Orbis I.S. A1R Heat Detector

Product code: ORB-HT-51145-APO

ORB-HT-51145-APO - Orbis I.S. A1R Heat Detector
The Orbis IS Heat Detector monitors temperature by using a single thermistor network which provides a voltage output proportional to the external air temperature. The Orbis IS range incorporates seven heat detector classes to suit a wide range of operating conditions.
Full Details

Application Environments

Dusty environments

Hazardous areas

Offshore platforms


Small to medium buildings

Brand Information

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 EM 60079, the code of practice for installation and maintenance of electrical apparatus in potentiality 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 I.S. is a range of conventional detectors which has been developed from the standard range of Orbis smoke and heat detectors. Orbis I.S. is a range with modern styling and a TimeSaver I.S. base. It is electrically compatible with Apollo Series 60 intrinsically safe conventional detectors. Orbis I.S. is a demonstration of Apollo's commitment to the market for high quality conventional detectors for use in small to medium size installations. In developing this range Apollo has put ease of installation and reliability in daily operation at the forefront of considerations. Orbis I.S. is manufactured in Apollo's Factory near Portsmouth, England,


Orbis I.S. 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 temperature and compares them with per-set values to determine whether a fixed upper limit - the alarm limit - has been reached. In 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 then 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.


The Orbis I.S. 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 suffix to show that they are rate-of-rise (suffix R) or fixed temperature (suffix S) type. All heat detectors in the Orbis I.S. range are tested as static or Rate-of-rise detectors and are classified as A1R, A1S, A2S, BR, BS, CR and CS.

Environmental Characteristics

The environmental performance is similar to that of the Orbis I.S. optical smoke detector but it should be noted that heat detectors are designed to work at particular ambient temperatures. Also classification and BASEEFA certificate number are the same as for the optical smoke detector. Operating and storage temperature: –40°C to +70°C Operating temperature is restricted by the intrinsic safety gas classification. Class T5: –40°C to +45°C Class T4: –40°C to +60°C The detector must be protected from conditions of condensation or icing.

Additional Information 1

Wiring and cable types It is not permitted to connect more than one circuit in the hazardous area to any one safety barrier and that circuit may not be connected to any other electrical circuit. Both separate and twin cables may be used. A pair contained in a type 'A' or 'B' multicore cable (as defined in clause 12.2.2 of BS EN 600079-14:2008) may also be used, provided that the peak voltage of any circuit contained within the multicore does not exceed 60V. The capacitance and either the inductance to resistance (L/R) ratio of the hazardous area cables must not exceed the parameters specified in datasheet PP2479. The reason for this is that energy can be stored in a cable and it is necessary to use cable in which energy stored is insufficient to ignite an explosive atmosphere. To calculate the total capacitance or inductance for the length of cables in the hazardous area, refer to datasheet PP2479, which gives typical per kilometer capacitance and and inductance for commonly used cables. (Note: all Orbis I.S. devices have zero equivalent capacitance and inductance.) Maximum loading of I.S. circuit Because of the finite resistance of the safety barrier, there will be a limit to the current drain which can be tolerated before the voltages on the circuit fall outside the specified limits for Orbis I.S. devices. The system certification allows up to 250 Orbis I.S. detectors to be connected to a single barrier circuit with an end-of-line resistor or not less than 1.8Ω. However, it must be ensure that the voltage available at each detector is above at the minimum specified in the quiescent condition. It is also important to ensure that the alarm load is suitable for the control and indicating equipment. the system certification also allows the use of remote LED indicators. These may be connected to individual detectors or may use a connection common to two or more detectors.

Product Information

The Orbis IS Heat Detector monitors temperature by using a single thermistor network which provides a voltage output proportional to the external air temperature. The Orbis IS range incorporates seven heat detector classes to suit a wide range of operating conditions.

Key Features

Can be used for applications where smoke detectors are unsuitable Ideal for environments that are dirty or smoky under normal conditions Reduced incidences of false alarms Increased reliability of detection

Key Benefits

TimeSaver® Base Patented FasTest® enabling functional testing in four seconds DirtAlert® indicates limit of drift compensation Tolerates extreme operating conditions: -40°C to +70 °C False alarm reduction Flashing LED option

Additional Information 2

Installation It is important that the Orbis I.S. detectors be installed in such a way that all terminals and connections are protected to at least IP20 when the detector is in the base. Special care must be taken with the rear of the mounting base where live metal parts may be accessible. Flush mounting of the base on a flat surface will provide the required degree of protection. The conduit box available from Apollo, part no. 45681-204, is also acceptable for mounting I.S. bases. Apollo also supplz a range of deckhead mounting boxes. For more information, please refer to PP1089, bases and accessories brochure. Note that the earth terminal in the base is provided for convenience where continuity of a cable sheath or similar is required. It is not necessary for the correct operation of the detector nor is it provided as a termination point for a safety earth.

  • Dusty environments
  • Hazardous areas
  • Offshore platforms
  • Refineries
  • Small to medium buildings
Warranty10 year
Chamber typeChevron
Heat classificationA1R
Maximum power-up time<20 seconds
Quiescent current80μA
Quiescent current tested at24V dc
Sampling frequencyOnce every 2 seconds
PolarityL1 & L2 are polarity sensitive
Minimum 'detector active' voltage12V
Holding voltage (min)5V
Minimum voltage to light alarm LED6V
Alarm reset voltage<1V
Alarm reset time1s
Alarm load325Ω in series with a 1.0V drop
Humidity (min)0% RH
Humidity (max)98% RH
Humidity Noteno condensation or icing
Humidity0% to 98% (no condensation or icing)
IP rating ValueIP23D
Storage temperature (min)-40°C
Storage temperature (max)70°C
Storage temperature-40 to 70°C
  • BV
  • LR
  • KRS
  • IECEx
  • FG
  • DNV.GL
  • MED
  • CCS
  • VdS
  • CPR
Materials housingPolycarbonate
Product length42mm
Product diameter100mm
Detection principleTemperature sensitive resistance.
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