Tyco MR601TEx Product Information

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MR601TEx INTRINSICALLY SAFE ENHANCED OPTICAL SMOKE DETECTOR
PRODUCT APPLICATION AND DESIGN INFORMATION
1. INTRODUCTION
The MR601TEx Intrinsically Safe High Performance Optical Smoke Detector forms part of the M600Ex series of plug in detectors for ceiling mounting. The detector plugs into the 5BEx 5” Universal IS Base and is intended for two-wire operation on the majority of the control equipment currently manufactured by the company. The Intrinsically Safe High Performance Optical detector is available in one sensitivity setting only.
2. INTRINSIC SAFETY
The detectors are for use in potentially explosive gas and dust atmospheres (zone 0 gas, zone 20 dust).
The detectors are designed to comply with EN/IEC 60079­0:2006, EN/IEC 60079-11:2007 and EN/IEC61241-11:2006 for Intrinsically Safe apparatus. They are certified:
ATEX code:
II 1 GD
Certificate: BAS01ATEX1134X
Gas/Dust code: Ex ia IIC T5
Ex iaD 20 T100°C
IECEx Certificate: IECEx BAS 07.0056X
These detectors are designed and manufactured to protect against other hazards as defined in paragraph 1.2.7 of Annex II of the ATEX Directive 94/9/EC.
2.1 DETECTOR USE
It is recommended that the detector is used in conjunction with a suitable isolator or shunt diode safety barrier in a certified Intrinsically Safe system, ie, System 620.
2.2 SPECIAL CONDITIONS OF SAFE USE
The apparatus has a plastic enclosure which constitutes a potential electrostatic hazard. The enclosure must be cleaned only with a damp cloth.
3. OPERATING PRINCIPLE
The MR601TEx operates by sensing the optical scatter from smoke particles generated in a fire. While the optical scatter detector can give good detection performance for the majority of fires, some fast burning fires produce little visible smoke and some produce very black smoke, neither of which are easily detected by the optical scatter detector. (Such fires are represented in EN54-7 by Polyurethane and Heptane type fires respectively). These fires do, however, produce high heat outputs with an associated rise in air temperature.
The detector has been designed to offer improved detection of such fires, by detecting the rapid rate-of-rise of air temperature and under these conditions, increasing the smoke detection sensitivity. This gives an earlier detection of such fires and a broader detection capability than a standard detector.
The MR601TEx detector has two sensing systems as follows:
An optical chamber with associated electronics
to measure the presence of smoke by light scatter.
A thermistor with its associated electronics to
detect the presence of hot air draughts or high temperatures.
Fig. 1 Optical System Schematic
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SMOKE
PATH
SAMPLING
VOLUME
FINS
Fig. 2 Measuring Chamber Showing Smoke Flow Path
3.1 OPTICAL SYSTEM
The MR601TEx detects visible particles produced in fires by using the light scattering properties of the particles. The detector uses the optical arrangement shown diagrammatically in Fig. 1.
The optical system consists of an infra-red emitter and receiver, with a lens in front of each, so arranged that their optical axes cross in the sampling volume. The emitter, with its lens, produces a narrow beam of light which is prevented from reaching the receiver by the baffles. When smoke is present in the sampling volume a proportion of the light is scattered, some of which reaches the receiver. For a given type of smoke, the light reaching the photodetector is proportional to the smoke density. The amplified output from the sensor can be used to activate an alarm circuit at a predetermined threshold.
FINS
REFERENCE
SENSING
Fig. 3 Thermal Measuring System
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STATUS LED
IR EMITTER
PHOTO DIODE SENSOR
AMPLIFIER
GAIN
TIMER/ OSCILLATOR
SYNCHRONOUS DETECTOR
COMPARATOR
REF
SENSING THERMISTOR
REFERENCE THERMISTOR
1
2
COMPARATOR
THRESHOLD
LED
OUTPUT SWITCH
COUNTER
LINE A IN
LINE A OUT
LINE B IN/OUT
BRIDGE
BASE
R
L1 L2
L
REMOTE LED
Fig. 4 Block Schematic of Detector
3.2 FEATURES OF MEASURING CHAMBER
The MR601TEx uses vertical chevrons to exclude ambient light.
Smoke incident on the detector is channelled into the detector by the outer cover fins (Fig. 2) and passes through the vertical chevrons. The smoke is deflected into the optical chamber and through the sampling volume before passing out the other side of the detector.
The emitter (Fig. 1) is a GaAlAs solid state type operating in the near infra-red (880nm peak), while the detector is a matched silicon photodiode. These devices, together with their associated lenses, are held in place by the chamber mouldings. The design of the optical system is such that the presence of small insects such as thrips, should not cause false alarms.
3.3 THERMAL MEASURING SYSTEM
Refer to Fig. 3.
This is designed to detect the presence of horizontally moving hot air draughts moving across the ceiling which occur in a fast burning fire.
The measuring system consists of two fast responding negative temperature thermistors. A sensing thermistor is located above the labyrinth under the cover in the airstream and will detect any sudden changes in the air temperature or draughts of hot air moving across the ceiling. The second thermistor is located out of the airflow within the smoke labyrinth and has a longer time constant and is used as a temperature reference to compare the sensing thermistor against. At a given temperature differential between the two thermistors, the comparator will switch and increase the gain of the amplifier, thereby increasing the sensitivity of the sensor. Fins located on the top of the labyrinth are designed to increase air turbulence and the efficiency of the sensing thermistor.
3.4 CIRCUIT OPERATIONS
A simplified block schematic of the detector is given in Fig. 4.
The emitter is subjected to a pulse stream only every 10s in order to reduce the quiescent current. The pulse signal received by the photodiode is fed to a high-gain amplifier. If smoke is present, the pulse signal received varies in proportion to the smoke density.
The amplifier output is fed via an integrator, the output of which is compared to a preset threshold level. Sophisticated synchronous detection techniques are used to reduce the effects of noise and spurious transients.
The gain of the front end amplifier is controlled by the thermistor bridge circuit. When the temperature differential between the two thermistors exceeds a certain value, the amplifier gain increases. Under these conditions the High Performance Optical detector is more sensitive to the presence of smoke and is said to be in ‘Enhanced Mode’.
When the detector is in the ‘Enhanced Mode’, the detector will only alarm if a smoke signal is present. The presence of rising temperature alone cannot cause an alarm.
If the signal amplitude exceeds a threshold level, then the emitter samples the smoke every two seconds. The sample period remains at two seconds if the signal is above the threshold. When the counter has counted three consecutive pulses above the threshold, the output stage is latched into the alarm condition. If however, the amplitude of the second or third pulse is below the threshold, then the pulse period reverts to 10 seconds and the counter resets. The switching of the output stage lights the alarm LED and provides drive for the remote LED indicator.
The critical front end of the circuit is run off a 12V regulator to make it independent of supply voltage.
The detector is polarity conscious.
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Fig. 5 Overall Dimensions of MR601TEx
43
109
3.5 WIRING
Loop cabling is connected to base terminals as follows:
L-VE
L1 +VE IN
L2 +VE OUT
R Remote LED Drive
4. MECHANICAL CONSTRUCTION
The major components of the detector are:
Body Assembly
Printed Circuit
Optical Chamber
Optical Chamber Cover
Thermistor
Light Pipe
Outer Cover
4.1 ASSEMBLY
The body assembly consists of a plastic moulding which has four embedded detector contacts which align with contacts in the 5BEx base. The moulding incorporates securing features to retain the detector in the base.
The PCB is soldered to the body contacts. These contacts act as a mechanical fixture during assembly and provide electrical contact between the contacts and the PCB. The PCB is then potted.
The chamber cover is clipped to the body over the optical chamber ensuring the thermistor protrudes through the cover. The light pipe is slotted into the chamber cover. Finally, the outer cover is clipped to the body.
4.2 TEST AND FINAL ASSEMBLY
The detectors are fully functionally tested and their sensitivities set in a smoke tunnel to ensure correct calibration. The sealing ring and labels are then fitted to complete detector assembly.
5. TECHNICAL SPECIFICATION
5.1 MECHANICAL
Dimensions
The dimensions of the MR601TEx detector are shown in Fig. 5.
Materials
Body and cover: FR110 ‘BAYBLEND’
Fire Resistant
Fig. 6 MR601TEx Enhanced Optical Smoke Detector
with 5BEx 5” Base
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0
5
10
15
20
25
30
35
0 2 4 6 8 10 12 14 16 18
Detector Voltage (V)
Detecor Current [mA]
Fig. 7 Alarm Load Presented to the Controller
Wei ght
Detector: 0.128kg
Detector + base: 0.174kg
5.2 ENVIRONMENTAL
Operating Temperature: -20oC to +70oC
(please see note below).
Storage Temperature: -25
o
C to +80oC
Note:
1) The operating temperatures quoted exceed the ATEX Certification limits.
2) Operation below 0
o
C is not recommended unless steps are taken to eliminate condensation and hence ice formation on the detector.
Relative Humidity: 95% non-condensing
Shock: ) Vibration: ) Impact: ) To EN54-7 Corrosion: )
5.3 ELECTROMAGNETIC COMPATIBILITY
The detector complies with the following:
Product family standard EN50130-4 in respect of Conducted Disturbances, Radiated Immunity, Electrostatic Discharge, Fast Transients and Slow High Energy
EN 61000-6-3 for Emissions
5.4 ELECTRICAL CHARACTERISTICS
The alarm load presented to the controller is shown in Fig. 7.
The following characteristics shown in Table 1 are taken at 25
o
C with a supply voltage of 20V unless otherwise
specified.
Intrinsic Safety Rating:
Maximum Voltage for safety (U
i
): 28V
Maximum Current for Safety (I
i
): 93mA
Maximum Power Input (P
i
): 650mW
Equivalent Inductance (L
i
): 0
Equivalent Capacitance (C
i
): 0
5.5 PERFORMANCE CHARACTERISTICS
The fundamental parameter used to define the sensitivity of an optical smoke detector is the level of smoke which will just produce an alarm under ‘ideal’ conditions. This parameter, known as the response threshold value, is normally measured in a smoke tunnel and is defined in terms of the obscuration produced by the smoke over a one metre path. The response threshold value is normally given in dB/m, (or % per m).
Characteristics Min. Typ. Max. Unit
Operating Voltage (d.c.) 16 20 28 V Average Quiescent Current 90 110 μA Switch-on-Surge 130 μA Stabilisation Time 60 sec Alarm Current See Fig. 6 mA Holding Voltage 5 V Holding Current 1 mA Reset Time 2 5 sec Remote LED Drive Remote LED via 3.4k
Table. 1 Electrical Characteristics
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Interpretation of response threshold value is somewhat complicated by the fact that the measurement is given in terms of obscuration, whereas the detector works by scattering from the smoke particles. The response threshold (m) value will therefore, depend on the colour of the smoke. Black smokes give less scattering than light smokes for given values of obscuration as shown in Fig. 8.
Sensitivities are invariably specified for ‘grey’ smokes as produced by typical smouldering fires. Values for the MR601TEx are given below.
5.5.1 RESPONSE TO RATE OF CHANGE OF TEMPERATURE
The detector will not be enhanced by slow rates of change of temperature, or by cold air draughts moving across the ceiling creating negative rates of change of temperature. The detector is designed to detect sudden horizontal draughts of hot air produced by fast burning fires. The enhancement switching point has been set to allow the detection of TF1 type fires.
Normal response threshold = 0.19 dB/m, 2.7%/m typical.
Enhanced mode threshold = 0.08 dB/m, 1.1%/m typical.
5.6 RESPONSE TO FIRE TESTS
The response of an optical scatter detector to a fire will depend to a large extent on the colour of the smoke produced in the fire. However, other factors such as the detector smoke entry characteristics, the development of the fire and the thermal lift produced by the fire are important. In order to evaluate the response under realistic conditions, detectors are subjected to test fires which cover a range of fire types. These tests are defined in EN54 Pt 7. The MR601TEx passes the following Fire Tests:
Fig. 8 Response Threshold vs Smoke Colour
Note: TF2 to TF5 are mandatory test fires required to
meet EN54 Pt 7.
The MR601TEx is designed to respond to the mandatory tests TF2 to TF5 as required by BS5445 Pt 7. The MR601TEx gives an earlier response to TF5 fires than the MR601 due to its thermal circuit detecting the heat generated by this test of fire and the MR601TEx being ‘enhanced’. For the same reason the MR601TEx will detect test fire TF1 (open wood cellulosic flaming fire) which is not normally detected by optical smoke detectors ­demonstrating the detectors broader detection capability.
The MR601TEx does not respond to TF6 liquid (methylated spirit) which although having a rapidly rising temperature, does not generate any optical scattering. This shows that the High Performance Optical detector will not respond to hot air draughts without the presence of smoke.
6. INSTALLATION RECOMMENDATIONS
It is not recommended that the MR601TEx be installed in areas where it is likely to be regularly enhanced, since in this condition the detector is extra sensitive and there is a possibility of unwanted alarms from low ambient smoke levels.
The MR601TEx is designed to become enhanced by detecting a rapid temperature rise (>10°C) in air moving horizontally across the ceiling. Siting sensors in positions where air is being blown through the detector should therefore, be particularly avoided, eg, close to ceiling ducts or ceiling mounted industrial heaters; or areas of forced ventilation, such as ducts and under floor voids of computer suites.
Also, not recommended are areas open to the outdoors, such as cargo handling bays, or areas where the detector may become contaminated.
The MR601TEx is not recommended for use in applications where a heater jacket is required.
The MR601TEx is primarily aimed at benign environments.
TF1 open cellulosic (wood-flaming)
TF2 smouldering pyrolysis
TF3 glowing smouldering (cotton)
TF4 open plastics (polyurethane foam)
TF5 liquid (n-heptane)
Table 2: Response to Fire Tests
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7. CPD INFORMATION
8. DETECTOR IDENTIFICATION
The detector is identified by the logo label, as shown in Fig. 9.
0832
Tyco Safety Products Dunhams Lane Letchworth SG6 1BE UK
0832-CPD-0248
MR601TEx
Application & Design 01B-04-D12 Installation Instructions 01B-04-I3 Service Instructions 01B-04-S2
06
EN 54-7: 2000 + A1: 2002
Conventional Intrinsically Safe high performance photoelectric smoke detector with heat enhancement for use in fire detection and alarm systems in buildings
tyco
Fig. 9 Detector identification
GREEN
9. ORDERING INFORMATION
MR601TEx Intrinsically Safe Enhanced Optical Smoke Detector: 516.054.011.Y
5BEx 5” Universal IS Base: 517.050.023
JM/jm
5
th
May 2010
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