13
WARNING
Prior to carrying out any work ensure local regulations and
site procedures are followed. Never attempt to open the
detector or junction box when flammable gas is present.
Ensure that the associated control panel is inhibited so as to
prevent false alarms.
3.1a Commissioning procedure
– toxic types only
1. Open the junction box of the detector by
unscrewing the lid in an anticlockwise
direction (having loosened the retaining grub
screw first).
2. Check that all electrical connections have been made and are correct
as per Diagram 5.
3. Apply power to the detector and ensure the minimum supply voltage
of 8 V dc is present at the ‘+’ and ‘’ terminals of the detector.
4. Leave the detector to stabilise for at least 1 hour, dependant upon
sensor type.
5. Connect a digital volt meter (DVM) to the test points on the amplifier
PCB.
Note: At the test points, Zero will read 40 mV = 4 mA.
Full scale deflection will read 200 mV = 20 mA.
Zeroing the detector
6. Ensure you are in clean air. Adjust the ‘ZERO’ pot on the amplifier
(which is accessible via a hole in the PCB cover) until the DVM reads
40 mV. Check that the control equipment display reads zero.
Calibrating the detector
7. Apply calibration gas (concentration should be at least 50% of sensor
fullscale) to the detector at a flow rate of 0.5 1 litre/minute via a flow
adaptor (
Part No. C03005
). Contact Crowcon for the supply of
calibration gas.
8. Allow the gas reading to stabilise (usually 30 to 60 seconds) and adjust
the ‘CAL’ pot until the DVM reads the appropriate reading. To calculate
the reading use the formula and example below:
(
160
Range
x Gas
)
+ 40 = mV setting
Example: calibrating a 0250 ppm carbon monoxide sensor using
150 ppm gas.
3. Operation
Xgard Type 1
NB
Glassfilled Nylon
junction boxes do not
include a grub screw.
