AquiTron AT-GU Installation & Operating Manual

1. AT-GU Installation Instructions
To open the standard sensor enclosure, turn the cable gland ½ turn anticlockwise to loosen the internal gland nut, depress the clip on
top of the enclosure and open. Reverse to close.
Power: 12-24V AC/DC, connect at positions 0V and +V at connector block CN1. For AC – Jumper A is on, D is off. (See diagram
1/2.) For DC – Jumper A is off, D is on. (Default Factory Setting is DC). Use 2 cores of a 4-core cable, low voltage alarm type, typically
7/0.2mm sq.
Output: You can select the V or mA analogue output at JP1 and JP3. (Default factory setting is mA.) Connect the other two cores
of the cable to terminal block CN2 positions 0V and V or I for voltage or current as per jumper selection. You can common the two
zeroes and use 3 core cable if preferred.
Connect 4-20mA at CN2 positions 0V and I
Connect voltage output at CN2 positions 0V and V.
Relay Set Point: P1 sets the trip point for the relay and sounder using the 0-5V scale (measure at test points 0V and REF1, 2.5V
would be equivalent to half the range – (500ppm on a scale of 0-1000ppm.) Default factory setting is 50% of the range.
Time Delay: A time delay for the operation of the relay and sounder can be selected using jumpers JP5 and JP6. Default factory
setting is zero.
Sounder: The sounder can be disabled using jumper JP2. Default factory setting is enabled.
There is a 5 minute power up delay to allow the sensor to stabilize. This can be cancelled by shorting the pads of SW1 or SW2 – the
switches are not fitted in this version.
2. Location Of Sensors
Sensors must be located within the appropriate wire lengths from the central control unit.
In all cases the sensor supplied is designed for maximum sensitivity to a particular gas.
However, in certain circumstances false alarms may be caused by the occasional presence of sufficiently high concentrations of other
gaseous impurities. If such a situation is likely to arise installers should check with our Technical Department so that sensor(s) of
suitable cross sensitivity can be supplied. Examples of situations where such abnormalities may arise include -

Plant room maintenance activity involving solvent or paint fumes or refrigerant leaks.

Plant rooms in fruit ripening/storage facilities because of accidental gas migration (bananas - ethylene, apples - carbon
dioxide)

Heavy localised exhaust fumes (carbon monoxide, dioxide) from engine driven forklifts in confined spaces or close to
sensors.
A response delay is built in to the system to minimise the possibilities of false alarms.
Machinery Rooms
There is NO ABSOLUTE RULE in determining the number of sensors and their location. However a number of simple guidelines will
help to make a decision. Sensors monitor a point as opposed to an area. If the gas leak does not reach the sensor then no alarm will
be raised. Therefore, it is extremely important to carefully select the sensor location. Also consider ease of access for maintenance.
The size and nature of the site will help to decide which method is the most appropriate to use. Locations requiring the most protection
in a machinery or plant room would be around compressors, pressurized storage vessels, refrigerant cylinders or storage rooms or
pipelines. Most vulnerable are valves, gauges, flanges, joints (brazed or mechanical), filling or draining connections etc.
Gas Sensing System
INSTALLATION & OPERATING MANUAL
AT-GU