Dräger Flame 5000 Instrucciones De Uso página 9

3.2.1 Detector electronics subassembly
The field wiring is accessed by removing the rear enclosure cover and all
terminations are accessible without the need to access the electronics module
mounted in the front portion of the enclosure.
3.2.2 Earthing and screening requirements
It is important to ensure that the system is correctly connected to earth.
Incorrect or poor earthing can adversely affect system operation and may result
in intermittent RS485 communications and poor video image quality.
CAUTION
The equipment must be properly earthed to protect against electrical shock and
to minimise electrical interference.
The system 0 V should be connected to a clean earth at only one point;
generally this should be at the panel power supply (or 0 V bus bar). Where PC
equipment is connected to the RS485 and video signals, care should be taken
to ensure that the PCs and panels power supply are at the same ground
potential. Even small differences in earth potentials can cause an earth fault
current to flow resulting in video corruption. Where this is not possible either the
PCs local supply should be isolated and the PCs connected to the 'system
clean earth', or alternatively, the video and RS485 signals should be isolated.
The Dräger twisted pair to BNC video converter and RS232 to RS485 converter
can be used as long as the maximum potential difference between each earth
does not exceed ±5 V, as identified in the following section.
In distributed systems with multiple DC-DC power supply units, all 0 V supplies
must be connected together to a common clean earth. Where this is not
possible each system can either be connected to a local clean earth as long as
the maximum potential difference between each earth does not exceed
+4 to -1 VDC, alternatively the video and RS485 signals can be galvanically
isolated from the central system. Where earth fault monitoring is used care
should be taken to ensure that the system 0 V to earth potential is not
exceeded.
The detector enclosure is to be connected to a local earth and the detector
cable screens (shields) should be cut back to the crotch and not terminated
within the detector. If the detector enclosure cannot be connected to a local
Instructions for use |
Dräger Flame 5000
earth, then care should be taken to ensure the cable armour braid provides a
suitable earth or that the enclosure earth stud (external) is separately connected
to a suitable earth point using a single core 4 mm
All detector cable screens should be connected to the local clean earth at the
control panel. The screens (and twisted pairs) should be maintained to within 1"
(25.4 mm) of the terminations at the detector, within all junction boxes and at
the control panel. Where unscreened cables are used for panel wiring, then all
cables must be suitably twisted into pairs and video cables should be
segregated from other signal sources.
3.2.3 Detector wiring terminals
The wiring terminals and configuration links are mounted in the rear section of
the enclosure and are accessible by removal of the rear cover from the
enclosure. The electronics and the field terminals are separated so that there is
no reason to remove the electronics in order to access the field terminals. This
is to prevent damage to the electronics when the unit is being connected to the
field cable.
The device is supplied in one of two options:
A As a unit that provides relay contacts for the alarm and fault circuits across
which alarm and end of line resistors are fitted. When the unit is
disconnected from the control system and polarity across power supply
terminals 1 and 2 is reversed, the output from terminals 3 and 4 switch to
the RS485 protocol; this allows a Dräger Engineer access to the detector
configuration from the local equipment room.
B As a unit that provides 4-20 mA output. When the unit is disconnected from
the control system and polarity across power supply terminals 1 and 2 is
reversed, the output from terminals 3 and 4 switch to the RS485 protocol;
this allows a Dräger Engineer access to the detector configuration from the
local equipment room.
This may then be used to access the software revision within the detector via
the 'get settings' menu.
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Installation
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(0.16 inches ) earth cable.
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