15
Morley-IAS
996-203-000-2, Rev. 02
3.4.5 Detection Loops
3.4.5.1
General Information
-
The control panel supports analogue detectors with a data transmission system. It provides power
and communicates with the initiating devices over a two-wire circuit. All signalling loops communicate
with the panel using a proprietary protocol. In some market regions the selection of protocol
manufacturer is not available. Refer to the
Product Market Variations Manual
for details.
-
The number of detection loops provided on each of the panels is as follows:
Model
No. of Loops
Enclosure Size
DXc1
1
Small
DXc2
2
Medium
DXc4
4
Medium
EN54-2: 13.7
Maximum of 512
sensors/ MCPs
per panel.
EN54
!
-
It is possible for up to 800 addressable input points to be
connected to the DXc4 Series panel.
-
To comply with EN54-2 requirements, a maximum of 512
sensors/ MCP’s (input points) only should be connected to
the control panel across all analogue detection loops. This
limit includes any conventional detectors/ call points connected
to the system via zone monitors.
-
The panel conforms with the requirements of EN54-2 for MCP
alarm input response time.
The detection circuit should be separated from other cable runs to minimize the risk
of external interference. Under extremely noisy conditions, twisted pair wire is
recommended to further reduce interference.
The Detection Loop Circuits are supervised and power limited.
3.4.5.2
Cable Requirements
-
Shielded cable must be used for all detection (SLC) circuits. It is important that the shield is always
terminated to a good earth connection at both ends of the loop – earthing connection points are provided
in the enclosure for this purpose. The shield should never be connected to any other earth point in the
building. Refer to
Appendix 1 Specifications
for guidance on recommended fire-rated cables.
-
The core size, length of wiring run and detection circuit loading will produce a voltage drop along the
length of the cable. To determine if the loop driver can fully support the planned loop configuration,
use the detector manufacturers’ calculations for voltage and capacitance.
ALWAYS check that conductors of appropriate diameter are used so that the voltage
at the detectors is within the detector manufacturer’s specification.
The maximum permitted impedance for the SLC Loop is 40 ohms. This must be
reduced if loop powered sounders are installed.
-
The following table lists the maximum recommended cable loop lengths for each detection loop
using the indicated cable conductor sizes. Wiring to external devices should follow the appropriate
manufacturer’s instructions.
EN54-2: 7.1.3
Maximum of 10
secs to respond
to MCP alarms.
EN54
3
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