5
Installation instructions continued
Relay connection for external alarm
One solid state relay is accessible for connection via a terminal strip located beneath the units
lower cover, this terminal strip is clearly visible in fig 1 top of page, if you need to make a
connection simply knock out the cable entry cut out beneath the relay terminal strip, and fit a 20
mm cable gland the relay contacts carry no voltage and are isolated.
SRC Relay specification
The relay is an SCR not ideally suited for switching inductive loads; try to use resistive loads
where possible, such as lights, buzzers, sounders etc. Only AC loads can be switched by the
relay, the voltage is 12 VAC to 240 VAC, Max current is 2A, Minimum AC load is 60 Ma
One normally open connection is available; the relay is active when an alarm condition is
present.
Relay connection on PCB
1= 1 Com
1= 1 out NO
Powering for the first time
After connecting the power, the unit requires up to three minutes to stabilize
,
During this time the monitor alarm circuit is muted and the displayed reading is held low, this is a
normal and necessary part of installation, after a short time the reading should settle down close
to zero, any reading from -0.05 to + 0.05 is acceptable.
Note: It may take up to 24 hours for the reading to stabilize fully,
if the unit is
commissioned in an atmosphere containing the target or other gas of the same group a zero
reading will not be possible, it is therefore advisable to first connect the unit in a place with clean
air other than the units intended monitoring location. After a low reading is achieved move the
monitor to its intended location.
Mounting location
Before mounting the monitor, experiment with several different locations, this is to avoid
nuisance alarming, bear in mind a lot of gasses are heavy and tend to concentrate at lower
levels, if for example two chemicals are present within the monitoring area, site the monitor
well away from the second chemical, if the room is not adequately ventilated a below alarm
level will not be possible.
Avoid mounting the monitor above a source of heat, radiator heating vent etc, fast moving air is
not representative of the areas average gas value.
