5.6 Shunt Switch
5.6.1 Shunt Switch Philosophy
The ability to implement a controlled by-pass of the low water cut off’s during a manual water column
blowdown, boiler blowdown or evaporation test is available on the Mk7 M.M. with water level
control. This is incorporated into the Autoflame controller so as to avoid the requirement for any
additional push buttons/key switches on the control panel. The operation of the shunt switch can only
be accessed in Mk6 mode. Please follow this procedure:
1. While the burner is either firing or in the standby state, press the ‘Water Level’ and ‘Enter Memory’
buttons simultaneously.
2. The Mk.6 screen will show “Implement level Control Test Procedure”.
3. The operator will have to either confirm that he wanted to proceed by pressing ‘Water Level’ and
‘Enter Memory’ simultaneously or press ‘Run’ to exit.
4. If the operator proceeded to press the ‘Water Level’ and ‘Enter Memory’ button, the Mk.6 screen
would then display ‘Feed Water Valve Shut’ and close the feed water valve.
5. The burner would continue to operate. At this time the operator would either let the water evaporate
automatically or physically blow down the water column or boiler. A user-definable amount of time
(time A) is set in expansion option 25.1, during which time the 1st Low must be reached. If not, the
burner will revert back to the run condition.
6. The 1st Low Alarm would be initiated and the alarm would sound. The operator has the option of
muting the alarm. The burner continues to operate.
7. The operator would continue to decrease the water level in the column or boiler or allow the water
to continue evaporating. A user-definable amount of time (time B) is set in expansion option 25.2,
during which time the 2nd Low must be reached. If not, the burner will turn off.
8. The 2nd Low Alarm would be initiated and the alarm would sound. The operator again has the
option of muting the alarm. The burner continues to operate.
9. 3 seconds after the 2nd Low Alarm has been initiated the Mk.6 screen would display ‘Feed Water
Valve Open’. The water level would start to increase.
10. The Mk.6 would expect to see the water level rise above the 2nd Low Level within 300 seconds
(default value) or time B of the valve opening. Should the level not increase a 2nd Low Alarm will be
initiated, causing the burner to turn off and a lockout to occur, requiring a manual reset to recycle the
system.
11. Once the water level increased above the 2nd Low Level the Mk.6 would allow a further 300
seconds (default value) or time A for the water level to rise above the 1st Low Level. Again should the
level not increase a 1st Low Alarm will be initiated, causing the burner to turn off and an alarm to
sound. The system would automatically recycle the system once the water level is above the 1st Low
Level.
12. Once the level returns to above the 1st Low Level the screen would display ‘Test Complete, Normal
Operating Level Restored’
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