Honeywell 705 Series User manual

Sensors Type 705
H2S Sensor and Transmitter for
Electrochemical Cells Ul Certified
Operating Instructions

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HELPING TO MAKE A SAFER WORLD
Ensure that you read and understand these operating
instructions BEFORE installing or operating any part of the
equipment.
Please pay particular attention to the Safety Warnings.
WARNINGS
1. To maintain safety standards, regular maintenance,
calibration and operation of this equipment by
qualified personnel is essential. Read and understand
this manual completely before operating or servicing.
If any further details are required which do not appear
in this manual contact Zellweger Analytics Limited or
their agent.
2. The Code of Practice regarding 'Selection, Installation
and Maintenance of Electrical Apparatus for use in
Potentially Explosive Atmospheres' must be complied
with at all times. Refer to the appropriate local or
national regulations relative to the installation site.
Elsewhere the appropriate local or national
regulations should be used.
3. Operators must be fully aware of the action to be
taken if the gas concentration exceeds an alarm
level.
CAUTION
To maintain safety standards, regular maintenance,
calibration and operation of the equipment by qualified
personnel is essential.

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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. If further details are required which do not appear in
this manual, contact Zellweger Analytics Limited or
one of their agents.
HELP US TO HELP YOU
HELPING TO MAKE A SAFER WORLD
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 the
contents of any of our documents and to this end we include
the form opposite for you to photocopy, complete and return
to us so that we may take the appropriate action.

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1. INTRODUCTION 7
1.1 General 7
1.2 Principle of Operation 8
1.3 Accessories 8
2. INSTALLATION 12
2.1 Unpacking 12
2.2 Sensor Orientation 12
2.3 Terminal Housings 12
2.4 Cable Connections 13
2.5 Fitting Sensors 14
3. FITTING ACCESSORIES 16
3.1 Collecting Cone 16
3.2 Weather Protection Housing 16
3.3 Sample Flow Housing 16
4. MAINTENANCE 18
4.1 General 18
4.2 Cleaning 18
5. CALIBRATION 19
5.1 General 19
5.2 Cross Interference From Other Gases 19
5.3 Sensor Life 19
5.4 Calibration Procedure 20
6. GASSING THE SENSOR 21
6.1 Equipment Required 21
6.2 Calibration Gassing Procedure 21
7. REPLACEMENT PARTS 23
7.1 Terminal Housings 23
7.2 Maintenance Spares 23
8. Type 705 Sensor Alternative Systems 24
9. SPECIFICATION 25
CONTENTS

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1.1 GENERAL
The 705 ECC Sensor (Figure 1) is a hydrogen sulphide toxic
gas detector certified for installation in a hazardous area.
This version uses an electrochemical sensor, in conjunction
with an electronic circuit to form a 2-wire 4 - 20mA transmitter.
The sensor comprises an aluminium housing containing an
electrochemical cell with a sintered stainless steel disc
forming the face of the sensor. The housing has a 47mm AF
body with a 3/4 NPT mounting thread at one end and an
M36 accessory thread on the other end. A plastic Filter
Housing screws on to the accessory thread that holds the
Hydrophobic Barrier in position, if accessories are not fitted.
There are a number of accessories available for the 705
Sensor which utilise the M36 accessory thread. Refer to
Section 8 for alternative systems to which the 705 Sensor
can be connected.
Note: New Sensors are despatched with a protection disc
in place of the Hydrophobic Barrier. This disc should
not be removed until the sensor is installed or
commissioned.
1. INTRODUCTION
Figure 1 Type 705 Sensor and Filter Housing
Mounting Thread
Accessory Thread
Sintered Disc
Hydrophobic Barrier
(fit white side out)
Filter Housing

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1.2 PRINCIPLE OF OPERATION
The sensor contains an Electrochemical Cell which generates
an electrical current in proportion to gas concentration within
the cell. Since the current output from the cell is in microamps,
this is amplified and processed by the electronics in the
terminal enclosure. The resulting signal, in the range 4 -
20mA and representing 0 - 50ppm H2S, can then be wired to
equipment in the safe area to provide alarm and concentration
indications.
1.3 ACCESSORIES
1.3.1 General
The following accessories are available for use with the
sensors:
a. Collecting Cone (Figure 2).
b. Weather Protection Housing (Figure 3).
c. Sample Flow Housing (Figure 4).
d. Hydrophobic Barrier.
e. Gassing Point Assembly (Figure 5).
1.3.2 Collecting Cone
The detection of a lighter than air gas is enhanced by the use
of a Collecting Cone. The cone fits onto the sensor accessory
thread in place of the Filter Housing and retains the
Hydrophobic Barrier.
A nozzle on the cone permits gassing of the sensor with the
cone in position. The test gas is applied either direct to the
nozzle or via a permanently connected pipeline when the
sensor is in an inaccessible location.
1. INTRODUCTION

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1.3.3 Weather Protection Housing
The Weather Protection Housing, fitted to a sensor installed
in an exposed location, affords protection from driving rain
from vertical to 30° below horizontal. When mounted close
to the ground, protection is afforded from heavy rain
rebounding off the ground. It also reduces contamination
from industrial waste and enables the application of test gas
in high wind speeds without significant error.
The housing is fitted to the sensor accessory thread in place
of the Filter Housing and retains the Hydrophobic Barrier.
Incorporated in the housing is a nozzle to facilitate gassing
of the sensor with the Weather Protection Housing in position,
either by direct application to the nozzle or via a permanently
connected pipeline. The nozzle is free to rotate within the
housing to allow removal from the sensor without
disconnecting a permanently connected pipeline, when
changing the Hydrophobic Barrier and cleaning the sensor.
1. INTRODUCTION
Figure 2 Collecting Cone
Nozzle 6.35 O/D
77.6mm
165mm
42mm

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1.3.4 Sample Flow Housing
A Sample Flow Housing provides a facility to allow sampling
of a closed system by means of two pipelines. The flow
housing is fitted to the sensor accessory thread by a locking
ring that enables the housing to be removed without
disconnecting the pipeline. The Hydrophobic Barrier is
retained by the housing and interfaces with a gasket bonded
to the housing.
1. INTRODUCTION
50.8mm Dia
25.5mm
51.0mm
Figure 3 Weather Protection Housing
Figure 4 Sample Flow Housing
61mm
45mm
31mm
30mm

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1. INTRODUCTION
1.3.5 Gassing Point Assembly
The Gassing Point Assembl assembly can be fixed in a
convenient position and permanently connected by suitable
tubing to an inaccessible sensor, thus simplifying the
application of test gas when checking sensor calibration. A
DIN Rail Mounting Assembly (00785-A-0069) is available to
enable five gassing point assemblies to be mounted side by
side.
1.3.6 Hydrophobic Barrier
The Hydrophobic Barrier consists of a layer of stainless
steel mesh with a rubber rim. A hydrophobic barrier of PTFE
is bonded to the stainless steel surface.
This MUST be fitted with the white surface faceing outwards.
Figure 5 Gassing Point Assembly
25mm
Gassing Tube Cap
Stainless Steel
Tube
120 mm Dia
Yellow Nylon Block
70mm x 38mm x 19mm

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WARNING
The Code of Practice regarding ‘Selection, Installation
and Maintenance of Electrical Apparatus for use in
Potentially Explosive Atmospheres’ must be complied
with at all times. Refer to the appropriate local or national
regulations relative to the installation site.
CAUTIONS
1. Replacement of components by other than Zellweger
Analytics authorised engineers will invalidate the
instrument warranty and certification.
2. The Type 705 Sensor must never be used in
conditions when the flameproof integrity of the sensor
and associated terminal housing is impaired.
3. The sintered disc on the sensor assembly must be
kept free from contaminants. ie. Oil and dirt.
2.1 UNPACKING
On receipt the equipment must be carefully unpacked,,
observing any instructions printed on the packaging, and the
contents checked for deficiencies and transit damage.
2.2 SENSOR ORIENTATION
The sensor must be installed with the Sensor facing
downwards. In exposed locations a Weather Protection
Housing should be fitted.
2.3 TERMINAL HOUSINGS
A Terminal Housing (Figure 6) provides a mounting base for
the sensor and contains the associated electronic circuit.
The installation wiring enters the Terminal Housing via
conduit.
2. INSTALLATION

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2. INSTALLATION
2.4 CABLE CONNECTIONS
The sensor is connected by three wires to the terminals on
the pcb:
Connections Colour Code
Counter C Brown
Working W Blue
Reference R White
Two 3-way terminals blocks on the pcb in the terminal
enclosure enable the sensor to be connected to equipment
in the safe area. For wiring details see Figure 7.
Cable Entry Conduit
Adalet X1HFC3L
Terminal Housing
Killark Box with
705 Sensor
Cable Entry Conduit
Figure 6 Terminal Housings

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2.5 FITTING SENSORS
WARNINGS
1. Before installing the sensors, isolate the power supply
by disconnecting or removing the associated control
module from the installation.
2. All electrochemical cells contain acid or caustic
solution; avoid contact with the skin, eyes and
clothing. In case of contact flush the area with water
for at least fifteen minutes.
CAUTION
The sintered disc on the sensor assembly must be kept
free from contaminants, for example oil and dirt.
2. INSTALLATION
RFI Shield Plate
Connection Terminals
Span
TP3
TP2
Zero
Offset
Figure 7 Circuit Board Assembly Connections
Controls and Connections

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When fitting a sensor to a metal thread, it is recommended
that the mounting thread should be coated with an approved
anti-seize compound, such as a light petroleum grease.
Refer to Section 8 for alternative systems to which the
sensor can be connected. If replacing a sensor refer to
CAUTION 1 in the Maintenance section.
To fit the 705 Sensor proceed as follows:
(1) Remove the protection disc and fit the accessories as
required. (Refer to Section 3).
(2) Isolate the power supply and wait for five minutes.
(3) Remove the Terminal Housing lid.
(4) Pass the cable into the Terminal Housing and fit the
sensor to housing. To comply with the certification
requirements, a minimum of five threads must be
engaged.
(5) Connect the sensor cable to the terminal block.
(6) After mounting the Terminal Housing in the required
location, connect the associated Control Module wiring
to the terminal block (see label).
(7) Fit the shield plate to the standoff pillars. Replace and
secure the Terminal Housing lid.
(8) If not already replaced by accessories, unscrew the
Filter Housing, remove the protection disc and replace
Filter Housing and gasket.
Note: The Hydrophobic Barrier is retained in position by
the Filter Housing, or one of the accessories.
(9) Reconnect to the Control Module.
2. INSTALLATION

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3.1 COLLECTING CONE (00780-A-0032)
To fit the Collecting Cone Assembly to a sensor, carry out
the following:
(1) Remove the Filter Housing and gasket from the sensor.
(2) Fit the Hydrophobic Barrier, ensuring that the white
surface faces away from the sinter.
(3) Screw the Collecting Cone assembly onto the sensor
accessory thread and tighten firmly by hand.
3.2 WEATHER PROTECTION HOUSING
(00780-A-2076)
To fit a Weather Protection Housing to a sensor carry out the
following:
(1) Remove the Filter Housing and gasket from the sensor.
(2) Fit the Hydrophobic Barrier, ensuring that the white
surface faces away from the sinter.
(3) Screw the Weather Protection Housing on to sensor
accessory thread and tighten firmly by hand.
3.3 SAMPLE FLOW HOUSING (00780-A-0035)
To fit a Sample Flow Housing to the sensor, carry out the
following:
(1) Remove the Filter Housing and gasket from the sensor.
(2) Ensure that the Sample Flow Housing is fitted with its
gasket (00780-C-0017).
(3) Apply a thin coating of anti-seize compound, such as a
light petroleum grease, to the sensor accessory thread.
3. FITTING ACCESSORIES

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(4) Fit the Hydrophobic Barrier, ensuring that the white
surface faces away from the sinter. Screw the Sample
Flow Housing on to the sensor and tighten with a
40mm A/F spanner.
(5) Set the sample flow rate to 1.5 ± 0.1 litres per minute,
unless otherwise directed in System installation
instructions.
3. FITTING ACCESSORIES

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4.1 GENERAL
Maintenance consists of cleaning the sensor and accessories,
replacing gasket and the Hydrophobic Barrier and gassing
the sensor when testing the system.
CAUTIONS
1. The ECC cell contains a small quantity of acid. It is
therefore necessary to comply with the current waste
disposal regulations, either local or national, when
disposing of a sensor.
ECC TYPE SENSORS SHOULD NEVER BE
DISPOSED OF BY PLACING IN A FIRE.
2. Exposure to concentrations above the design range
may result in the sensor needing re-calibrating or
checking.
3. Dismantling of a sensor or a sensor installation by
other than authorised engineers invalidates
certification.
In the event of exposure to contaminant or prolonged
exposure to high concentration of gas, the sensor should
be operated for 24 hours in a clean environment and
then recalibrated.
Note: If the sensor is found to be faulty, or cannot be
calibrated, the complete sensor must be discarded
and replaced.
4.2 CLEANING
Sensor and accessories may be cleaned using an industrial
grade of methanol. Whenever cleaning takes place, a new
Hydrophobic Barrier must be fitted and the following
precautions must be observed:
a. Isolate power supply from the sensor by withdrawing
the associated Control Module from the installation.
b. Do not remove sensor from the installation.
4. MAINTENANCE

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5.1 GENERAL
When testing and calibrating a gas detection system, the
sensors must be gassed in accordance with the practice
recommended for the particular installation. The sensor
should be calibrated with hydrogen sulphide using the
procedures detailed in Section 6.
5.2 CROSS INTERFERENCE FROM OTHER
GASES
Some gases other than hydrogen sulphide can produce an
output current. Those which may be encountered and typical
examples of their effect (if any) at 20ºC are as follows:
Gas Concentration Indication
in ppm H2S
Carbon Dioxide 25% 0
Carbon Monoxide 100ppm 0
Ethylene 500ppm 0
Hydrogen 100ppm 0
Methane 5% 1
Sulfur Dioxide 100ppm 0
5.3 SENSOR LIFE
The expected life of the detector assembly is greater than
two years. The guaranteed life is 12 months in use, plus six
months storage, subject to storage at a stable temperature
of between -10 to +20ºC. This guarantee will not apply to
extended use in harsh environments.
5. CALIBRATION

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5.4 CALIBRATION PROCEDURE
Note: This procedure will produce an upscale output signal
which may activate alarms if fitted. Refer to the
Warnings in Installation section of the manual before
proceeding.
(1) Allow a minimum warm-up period of 1 hour after
applying power before carrying out this procedure.
(2) Insert a Digital Multimeter (DMM), set to read current,
in series with the 4 - 20mA line.
(3) Ensure the sensor is in a gas-free atmosphere then, if
necessary, adjust the ZERO control for a reading of
4mA on the DMM.
(4) Gas the sensor as instructed in Section 6 'Gassing the
Sensor'. After 5 minutes, adjust the SPAN control for
a reading of 20mA on the DMM for 50ppm H2S.
(5) If procedures (3) and (4) cannot be achieved, adjust
the Offset control as follows:
a. Connect the DMM, (set to read mV), between
TP2 and TP3 on the pcb (see Figure 7).
b. Adjust the ZERO control to obtain 0.000V ± 1mV
on the DMM.
c. Disconnect the DMM.
d. Adjust the OFFSET control to obtain an output
(at terminals) of 4mA.
e. Repeat steps (3) and (4), remove the gas adaptor
and allow sufficient time for the test gas to
escape.
(6) Turn off the test gas and check that the DMM indicates
4mA. If not, adjust the ZERO control to give a DMM
reading of 4mA.
5. CALIBRATION

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6.1 EQUIPMENT REQUIRED
To test and calibrate the gas detection system, the following
items are required:
a. A suitable Calibration Gas Test Kit and a bottle of the
appropriate test gas.
b. Where the sensor accessories are not fitted, a Sample
Flow Housing will be required for accurate sensor
calibration.
Note: Purpose built gassing equipment is available on
request from Zellweger Analytics Limited.
6.2 CALIBRATION GASSING PROCEDURE
CAUTIONS
1. The calibration of H2S sensors requires extreme
care and accurate gas mixtures. Electrochemical
sensors are better left factory calibrated and only an
approximate calibration check made.
2. If applying H2S test gas via a gassing nozzle, such
as on the Weather Protection Housing, the control
system may indicate up to 20% high. This is normal
and the system does not need recalibrating.
3. Should recalibration of a H2S sensor be required, a
Sample Flow Housing should be used to ensure
accuracy.
To calibrate a H2S sensor, proceed as follows:
(1) Connect a suitable calibration gas test kit to the sensor
gassing nozzle or to the permanently connected
pipeline, if fitted.
6. GASSING THE SENSOR