Halma Ampac Orbis IS ORB-OP-52027-APO User manual

Fire detection and evacuation solutions that save lives.
Orbis IS
Product Guide
MAN3041-1

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Contents
1 Introduction to Intrinsic Safety............................................................................................................ 3
2 Range of Products ............................................................................................................................... 5
3 Features of Orbis IS ............................................................................................................................. 5
4 Choosing a Detector: Q & A................................................................................................................. 6
5 Orbis IS Optical Smoke Detector.......................................................................................................... 9
5.1 Where to use optical smoke detectors.......................................................................................... 9
5.2 How does the Orbis IS optical detector work ................................................................................ 9
5.3 Enviornmental Performance:.......................................................................................................10
5.4 Classification ...............................................................................................................................10
5.5 Technical Data:............................................................................................................................10
6 Orbis IS Multisensor Smoke Detector.................................................................................................11
6.1 Where to use optical smoke detectors.........................................................................................11
6.2 How does the Orbis IS multisensor smoke detector work?...........................................................11
6.3 Enviornmental Performance:.......................................................................................................11
6.4 Technical Data:............................................................................................................................12
7 Orbis IS Heat Detector........................................................................................................................13
7.1 Where to use heat detectors: ......................................................................................................13
7.2 Choosing the correct class of heat detector? ...............................................................................13
7.3 How does Orbis IS heat detectors work?......................................................................................13
7.4 Environmental Performance:.......................................................................................................14
7.5 Technical Data:............................................................................................................................14
8 Orbis IS Base.......................................................................................................................................15
8.1 Installing Orbis IS:........................................................................................................................15
8.2 Fitting Orbis detector heads: .......................................................................................................17
8.3 Orbis LED Status Indication..........................................................................................................17
9 Orbis IS Adaptor .................................................................................................................................18
10 System Design ....................................................................................................................................18
10.1 Types of safety barrier.................................................................................................................18
10.2 Approved safety barriers .............................................................................................................19
10.3 Safety earth.................................................................................................................................20
11 Wiring and cable types.......................................................................................................................21
12 Maximum loading of IS circuit............................................................................................................23
13 Installation .........................................................................................................................................23
14 Remote LED connection .....................................................................................................................23
15 MiniDisc Remote Indicator.................................................................................................................23
16 Servicing.............................................................................................................................................24
17 Achnowledgement .............................................................................................................................24

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1Introduction to Intrinsic Safety
There are many places where an explosive mixture of air and gas or vapour is—or may be—present
continuously, intermittently or as a result of an accident. These are defined as hazardous areas by BS EN
60079, the code of practice for installation and maintenance of electrical apparatus in potentially explosive
atmospheres.
Hazardous areas are common in petroleum and chemical engineering plants and in factories processing and
storing gases, solvents, paints and other volatile substances.
Electrical equipment for use in these areas needs to be designed so that it cannot ignite an explosive
mixture, not only in normal operation but also in fault conditions. There are a number of methods available
to achieve this but one of the most common is intrinsic safety.
Orbis™IS is a range of conventional detectors which has been developed from the standard range of Orbis
smoke and heat detectors.
Orbis IS is a range with modern styling and a TimeSaver IS base. It is electrically compatible with Series 60
intrinsically safe conventional detectors.
Orbis IS is suitable for use in marine and offshore applications as well as in land-based systems and has
been tested and approved to the following standards:
European Standard EN54
Fire Detection and Fire Alarm Systems:
EN54–7: 2000
Optical smoke detector
EN54–7: 2000 & CEA 4021: 2003
Multisensor smoke detector
EN54–5: 2000
Heat detector
Electromagnetic Compatibility
EN61000-6-3
EN50130-4
ATEX-related standards:
BSEN60079–0:2004
IEC60079–0:2004
EN50020:2002 and EN/BSEN/IEC60079–26:2004
Marine type approval standards:
American Bureau of Shipping (ABS)
Rules for Building and Classing Steel Vessels 2006
Bureau Veritas (BV)
Rules for the Classification of Steel Ships 2005
Det Norske Veritas (DNV)
Standard for Certification No 2.4: 2004
Germanischer Lloyd (GL)
Rules for Classification and Construction 2003

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Lloyds Register (LR)
LR Type Approval System
Marine & Coastguard Agency (MCA)
Merchant Shipping (Marine Equipment) Regulations 1999
Detectors have been declared as being compliant with the essential requirements of the EMC Directive
98/336/EEC, the Construction Products Directive 89/106/EEC and the ATEX Directive 94/9/EC. Intrinsic
safety certificates for ATEX is Baseefa 06 ATEX 0007X and for IECEx IECEx BAS 06.0002X.

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2Range of Products
Orbis IS comprises an optical smoke detector, a multisensor smoke detector, heat detector classes A1R,
A1S, A2S, BR, BS, CR and CS and a standard electronics-free base
3Features of Orbis IS
Orbis IS incorporates entirely new designs, both mechanical and electronic. The aim has been to make
installation quicker, enhance the reliability of detection and reduce the incidence of false alarms.
Orbis IS features:
•Modern styling
•TimeSaver Base® designed for fast installation and cable termination
•Wide operating temperature range
•StartUp™for fast commissioning
•DustDefy™housing which limits ingress of dirt into detector
•New optical sensor for high reliability, reduced false alarm and insect related problems
•New multisensor smoke detector for detecting fast-burning fires
•Algorithms for transient rejection
•Chamber designed to inhibit dirt penetration and thus reduce false alarms
•Automatic drift compensation with DirtAlert® warning
•FasTest® which reduces the time taken to test detectors
•Optional flashing LED to indicate normal operation
•SensAlert® is a safety feature. In the unlikely event of incorrect detector operation a yellow LED
flashes once a second.

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4Choosing a Detector: Q & A
What types of detector are available in the Orbis IS range?
An optical detector, a multisensor smoke detector and seven classes of heat detector.
How can I tell the Orbis IS range from standard Orbis detectors?
Orbis IS detectors have a printed legend around the lid which identifies them and provides information as
to their classification. They must be used with a certified Orbis IS mounting base which also bears a printed
legend.
The Orbis IS range does not include an ionisation smoke detector. Why is this?
Ionisation detectors have been in use for many years as extremely reliable smoke detectors and standards
such as EN54 recommend both ionisation and optical detectors as good general purpose smoke detectors.
Ionisation detectors, however, use a tiny radioactive foil. Although they are entirely safe to use, ionisation
detectors are subject to strict regulations concerning transport, storage and disposal. Thus it is becoming
increasingly difficult to transport and hence use Ionisation detectors. Advances in optical technology mean
that optical or multisensor detectors can now be used where previously ionisation detectors would have
been fitted.
Should I use optical detectors to detect smoke in all applications?
As stated, optical detectors have long been recommended as good general purpose smoke detectors.
Laboratory tests have been carried out to compare the performance of optical detectors in the standard
test fires described in the European standard EN54–7: 2000. The results of these tests are given in Figure 1.
The graph shows the acceptable response in terms of smoke density which is given as ‘m’ on the y axis.
Detectors must respond before the end of test which is an ‘m’ value of 2. The performance of Orbis IS
detectors is given as a solid line which shows how evenly the optical detectors respond to the test fires. If
detectors respond too quickly (the lower shaded portion of the graph) they may be too sensitive and hence
likely to generate false alarms. If detectors respond too slowly (the upper shaded portion) they are in
danger of not changing to the alarm state before the end of test. An even response in the centre is the ideal
response.
When would I use a multisensor?
Multisensor smoke detectors have a heat sensing element which makes them more sensitive if a fire
develops heat as well as smoke. This speeds up the response of the detector in certain fires where heat is
generated rapidly, for instance in test fire TF5, which is an open, flaming liquid fire in which n-heptane is
burned.
Multisensor smoke detectors are recommended for open flaming fire risks. If there is any doubt as to
whether an optical detector or a multisensor smoke detector should be used it is wise to fit a multisensor
smoke detector.
Where would there be a need to install heat detectors?
Heat detectors could be used if it is not possible to use smoke detectors. This will be the case where normal
industrial processes produce substances which could be mistaken for smoke by a smoke detector, e.g. flour

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mills, textile mills or chemical stores. The type of substance encountered here would cause frequent false
alarms if smoke detectors were fitted, so a heat detector is used instead.
Figure 1 - Orbis Optical Detector Response to Test Fires
Figure 2 - Comparisons of Response between Orbis Optical & Multisensor
How are heat detectors classified?
EN54–5: 2000 classifies heat detectors according to the ambient temperature in which they will be working.
An additional classification may also be applied to heat detectors in that they may be tested as ‘static’
detectors (changing to alarm at a preset temperature) or ‘rate-of-rise’ (changing to alarm at a preset
increase of temperature).
All Orbis IS heat detectors are tested and classified as either static or rate-of-rise.

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So what is the best way to choose a heat detector?
To make things easier we have produced a flow chart to help you decide.
Figure 3 –Choosing a Heat Detector

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5Orbis IS Optical Smoke Detector
5.1 Where to use optical smoke detectors
Optical smoke detectors have always been recognised as good
detectors for general use. They are regarded as particularly suitable
for smouldering fires and escape routes.
The performance of Orbis IS optical detectors is good in black as
well as in white smoke. In this respect Orbis IS is different from
traditional optical smoke detectors which perform far better in
white smoke than in black. Orbis IS optical detectors are also
designed to reduce significantly the incidence of false alarms
through over-sensitivity to transient phenomena.
Item No
Part No
Description
201-0604
ORB-OP-52027-APO
Orbis I.S. Optical Smoke Detector
Orbis IS optical detectors are recommended for use as general purpose smoke detectors for early warning
of fire in most areas.
The sensing technology in the Orbis IS optical smoke detector is significantly different in design from
previous optical detectors. A full description is given in the section ‘How do Orbis optical smoke detectors
work?’ but the advantages of this system and its associated algorithms are:
•Improved sensitivity to black smoke
•Compensation for slow changes in sensitivity
•Extra confirmation of smoke before alarm signal given
The algorithms are used to verify signals from the sensing chamber, to filter out transients and to decide
when the detector should change to the alarm state. All this combines to increase detection reliability and
reduce false alarms.
5.2 How does the Orbis IS optical detector work
The Orbis Optical IS smoke detector operates on the well established light scatter principle. The remarkable
optical design of the Orbis IS optical smoke detector allows it to respond to a wide spectrum of fires.
The sensing chamber of the Orbis IS optical smoke detector contains an optical sensor which measures
back-scattered light as well as the more usual forward scattered light. Sensitivity to black smoke is greatly
improved. The detector is calibrated so that it is highly reliable in detecting fires but is much less likely to
generate false alarms than ionisation smoke detectors.
The stability of the detector–high reliability, low false alarm rate–is further increased by the use of
algorithms to decide when the detector should change to the alarm state. This removes the likelihood of a
detector producing an alarm as a result of smoke from smoking materials or from another non-fire source.
The sensing chamber has been designed to keep out dust and other airborne contaminants.

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5.3 Enviornmental Performance:
The operating temperature for intrinsically safe detectors is restricted by the gas temperature class. See
technical data for full details.
5.4 Classification
II 1G Ex ia IIC –40°C<Ta<+40°C(T5)
–40°C<Ta<+60°C(T4)
BASEEFA Certificate Number
ATEX - Baseefa 06 ATEX 0007X
IECEx - IECEx BAS 06.0002X
5.5 Technical Data:
Specifications are typical and given at 23°C and 50% relative humidity unless specified otherwise.
Detector operating
principle:
Photo electric detection of light scattered by smoke particles over a wide range
of angles. The optical management comprises an infra-red emitter with a prism
and photo-diode at 90° to the light beam with a wide field of view. The
detectors microprocessor uses algorithms to process the sensor reading.
Sampling frequency:
Once every 4 seconds
Supply voltage:
14-28V dc
Supply wiring:
2 wires, polarity sensitive
Polarity reversal:
Not allowed
Power-up time:
<20 seconds
Minimum detector
active voltage:
12V dc
Switch-on surge current:
105µA at 24V dc
Quiescent current:
85µA at 24V dc
Alarm load:
325Ωin series with 1.0V drop
Material:
Detector and base moulded in white polycarbonate
Alarm Indicator:
Integral indicator with 360° visibility
Dimensions and weight
of detector:
100mm diameter x 42mm H
75g
Dimensions and weight
inc base:
100mm diameter x 50mm H
135g
Operating and storage
temperature:
-40°C to +70°C
Operating temperature is restricted by the intrinsic safety gas classification.
Class T5: - 40°C to +40°C Class T4: - 40°C to +60°C
The detector must be protected from conditions of condensation or icing.
Humidity:
0% to 98% relative humidity (no condensation)
Wind speed:
Unaffected by wind
Atmospheric pressure:
Insensitive to pressure
IP rating:
23D to EN60529:1992*
Electromagnetic
compatibility:
The detector meets the requirements of BS EN61000-6-3 for emissions and BS
EN50 130-4 for susceptibility.
* The IP rating is not a requirement of EN54-7: 2000 since smoke detectors have to be open in order to
function. An IP rating is therefore not as significant as with other electrical products.

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6Orbis IS Multisensor Smoke Detector
The multisensor smoke detector is a thermally enhanced smoke
detector and as such will not give an alarm from heat alone. It is a
development of the Orbis IS optical detector described in the
previous chapter and goes further in its capabilities of fire
detection.
6.1 Where to use optical smoke detectors
Multisensor smoke detectors are recognised as good detectors for
general use but are additionally more sensitive to fast burning,
flaming fires–including liquid fires–than optical detectors.
Item No
Part No
Description
201-0605
ORB-OH-53027-APO
Orbis I.S. Multisensor Detector
They can be readily used instead of optical smoke detectors but should be used as the detector of choice
for areas where the fire risk is likely to include heat at an early stage in the development of the fire.
As with Orbis IS optical smoke detectors the increased reliability of detection is combined with high
immunity to false alarms.
6.2 How does the Orbis IS multisensor smoke detector work?
The optical sensor is identical to the one in the Orbis IS optical detector. Its sensitivity is, however,
influenced by a heat sensing element which makes the detector more responsive to fast-burning, flaming
fires.
It should be noted that the detector is a smoke detector. Although the Orbis IS multisensory relies on both
smoke and heat sensors it is not possible to switch from smoke detection to heat detection.
6.3 Enviornmental Performance:
The environmental performance of the multisensory detector is the same as that of the Orbis IS optical
smoke detector.
Also classification and BASEEFA certificate number are the same as for the optical smoke detector.

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6.4 Technical Data:
Specifications are typical and given at 23°C and 50% relative humidity unless specified otherwise.
Detector operating
principle:
Photo electric detection of light scattered by smoke particles over a wide range
of angles. The optical management comprises an infra-red emitter with a prism
and photo-diode at 90° to the light beam with a wide field of view. The
detectors microprocessor uses algorithms to process the sensor reading.
The heat sensing element increase the sensitivity of the detector as the
temperature rises.
Sampling frequency:
Once every 4 seconds
Supply voltage:
14-28V dc
Supply wiring:
2 wires, polarity sensitive
Polarity reversal:
Not allowed
Power-up time:
<20 seconds
Minimum detector
active voltage:
12V dc
Switch-on surge current:
105µA at 24V dc
Quiescent current:
85µA at 24V dc
Alarm load:
325Ωin series with 1.0V drop
Material:
Detector and base moulded in white polycarbonate
Alarm Indicator:
Integral indicator with 360° visibility
Dimensions and weight
of detector:
100mm diameter x 50mm H
80g
Dimensions and weight
inc base:
100mm diameter x 60mm H
140g
Operating and storage
temperature:
-40°C to +70°C
Operating temperature is restricted by the intrinsic safety gas classification.
Class T5: - 40°C to +40°C Class T4: - 40°C to +60°C
The detector must be protected from conditions of condensation or icing.
Humidity:
0% to 98% relative humidity (no condensation)
Wind speed:
Unaffected by wind
Atmospheric pressure:
Insensitive to pressure
IP rating:
23D to EN60529:1992*
Electromagnetic
compatibility:
The detector meets the requirements of BS EN61000-6-3 for emissions and BS
EN50 130-4 for susceptibility.
* The IP rating is not a requirement of EN54-7: 2000 since smoke detectors have to be open in order to
function. An IP rating is therefore not as significant as with other electrical products.

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7Orbis IS Heat Detector
The Orbis IS range incorporates seven heat detector classes to suit
a wide variety of operating conditions in which smoke detectors
are unsuitable.
The European standard EN54-5:2000 classifies heat detectors
according to the highest ambient temperature in which they can
safely be used without risk of false alarm. The classes are identified
by the letters A to G. (Class A is subdivided into A1 and A2.) In
addition to the basic classification, detectors may be identified by a
suffix to show that they are rate-of-rise (suffix R) or fixed temperature (suffix S) types.
Item No
Part No
Description
201-0134
ORB-HT-51145-APO
Orbis I.S. A1R Heat Detector Rate of Rise
201-0135
ORB-HT-51157-APO
Orbis I.S. A1S Heat Detector Static
201-0601
ORB-HT-51147-APO
Orbis I.S. A2S Heat Detector Static
201-0600
ORB-HT-51149-APO
Orbis I.S. BR Heat Detector Rate of Rise
201-0607
ORB-HT-51151-APO
Orbis I.S. BS Heat Detector Static
201-0602
ORB-HT-51153-APO
Orbis I.S. CR Heat Detector Rate of Rise
201-0603
ORB-HT-51155-APO
Orbis I.S. CS Heat Detector Static
All heat detectors in the Orbis IS range are tested as static or rate-of-rise detectors and are classified as
A1R, A1S, A2S, BR, BS, CR and CS.
7.1 Where to use heat detectors:
Heat detectors are used in applications where smoke detectors are unsuitable. Smoke detectors are used
wherever possible since smoke detection provides earlier warning of fire than heat detection. There are,
however, limits to the application of smoke detectors and these are described in the section 4 ‘Choosing a
detector’. Heat detectors may be used if there is a danger of nuisance alarms from smoke detectors.
7.2 Choosing the correct class of heat detector?
Heat detectors have a wide range of response characteristics and the choice of the right type for a
particular application may not always seem straightforward. It is helpful to understand the way that heat
detectors are classified as explained earlier and to memorise a simple rule: use the most sensitive heat
detector available consistent with avoiding false alarms.
In the case of heat detectors it may be necessary to take a heuristic approach, i.e. trial and error, until the
best solution for a particular site has been found. The flowchart in section 4 will assist in choosing the right
class of heat detector. If the fire detection system is being designed to comply with BS 5839–1: 2002 heat
detectors should be installed at heights of less than 12 metres with the exception of class A1 detectors,
which can be installed at heights up to 13.5 metres.
7.3 How does Orbis IS heat detectors work?
Orbis IS heat detectors have an open-web casing which allows air to flow freely across a thermistor which
measures the air temperature every 2 seconds. A microprocessor stores the temperatures and compares
them with pre-set values to determine whether a fixed upper limit–the alarm level–has been reached. In

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the case of rate-of-rise detectors the microprocessor uses algorithms to determine how fast the
temperature is increasing.
Static heat detectors respond only when a fixed temperature has been reached. Rate-of-rise detectors have
a fixed upper limit but they also measure the rate of increase in temperature. A fire might thus be detected
at an earlier stage than with a static detector so that a rate-of-rise detector is to be preferred to a static
heat detector unless sharp increases of heat are part of the normal environment in the area protected by
the heat detector.
7.4 Environmental Performance:
The environmental performance is similar to that of the Orbis IS optical smoke detector but it should be
noted that heat detectors are designed to work at particular ambient temperatures (see Fig 3). Also
classification and BASEEFA certificate number are the same as for the optical smoke detector.
7.5 Technical Data:
Specifications are typical and given at 23°C and 50% relative humidity unless specified otherwise.
Detector operating
principle:
Measurement of heat by means of a thermistor
Sampling frequency:
Once every 2 seconds
Supply voltage:
14-28V dc
Supply wiring:
2 wires, polarity sensitive
Polarity reversal:
Not allowed
Power-up time:
<20 seconds
Minimum detector
active voltage:
12V dc
Switch-on surge current:
105µA at 24V dc
Quiescent current:
80µA at 24V dc
Alarm load:
325Ωin series with 1.0V drop
Material:
Detector and base moulded in white polycarbonate
Alarm Indicator:
Integral indicator with 360° visibility
Dimensions and weight
of detector:
100mm diameter x 42mm H
70g
Dimensions and weight
inc base:
100mm diameter x 50mm H
140g
Operating and storage
temperature:
-40°C to +70°C
Operating temperature is restricted by the intrinsic safety gas classification.
Class T5: - 40°C to +40°C Class T4: - 40°C to +60°C
The detector must be protected from conditions of condensation or icing.
Humidity:
0% to 98% relative humidity (no condensation)
Wind speed:
Unaffected by wind
Atmospheric pressure:
Insensitive to pressure
IP rating:
23D to EN60529:1992*
Electromagnetic
compatibility:
The detector meets the requirements of BS EN61000-6-3 for emissions and BS
EN50 130-4 for susceptibility.

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8Orbis IS Base
8.1 Installing Orbis IS:
Orbis IS has been designed to make installation fast and simple.
Figure 4 shows the TimeSaver Base as it is seen from the installer’s
point of view. The E-Z fit fixing holes are shaped to allow a simple
three-step mounting procedure:
•Fit two screws to the mounting box or surface
•Place the Orbis IS base over the screws and slide home
•Tighten the screws
The base offers three fixing centres at 51, 60 and 72mm.
A guide on the base interior indicates the length of cable to be stripped. Five terminals are provided for the
cables, four being grouped together for ease of termination.
The terminals are:
•positive IN
•positive OUT
•negative IN and OUT (common terminal)
•remote LED negative connection
•functional earth (screen)
The terminal screws are captive screws and will not fall out of the terminals. The base is supplied with the
screws unscrewed in order to avoid unnecessary work for the installer.
The end-of-line resistor should be connected between the OUT+ and COM–terminals. If it is required that
all detectors be fitted with their LEDs facing the same direction the bases must be fitted to the ceiling
observing the marking on the exterior which indicates the position of the LED.
The bases may be connected as shown in Figure 5 where remote LEDs, if required, are connected to the
associated base.
Figure 6 shows how to connect one remote LED to more than one base so that an alarm in any of the
detectors connected will switch the remote LED.

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Figure 4 –TimeSaver IS Base
Figure 5 –Orbis IS TimeSaver Base Wiring Diagram
Note: the earth in the base is provided for convenience where continuity of a cable sheath or similar is
provided. It is not necessary for the correct operation of the detector nor is it provided as a termination
point for a safety earth. If screened cable is used screen continuity should be maintained and the screen
should be earthed only at one point. The earthing point should preferably be close to the barrier. The
system complies with the requirements of the CPD only if wired using screened cable.

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Figure 6 –Orbis IS TimeSaver Base with Common Base LED Indicator
8.2 Fitting Orbis detector heads:
When the bases have been installed and the system wiring tested, the detector circuits can be populated.
Two methods are suggested:
1. Apply power and fit the detectors one by one, starting at the base nearest the panel and working
towards the end of the circuit. As each detector is powered up it will enter ‘StartUp’ and flash red,
refer Table 1 below. If the LED does not flash, check the wiring polarity on the base and ensure
there is power across IN+ and COM–. If the LED is flashing yellow the detector is not operating
correctly and may require maintenance or replacing, refer DirtAlert and SensAlert® section.
2. Fit all detectors to the circuit, apply power and check detectors by observing the LED status of each
device. The StartUp feature lasts for 4 minutes so it may be necessary to reset or de-power the
circuit to allow all detectors to be observed. The LED status is the same as method 1 above.
8.3 Orbis LED Status Indication
Feature
Description of Feature
Red LED Status
Yellow LED Status
StartUp
Confirms that the detectors are wired in
the correct polarity
Flashes once per
second
No Flash
FasTest
Maintenance procedure, takes just 4
seconds to functionally test and confirm
detectors are functioning correctly
Flashes once per
second
No Flash
DirtAlert
Shows that the drift compensation limit
has been reached
No Flash
Flashes once per
second in StartUp
(Stops flashing when
StartUp finishes)
SenseAlert
Indicates that the sensor is not operating
correctly
No Flash
Flashes every 4
seconds (Flashes
once per second in
StartUp)
Normal
Operation
At the end of StartUp and FasTest (without
flashing LED as standard)
No Flash
No Flash
Flashing LED
Version
Detectors red LED flashes in normal
operation (at the end of FasTest)
Flashes every 4
seconds
No Flash
Table 1 –Orbis Status LED Features

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9Orbis IS Adaptor
An adaptor is available which enables Orbis detector heads to be fitted to existing Series 60 IS bases in
order to upgrade systems with minimal disruption.
The existing system should conform to ATEX Certificate No. Ex97D2054 SYST. The IS Adaptor is
distinguished by the markings “part of intrinsically safe fire detector Baseefa06ATEX0007X”.
10 System Design
The design of an intrinsically safe fire detection system should only be undertaken by engineers familiar
with codes of practice for detection systems and hazardous area electrical systems. The relevant standards
are BS5839: Part 1, BS EN 60079-14:2003 respectively.
The fire detection performance of the Orbis I.S. range is the same as that of its standard counterparts but
some electrical parameters are different. Please use the technical data given in this guide for Orbis IS
devices. Performance information given in the Orbis Product Guide is applicable to the Orbis I.S. range.
The BASEEFA certification of the I.S. devices covers their characteristics as components of an intrinsically
safe system and indicates that they can be used with a margin of safety in such systems.
10.1 Types of safety barrier
The certified system configurations allow for two types of safety barrier, each of which has its own
advantages and disadvantages. A brief outline of their characteristics is given below.
Single Channel 28V/300Ω Barrier
This is the most basic type of barrier and therefore the lowest in cost. Being passive devices, they also
impose the minimum of restrictions on the operation of the fire detectors. Thus, single channel barriers are
available either as positive or negative polarity where the polarity refers to the polarity of the applied
voltage relative to earth. The significance of this is that one side of the barrier must be connected to a high-
integrity (safety) earth. Although this earth connection has no effect on the operation of Orbis IS devices
and is not needed for their correct operation, it may not be acceptable to the operation of the control and
indicating equipment. If the earth connection is not acceptable then the isolating barriers should be used.
Galvanically Isolated Barrier
Galvanically isolated barriers. These are also referred to as “transformer isolated d.c. repeaters”, “isolating
interfaces” and “transformer isolated current repeaters”. They differ from conventional shunt zener
barriers in that they provide electrical isolation between the input (safe area) and the output (hazardous
area). This is achieved by the use of a D.C./D.C. converter on the input side which is connected to the
hazardous area through a voltage and power-limiting resistor/ zener combination similar to a conventional
barrier.
The galvanic isolation technique means that the circuit does not need a high integrity (safety) earth and
that the intrinsically safe circuit is fully floating. Earth leakage problems for control and indicating
equipment are therefore eliminated if this type of interface is used.
Note: Although the circuit does not require a high integrity earth, it is permissible to earth either side of the
hazardous area circuit if required by other system considerations.

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Galvanically isolated barriers are available as single or dual channel versions and are recommended for any
application in which direct earth connections are not acceptable. Table 3 shows details of available barriers.
The galvanically isolated barrier is a two-wire device which does not need an external power supply.
10.2 Approved safety barriers
The system certification includes a generic specification for barriers.
The generic specification is:
any shunt zener diode safety barrier certified by BASEEFA or any EEC approved certification body to
[Ex ia] IIC
having the following or lower output parameters:
Uz = 28V
I max:out = 93.3mA
W max:out = 0.67W
In any safety barrier used the output current must be limited by a resistor ‘R’ such that
I max:out = Uz
R
A number of shunt zener diode barriers meet this specification and examples are given below:
Manufacturer
Type
Polarity
Mounting
Pepperl & Fuchs
Z 728
+ve
DIN –rail
Pepperl & Fuchs
Z 828
-ve
DIN –rail
Pepperl & Fuchs
Z 428/Ex
+ve
DIN –rail/surface
Pepperl & Fuchs
Z 528/Ex
-ve
DIN –rail/surface
MTL
MTL728+
+ve
Busbar
MTL
MTL7028+
+ve
DIN –rail
MTL
MTL7128+
+ve
DIN –rail
Table 2 –28V300Ωsingle channel safety barriers
Suitable transformer isolated current repeaters (galvanic barriers) are shown in Table 3.
Manufacturer
Type see table on
AZ20984
No of Channels
Certificate
Pepperl & Fuchs
KFDO CS EX 1.51P
1
BAS00ATEX 7087
MTL
MTL 4061
2
Ex94C2040X
MTL
MTL 5061
2
Ex94C2040X
Table 3 –Transformer Isolated (galvanic) barriers

MAN3041-1
20
10.3 Safety earth
Shunt zener diode safety barriers must be connected to a high integrity earth by at least one and preferably
two copper cables, each of cross sectional area of 4mm2 or greater. The connection must be such that the
impedance from the connection point to the main power system earth is less than one ohm.
Intrinsically safe circuits in the hazardous area should be insulated from earth and must be capable of
withstanding a 500V RMS AC test voltage for at least one minute. When using armoured or copper
sheathed cables, the armour or sheath is normally isolated from the safe area busbar.