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3
Operation
Revision 2
©
Moffat Ltd, August 2012
Cobra Series Gas Barbeque
Electromagnetic Flame Failure Gas Valve
The purpose of the safety valve is to shut off the
flow of gas if the pilot flame goes out.
Inside the body of the gas valve is an
electromagnet connected to a spring loaded
plunger. When the electromagnet is energized, it
holds the plunger in, allowing gas to flow through
the valve. When the electromagnet is
de-energized, the plunger snaps to the closed
position, stopping the flow of gas.
Millivolts are provided to the electromagnet by
the thermocouple (not shown) which generates
millivolts when heated. The thermocouple screws
into a fitting at the back of the gas valve to make
an electric connection. By pressing in the gas
control knob, the plunger can be temporarily held
open while lighting.
There are two reasons for this; firstly, gas has to
flow through the safety valve to make it possible
to light the pilot burner, and secondly the plunger
has to be pushed all the way in for the
electromagnet to hold it in. i.e. the
electromagnet is strong enough to hold the
plunger in once there, but is not strong enough
to pull it in by itself.
Sometimes a problem with the flame not staying
lit after releasing the button can be attributed to
not pushing the plunger all the way in.
Figure 3.2b.
Thermocouple
Gas flow
Electromagnet
Plunger
Shaft
Knob
Gas flow
Plunger