superb temperature and long term stability. These features contribute strongly to the
solar immunity and stability of Searchline Excel.
The Receiver contains all of the electronics necessary to amplify, condition and process the
signals received by the infrared detectors. The advanced signal processing of Searchline Excel
employs two microprocessors.
One microprocessor, the Digital Signal Processor (DSP), is used to perform the necessary
intensive signal processing calculations.
The other microprocessor, the microcontroller, controls the overall function of the unit and
performs the final calculations to determine the correct gas reading and output state.
The primary output of the Receiver is a signal in the range 4 - 20mA and is available as either
source or sink options. For most applications, the output is calibrated for a range of 0 to 5
LEL.m. (See Appendix B for the explanation of LEL.m and other terms)
The Receiver also features an RS485 output which is used to communicate with the associated
SHC1 Handheld Interrogator. The SHC1 is used to perform final alignment, commissioning,
functional testing and diagnostic procedures.
The Receiver window is heated to minimise condensation, frosting and the buildup of snow.
The level of heating applied is controlled by the microcontroller and is adjusted from zero to
maximum depending on the window temperature.
Electrical connections to the Receiver are made via wires which run through the protective
flexible conduit. There are six Receiver wires, red (+24V), black (0V), white (4 - 20mA), orange
(RS485 A), blue (RS485 B) and green / yellow (GND).
2. OVERVIEW

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2.4 ADJUSTABLE MOUNTINGS
The adjustable mountings are:
•Purpose-built for Transmitter and Receiver.
•Robust.
•Rigid and stable.
•Made from stainless steel.
•Fully adjustable for alignment
Coarse and fine settings in both horizontal and vertical planes.
Adjustment range:
Vertical ±45o
Horizontal ±90o
Alignment details are given in Chapter 3.
Clamp nut
Mounting bracket
adjusting screw (2 off)
Adjustment clamp
lock screw (2 off)
Clamp nut
Pivot block
adjusting screw (2 off)
Adjustment clamp
lock screw (2 off)
2. OVERVIEW

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3.1 INTRODUCTION
Most of the information and recommendations given here only apply to the Open-Path version
of Searchline Excel. See Chapter 4 for details about installing the Cross-Duct version of
Searchline Excel.
Searchline Excel has been designed, engineered and customer tested to be the most robust,
reliable Open-Path Gas Detector (OPGD) available to date.
The design and technology employed in Searchline Excel makes it far more resistant to the
adverse effects of the operating environment and non-ideal installation engineering than previous
generations of OPGDs.
With careful consideration of the intended operating environment and the installation design,
the installer/operator can maximise the reliability, availability and performance achieved with
Searchline Excel.
Before designing or specifying an installation for Searchline Excel, it is strongly recommended
that the installation design authority reads all of this chapter and considers how the information
and recommendations provided can be applied to their installation(s).
If you have any queries concerning your installation design, contact Zellweger Analytics or your
local agents.
Zellweger Analytics is committed to ensuring that customers achieve reliable operation of their
Searchline Excel Gas Detectors. For this reason, Searchline Excel should only be installed by
fully trained personnel (trained by Zellweger Analytics or a Zellweger Analytics authorised trainer).
This training will provide the installer with a clear understanding of the Searchline Excel product
and the associated accessories and tools. It will also provide familiarity with the installation,
alignment and commissioning procedures, plus installation assessment skills to identify potential
problem areas.
For each installation, an installation check sheet should be completed and returned to ZA or
their agents. Details of this check sheet are given at the end of this chapter.
NOTE: THE INFRARED BEAM IS INVISIBLE AND EYE SAFE.
3. INSTALLATION AND OPERATION

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3.2 SITING AND MOUNTING
3.2.1 General
When designing an installation for a Searchline Excel gas detector it is important to give
consideration to where it is to be located, what potential sources of problems may be encountered
in this location and how the unit is to be mounted and supported.
3.2.2 Location for Best Coverage
Guidance on the positioning of gas detectors to provide the best detection coverage is contained
in BS6959 and other national Codes of Practice. It is recommended that the installation designer
consults these Codes of Practice when determining where detectors are to be located. In general,
the following positions usually provide the best results:
•Below potential leak sources for gases that are heavier than air.
•Above potential leak sources for gases that are lighter than air.
•Near to leak sources, along the expected leak trajectory, taking account of the
prevailing wind direction and any other factors which will influence propagation
of the leak.
•Between possible leak sources and any potential sources of ignition.
Location to Maximise Reliability and Availability
Care in choosing the location of Excel detectors can contribute significantly to the overall reliability
and availability.
When locating units, attempt to avoid areas where they may be adversely affected by the
following:
Vibration - Angular vibration of the structure to which Excel units are attached should be kept
to less than +/- 0.5°. Where possible, avoid locations where high levels of vibration will be
directly induced into the mounting structure. If close proximity to significant sources of vibration
is unavoidable, take steps to reduce coupling of this vibration and maximise the rigidity of the
mounting structure.
Intense Heat - Excel is certified and specified for operation in environments up to
+65°C. If sources of intense heat (flarestacks, intense sunlight, etc.) are present, a
sunshade (Part No: 2104B2323) or similar shield should be fitted to the unit to protect it
from excessive heating.
Sources of Heavy Contamination - Avoid locations where high levels of contaminants will
persistently be blown onto the unit s windows. Potential sources of heavy contamination include
generator/turbine exhausts, flarestacks, drilling equipment, process vents/chimneys etc. If
sources of heavy contamination cannot be avoided, consider fitting extra shielding and/or
providing good access for more routine cleaning.
Snow and Ice in Ambients Below -20 ° C - The heated optics on Excel units will melt snow or
ice on the windows in ambient temperatures down to approximately -20°C.
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3. INSTALLATION AND OPERATION
Below this temperature, snow or ice blown onto the window will not be melted until the ambient
temperature rises. If long-term, outdoor operation in very cold climates is intended, it is
recommended that extra shielding/covers are employed to prevent snow/ice from being blown
onto the windows and building up.
Note: The heated optics have not been evaluated as part of the performance testing relating to
the FM approval and therefore are not considered part of the performance approval.
Deluge and Flooding - Searchline Excel is rated IP66/67 and as such will not be damaged by
occasional deluge or flooding. However, during such instances the unit will completely lose its
IR signal and will enter the BEAM-BLOCK/FAULT state. Also, when the deluge/flooding subsides,
there is the possibility that contaminants will be left on the windows. Therefore, it is recommended
that Excel units be located away from areas particularly prone to deluge or flooding.
Areas Prone to Subsidence and Settling - Where possible, it is recommended that Excel units
are not mounted on structures located where problems with subsidence, settling or thawing of
permafrost are known to cause significant movement. If such locations cannot be avoided, the
foundations of the mounting structure should be engineered to minimise any angular movements.
Areas Prone to Earthquakes - In locations prone to earthquakes, there is a chance that
during or after an earthquake, the units of an Excel gas detector will become misaligned with
respect to each other. Provided that the Excel units do not suffer from direct mechanical impact
damage during an earthquake, they should remain undamaged by such events. Anti-vibration
mounts are unlikely to be of any benefit and are not recommended. After an earthquake it is
recommended that Excel gas detectors are visited and their alignment be checked.
Accidental Impact - Locations where there is a significant likelihood of equipment, personnel
or moving objects accidentally knocking Excel units out of alignment should where possible be
avoided. If such locations cannot be avoided, measures including improved mechanical
protection and warning notices should be considered.
Intense Electromagnetic Fields - Searchline Excel complies with EN50082 (Industrial levels)
and as such is well protected from interference by electromagnetic fields. However, locations in
close proximity to radio/radar transmitters, heavy electrical plant and high voltage power cables
may experience field strengths in excess of those specified in EN50082. Where possible, such
locations should be avoided or units should be installed as far as possible from the source of
the electromagnetic field. Measures including additional screening, filtering and transient
suppression may also be of benefit in such locations.
3.2.3 Beam Path
The Transmitter and Receiver units windows should face each other across the area to be protected
and, depending on the range of the Transmitter in use, should be the following distance apart:
Excel Gas Detector type Path length between units
Short Range 5 - 40m (15 - 130ft)
Medium Range 40 - 120m (130 - 390ft)
Long Range 120 - 200m (390 - 650ft)

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The beam path and immediate surrounds should be kept free of obstructions that might hinder the free
movement of air in the protected area or block the infrared beam. A clear beam path of 20cm diameter or
greater is recommended. In particular, for optimum availability, avoid areas affected by the following.
a. Steam vents and plumes
b. Smoke stacks and chimneys
c. Walkways and personnel areas
d. Splash and spray, e.g. from moving equipment, cooling towers, etc.
e. Parking, loading, cranes, vehicle temporary stops, e.g. bus stops, road junctions, etc.
f. Vegetation, e.g. shrubs, bushes, branches, etc. - if currently clear, movement due to
weather and future growth or planting must be considered
Note: Where c. and d. cannot be avoided, consider indicating the beam by marking the walkway
or road with paint.
Unit cowl
Telescope
clearance arc
-radius more
than 30cm
Beam
clearance arc
-radius more
than 10cm
Notes:
1. In order to fit the alignment telescope, used during the alignment process, a clear
accessible arc of at least 30cm radius is required close to the unit’s cowling as shown.
2. A clear beam path of at least 10cm radius or greater is recommended.
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3.2.4 Supporting Structure
The Transmitter and Receiver units should be fixed to a stable supporting structure using the
mounting plates supplied.
Note: The maximum movement of the supporting structure under all anticipated operating
conditions must be ± 0.5o.
If either unit is to be free standing and not mounted to existing supports or structures, and the
height above the ground is no more than 3m, the supporting structure shown is recommended:
!5+/53(15
4/,5
+
+
75
5
500mm
minimum
500mm
minimum
Concrete
foundation
500mm
minimum
Up to
3m
150mm dia. steel pipe,
nominal 6mm wall thickness
Excel mounting
plate
U-bolts,
8mm dia.
166mm
centres
Note: The pipe can be filled with concrete to provide extra robustness if necessary.
3.2.5 Orientation
Searchline Excel is solar immune and therefore there is no need to take account of the sun s
movement when considering orientation.
When positioning the units do not install them with the optical axis at an angle greater than 45o
to the horizontal. This is to avoid dirt/water buildup on the windows.
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3. INSTALLATION AND OPERATION
3.3 ELECTRICAL CONNECTIONS
3.3.1 General
All ranges of Searchline Excel comply with the EMC requirements EN50081 and EN50082. In
order to maintain compliance with these standards it is essential that the electrical installation
of Excel is engineered correctly.
Electrical installation standards vary for different countries, companies and applications and it
is the responsibility of the installation design authority to determine the applicable standards
and ensure compliance with them. When designing electrical installations for Excel, Zellweger
Analytics recommend that the installation design authority considers the following:
a. The unit cases should not, if possible, be connected to electrically noisy (dirty) metalwork or
conductors. Preferably, the case (internally connected to the green/yellow GND wire) should be
connected to a low noise instrument (clean) earth. See also para e. below. In order to facilitate
electrical isolation of the Searchline Excel from a noisy earth an isolation kit is supplied. This kit
should be fitted as standard unless local regulations forbid this.
b. The entire length of the field cabling connected to each unit should be fully shielded. This should be
connected to a low noise (clean) earth.
c. The low noise instrument (clean) earth system should only be connected to safety earth (usually
dirty) at a single point on the entire site/installation. This connection should be made in such a
manner that it does not introduce noise onto the low noise instrument earth. Star earthing
arrangements minimise earth current crosstalk.
d. The shields of the field cabling should not be connected such that earth loops are produced, or in
a manner that will result in the shields carrying large currents from heavy plant or equipment.
e. Ideally, the field cable shield should be connected to the unit s green/yellow GND wire, providing a
single, continuous earth shield. This connection must not be allowed to complete an earth loop.
f. The earth bonding arrangement must ensure that the maximum peak voltage between the unit
case earth and any field cable conductor is less than 350V. Voltages in excess of this can cause
permanent damage to the unit s RFI protection filters.
g. The use of a single, screened cable for each gas detector ensures maximum screening and
minimum crosstalk. Cabling arrangements which use a single cable for connecting a number of
field devices compromise screening, increase the potential for crosstalk and prevent implementation
of true star earthing.
h. Any electrical interference induced onto the 4 - 20mA loop conductors by the installation must be
kept below the levels necessary to comply with the general requirements of EN50054. In practice,
this means that peak noise currents induced on the current loop should be no greater than ±
0.25mA
j. The 0V rail of the control card/control system is directly connected to one side of the 4 - 20mA
current sensing resistor. Electrical noise on this rail is therefore directly connected to the 4 - 20mA
input. In order to avoid additional noise being induced on the 0V rail, it should not be commoned
with the safety earth/ground, which frequently carries a high level of electrical noise.
k. All electrical equipment connected to the gas detector should comply with EN50081 and EN50082.

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3. INSTALLATION AND OPERATION
l. The 24V supply should be free from large transients and fluctuations.
m. The field cabling conductors should have sufficient cross sectional area to ensure that the minimum
supply voltage applied to the gas detector is 18V at a current of 420mA. This corresponds to a
maximum round loop impedance of 14 ohms for a nominal 24V system supply.
n. Receivers should not be installed in close proximity to the antennae of high powered
radio, radar and satellite communication equipment.
3.3.2 Receiver Connections via DVC100
3.3.3 Receiver Connections via DX100
>
+24V DC supply
4-20mA output
0V DC supply
Rx (0V)
Rx (SIG)
Rx (24V)
8
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Instrument (clean)
earth
Cable shield
Blue B
Orange A
TB1
TB2
Green/ GND
Yellow
Red +24V
White 4-20
Black 0V
DX100 Junction Box
Receiver
connections
Control cabinet
connections
Safety/protective
ground
The earth bonding arrangement must ensure that the maximum peak voltage between
the unit case earth and any field cable conductor is less than 350V. Voltages in excess
of this can cause permanent damage to the unit’s RFI protection filters.
I.S. Barrier ground (CSA)
Earth terminal