13
MAN3038-2
DISCOVERY PRODUCT GUIDE
8
Carbon Monoxide / Heat Multisensor Detector
8.1
Operating Principles:
The Discovery CO/Heat Multisensor Detector contains a CO
detection cell and a thermistor temperature sensor whose outputs
are combined to give the final analogue value. The way in which the
signals from the two sensors are combined depends on the
response mode selected. The CO/ Heat Multisensor detects the
presence of carbon monoxide or heat or a combination of both.
The Multisensor construction is similar to that of a CO detector but
uses a different lid in order to expose the thermistor to the
surrounding air.
The signals from the CO sensing cell and the thermistor are independent and represent the amount of CO or
the temperature present in the vicinity of the detector. When the detector is used in heat only mode (Mode 5)
it operates as an A1R rate-of-rise heat detector with a static threshold of 58ºC. Discovery CO/Heat
Multisensor detectors incorporate additional temperature information that is intended for use in signal
processing which is achieved in the same way as that of the Optical/Heat Multisensor.
Characteristics of Response Modes
Mode 1
has very high sensitivity to carbon monoxide combined with moderate sensitivity to heat. This gives
a high overall sensitivity to both smouldering and flaming fires.
Mode 2
is set to report the presence of carbon monoxide only.
Mode 3
has moderate sensitivity to carbon monoxide combined with moderate sensitivity to heat and is used
for general applications.
Mode 4
has lower than normal carbon monoxide sensitivity combined with moderate heat sensitivity making
it suitable to areas where a certain amount of carbon monoxide might be considered normal.
Mode 5
has no response at all to carbon monoxide and acts as a rate-of-rise heat detector.
Notes
1. If the Multisensor is to be used in mode 5 heat detector spacing & coverage should be applied.
Observe the recommendations of BS5839: Part 1 or other applicable code.
2. In situ testing of the multisensory detector should be carried out as for CO detectors in response
mode 2 and for heat detectors in response mode 5. Both CO and heat sensors must be tested in
modes 1, 3 and 4.
Mode
CO Sensitivity
(ppm)
Temperature Sensitivity
(relative)
Response
Type
Minimum time to
alarm (seconds)
1
42
>21°C Increase
Multisensor
20
2
45
Not set to heat response
Carbon Monoxide
30
3
52
>21°C Increase
Multisensor
20
4
57
>21°C Increase
Multisensor
20
5
No response
to CO
A1R*
Heat Rate of Rise;
Static limit of 58°C
15
* Response is A1R to EN54-5 with fixed upper threshold of 58°C
Table 4 – CO/Heat Multisensor Response Modes
