3. OPERATION
2. INSTALLATION (continued)
5. SPECIFICATION
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.
Note: Cirrus is factory calibrated to detect the required flammable gas
and provide a 4-20 mA output proportional to 0-100% LEL of that gas.
The control panel which is used to indicate the gas concentration should
be pre-configured to accept 4-20 mA input prior to connection of Cirrus.
Please contact the supplier of the control panel being used for
assistance.
3.1 Initial Start Up
Prior to switching on Cirrus for the first time, inhibit any local control
functions from the control panel to which Cirrus is connected.
Once field cabling is complete and connections have been
checked, the 24 V dc supply may be switched on. After switch on, Cirrus
performs a self check routine. Leave Cirrus to warm up for 10 to 15
minutes approximately.
After the warm up period Cirrus is fully operational and the
output signal is proportional to the concentration of hydrocarbon gas or
varpour present at the detector. As standard Cirrus provides a 4-20 mA
signal proportional to 0-100% LEL methane (for calibration purposes 5%
VV = 100% LEL). Other calibrations are available and the specification
for each instrument should be consulted to discern the correct operation.
If the output reads other than 4-20 mA see Section 3.3 ‘Fault Diagnosis’.
3.2 Normal Operation
Cirrus includes a tricolour LED visible through the quartz window of the
detector with the Weatherproof Cover removed. The LED gives the user
basic information concerning the state of the detector. This is
summarised in Table 2 on page 10.
Operational
LED indication
Detector
Comment
state
output
Start up
Flashing green
2 mA
1 minute
Normal
Green continuous
4.0-11.2 mA
-5–45% LEL
Normal
Red/green alternate 11.2–12.8 mA
45–55% LEL
Normal
Red continuous
12.8–20.8 mA
55–105% LEL
Detector fault Amber continuous
0 mA
Unrecoverable fault
Dirty optics
Flashing amber
2 mA
Recoverable fault
Over range
Flashing red
> 22 mA
Table 2:
LED status indication
3.3 Fault Diagnosis
Cirrus is designed to provide user free operation and includes a number
of diagnostic routines which are transparent to the user. Two types of fault
condition may occur, one is
‘dirty optics’
indicated by a 2 mA signal and
the other is an unrecoverable fault signalled by 0 mA.
Cirrus continuously checks that the optics are clean. Should the
optics become blocked or obscured by more than 75% the 4–20 mA
output is clamped to 2 mA signalling a beam blocked condition. This may
be cleared by removing the Weatherproof Cover and cleaning the optics
with an IPA impregnated lint free cloth. It is advisable to inhibit the control
panel before cleaning the optics.
If the output is 0 mA then remove power from the detector, wait 15
seconds and reconnect the power. If after carrying out the self check
routine (1 minute) the output remains at 0 mA, it is worthwhile checking
that the optics are clean, the supply voltage is correct and that the
operating temperature is between -40°C and +65°C. If these are correct,
the detector should be removed and returned to Crowcon for repair.
Description
Part Number
Weatherproof cover
S01721
Calibration cover
C01660
Flow adaptor
C01659
Pellistor mimic
C01648
5 mm Hex wrench
M07172
Calibration gas
Contact Crowcon
3.4 Functional Testing
Prior to testing Cirrus inhibit any local control functions from the control
panel to which cirrus is connected.
Site procedures may dictate that the system be tested
periodically with the target gas. A Calibration Cover (part no. C01660) is
available which slides over the Weatherproof Cover. The cover has a
6mm OD compression fitting on the inlet and a 10 mm OD compression
fitting on the outlet. Test gas may be plumbed to the cover and gas
applied at a flow rate of 1.5 to 2.5 litres/minute for 1 minute. 50% LEL gas
in air is recommended.
3.5 Maintenance
There are no user serviceable parts in Cirrus. Maintenance is limited to
the cleaning of optics as and when required. The use of a lint free IPA
impregnated cloth is recommended for cleaning of the optical surfaces.
Function
Detection of hydrocarbon gases in the
0–100% LEL range by infrared absorption
Optical system
Dual beam, dual wavelength, dual detector
with fuzzy optics
Operating voltage
18–32 V dc (nominal 24 V)
Typical outputs
All levels configurable:
0 mA; fault
2 mA; dirty optics
4-20 mA; 0–100% LEL
22 mA; over range
Response time
T90 < 10 sec. (inc. Weatherproof Cover)
Communications
Modbus (RS485) serial link
Dimensions
240 x 130 x 175 mm (9 x 5.2 x 7 inches)
Weight
7 kg (15.4 lbs)
Construction
Stainless steel 316 ANC4
General immunity
Immune to sunlight and all catalyst poisons
RF radiation
Tested to EN55022 class B and meets
EN50081-1
RF immunity
Tested to IEC801-3 and meets EN50082-2
Temperature range
-40 to +65°C (-40 to +149°F)
Humidity range
0–99% RH non-condensing
Approval codes
II 2 G EEx d IIC T6 (+65°C), T5 (+80°C
Tamb = –40 to +65°C (–40 to +149°F)
UL Class 1, Zones 1 & 2
Safety Cert No.
Sira02ATEX1284
Ingress Protection
IP66 and IP67
Zones
Certified for use in Zone 1 or Zone 2 areas.
(see area classifications section)
Gas groups
IIA, IIB, IIC
3. OPERATION (continued)
4. SPARE PARTS AND ACCESSORIES
7
8
9
10
11
12
13
Diagram 3:
Electrical connections
NOTES
Area Classifications:-
Zone 0:
An area classified, as Zone 0 will have ignitable
concentrations of flammable gases, vapours or
liquids present continuously or for long periods of
time under normal operating conditions.
Zone 1:
An area classified, as Zone 1 is likely to have
ignitable concentrations of flammable gases,
vapours or liquids present under normal operating
conditions.
Zone 2:
An area classified, as Zone 2 is not likely to have
ignitable concentrations of flammable gases,
vapours or liquids present under normal operating
conditions.
Terminals 5 to 10 are reserved for digital communications and
must not be used to terminate spare cores.
Note: The junction box and cable armour must be earthed at either the
detector or control panel to limit the effects of radio frequency
interference. It is good practice to provide the earth connection at the
safe area only, so as to avoid earth loops.
2.5 Connection of the Detector to the Docking Station
Ensure that power to the detector is isolated at the control panel. Prior to
installation of the detector check that all electrical connections to the
docking station are correct.
The detector is connected to the docking station via a flying
lead terminated in a 9 way D type connector. This connector is plugged
into the docking station’s female connector and secured using the two
retaining screws supplied. The unit is fixed securely to the docking
station with four M6 screws.
