The true duct smoke detector VSD 301 is able to detect smoke at a very early stage in the rough environment of a ventilation duct without giving false alarms.
The true duct smoke detector VSD 301 is an optical obscuration designed to function inside the ventilation duct.
The sensing part of the true duct smoke detector covers as much as possible of the duct.
An infrared beam is transmitting through the sensing tube in the duct and if smoke present the beam is obscured to some extent and an alarm signal is given.
The true duct smoke detector has an adjustable level of sensitivity that goes from 3 to 25% (0,1 to 0,9 db/m) obscurity for all different environments that can exist in a duct.
You may ask, how does the true duct smoke detector cope with dust?
It surely must affect this true duct smoke detector as well.
Dust is always present in the return air duct as is air velocity.
The air will inevitably bring dust and this will stick to the true duct smoke detector optical parts, however, the electronics constantly monitor the obscuration within the sensing tube.
The air brings along dust and particles that of course also catches of the duct smoke detector. Despite it manage to be dirty without making a false alarm and without loosing its sensitivity and as the level changes slowly over a long period of time (weeks or months).
The signal of the true duct smoke detector is adjusted to compensate for this build of dust, however, should the obscuration change rapidly (seconds) this is signalled as smoke and will cause an alarm after an initial delay to compensate for drops of water or dust that disturbed from duct wall etc.
The true duct smoke detector is constructed to be connected to all in market existing
Fire Alarm- and BMS-system, both digital and analogue, as standard there is two alarm output with an open switch for smoke alarm and one analogue 2-10 Vdc for an output service alarm.
The internal calibration of the true duct smoke detector is provided at an outgoing terminal in order that the level may be seen if connected, for example, to a BMS-system.
The true duct smoke detector analogue output status levels is 2-10 Vdc.
2 Vdc means sensor fault, 3-7 Vdc means normal operation,
7-9 Vdc means optics needs cleaning and 9.5 V dc means smoke alarm.
Normal maintenance staff without previous training can clean true duct smoke detector . If they can clean a pair of glasses they can clean the true duct smoke detector, it is the same technique. This provides a better economic solution for the Life Cycle Cost, LCC for the end user.
The true duct smoke detector VSD 301 has been developed from a proven design using modern devices to provide effective and reliable detection of smoke in ventilation systems.
Detection of smoke for true duct smoke detector VSD 301 is achieved by monitoring a carefully controlled infrared beam (IR-detection, obscuration) within a perforated tube which is inserted into the ductwork. This method senses smoke directly within the duct, eliminating the problems associated with conventional detectors mounted in sampling boxes.
Circuitry incorporated in the design of the true duct smoke detector controls the infrared beam continuously. This ensures that the true duct smoke detector response will remain constant throughout operation of the system.
External influences including background pollution, airborne dust and low level electrical interference frequently found in commercial and industrial applications,
a common source of problems with some other types of true duct smoke detectors, are selectively filtered by the electronics thereby providing the highest sensitivity to smoke combined with effective rejection of short term disturbances that would otherwise give a false alarm.
The true duct smoke detector is equipped with a reset botton outside the enclosure.
The true duct smoke detectors features variable sensitivity and an advanced signal damping circuit which can be bypassed for testing purposes.
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- Outputs
– Relay SPDT 1A@24Vdc, 120 Vac
– Analogue 2-10 Vdc
- Relay output for closing fan/damper motor
- Damped output or undamped output
- The analogue output signal 2-10 Vdc can transmit
smoke or service alarm (dirt level) to BEMS system - Manual reset or auto reset
- Power supply 24 Vac/dc
- Probe lenght 300 mm.
- The true duct smoke detector is simple to clean and does not need to be removed from the duct work when cleaning is required.
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- Analogue output status levels
< 2 Vdc = Sensor fault
< 3-7 Vdc = Normal operation
< 7-9 Vdc = Optics require cleaning
> 9,5 Vdc = Smoke alarm
