GAS Gasmaster, Installation, Operation And Maintenance Manual

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8
Conventional fire detectors
A loop of up to 20 conventional smoke/heat detectors
(for example Apollo Series 65 or Orbis devices’) can
be connected to each Gasmaster input channel.
A fire loop can also comprise switched devices such as
manual alarm call points or flame detectors, and devices
can be mixed on the same loop provided electrical
characteristics are compatible and fire regulations allow.
Switched devices require a 470 Ω series resistor. Each fire
loop must be terminated with a 1K8 end-of-line resistor,
which is monitored to provide indication of open circuit
or short circuit faults. Connection details are shown in
section 2.8.3.
Environmental Sampling Unit (ESU)
Each Gasmaster input can monitor a Gas Alarm Systems
Environmental Sampling Unit (ESU), which enables
detection of flammable or toxic gases over a wide area
using a sample draw technique. It is essential that the
sampling device on the ESU is operating correctly, and
Gasmaster provides this monitoring function to ensure
a sample is being drawn. Gasmaster provides a 2-wire 24
V dc supply to the sampling device. Separate Gasmaster
input channels are required to monitor the gas detector
or detectors fitted to the ESU. Connection details are
shown in section 2.8.5.
mV bridge pellistor detectors
Some flammable gas detectors provide a mV bridge
type signal rather than a 4-20mA signal. Example Gas
Alarm Systems products are Xgard Type 3 and Xgard
Type 4. The procedure for setting-up these detectors is
different from 4-20mA devices: refer to section 2.12.1 for
detailed instructions on commissioning mV bridge type
detectors
Please contact Gas Alarm Systems for specific wiring
details for Gas Alarm Systems detectors
2.8.1. Two wire 4-20mA devices
Figure 2.6 shows a typical wiring configuration for a
2-wire current sink detector for safe area use only.
Figures 2.7 and 2.8 show typical wiring configurations
for I.S. detectors installed in hazardous areas using Zener
Barriers or Galvanic isolators. Refer also to section 1.3.
Set the link on the 4-20 mA/Fire input module to SINK
in all cases.
Figure 2.6 Connections for 2 wire detector 4-20mA/Fire
input module
Figures 2.7 and 2.8 show typical wiring configurations for
a 2 wire sink I.S.detector with Zener barrier or Galvanic
Isolator. Set the link for the appropriate channel as
shown in each diagram.
2.8.2. Three wire 4-20mA devices
Figure 2.9 shows a typical wiring configuration for a
3-wire detector. Set the link on the 4-20 mA/ Fire input
module to SOURCE for a current source detector, and
SINK for a detector configured as current sink.
Figure 2.9 Connections for 3 wire detector 4-20mA/Fire
input module
2.8.3. mV bridge pellistor detectors.
Detectors such as Gas Alarm Systems’s Xgard Type 3 or
4 should be connected as shown. Refer to section 2.12.1
for instructions on detector set-up.
Refer to Figure 5.1 on page 37 for wiring details.
Important: to avoid signal interference, it is essential
that detector cables do not lay over mV pellistor input
modules (hatched area on diagram).
2. Installation