1
G 120
Eng. 03.91
APPLICATION
RFG749gasleakdetectorisdesignedtoensurethesafeusein
domestic and other non-industrial premises of domestic appli-
ances running on gas, such as: cookers, boilers and calorifiers.
Itisabletomonitor the concentrationinthe air oftheusual types
of combustible gases such as: town gas, natural gas, LPG and
propane.The output relay can control a safety shut-off valve, an
aeration fan or a remote alarm.
OPERATION
The LED on the facia, when lit, indicates that RFG 749 is receiv-
ing power (fig. 2.3). When the power comes on, the detector
does not activate the alarms for 1.5 - 2 minutes which is the
period necessary for the sensor to become stabilized. After this
period the detector is ready to sound the alarm.
Theinternalsensormonitorstheconcentrationlevelofgasinthe
surroundingairandthedetector,intheeventthatthisconcentra-
tion exceeds the level of alarm, sets off an audible warning and
activatesthe outputrelay which cancontrol agassafety shut-off
valve or a fan for changing air.
Thealarmlevelisequivalenttoaconcentrationof0.3%ofgasin
the air, that is, about 1/20 of the concentration necessary to
render the gas-air mixture explosive. This allows action to be
taken under conditions of maximum safety in the event of an
alarm.
Thealarmstate,onceacquired,willcontinueeveniftheconcen-
tration of gas should return below the level of alarm. In order to
reset the detector to its normal state it is necessary to press the
button located on the facia below the LED (fig. 2.4).
CONSTRUCTION
RFG 749 is constructed in two parts:
• Base (fig. 2.2) suitable for wall mounting, in self-extinguishing
plastic, comprising:
– Terminal block for electrical connections (fig.3.1) protected
against accidental contacts.
– Cable entry for passage of leads from rear (fig.3.3)
– Cable entries for passage of leads from below (fig.3.4)
– Screw holes for attaching to wall (fig. 3.5)
• Detector (fig. 2.1), enclosed in a casing made from self-extin-
guishing plastic, which includes the electronic circuit (con-
structedaccordingtostandardsofItalianElectrotechnicalCom-
mittee-CEI),thesensor,theoutputrelayandthealarmbuzzer.
On the facia are located the power supply indicator LED (fig.
2.3) and the reset button (fig. 2.4).
The output relay is airtight and is filled with inert gas which, by
preventingtheformationofsparks,ensuresthemaximumsafety
of operation.
Thecasingissecuredtothebasebyfourretainingclipsandthe
electrical connections between the electronic circuit and the
terminal block are by means of pins which are pressed directly
into the terminal sockets.
INSTALLATION
ThecorrectlocationofRFG749isessentialforitscorrectopera-
tion and depends on the type of gas to be monitored and its
density in respect of air.
RFG 749
• Power supply 220/240 Volts ac
• Internal sensor with alarm level set at 0.3% of gas in air
• Voltage-free SPDT output relay
• Suitable for control of valves N.O. or N.C. or of aeration fans
GAS LEAK DETECTOR WITH INTERNAL SENSOR
AND RELAY OUTPUT
Type of gas Position
Natural gas (light) 20 to 60 cm. from the ceiling
LPG (heavy) 20 to 60 cm. from the floor
NATURAL GAS
LPG
fig. 1
TYPICAL INSTALLATION
TO SEE A SUITABLE REPLACEMENT PRODUCT
