4 Fuel Output Modes and Changeover Options
Mk8 MM Manual Page | 110
4.4.3 Commissioning in DFOM
When using Dual Fuel Output Mode, any fuels used must be commissioned in Dual Fuel Output Mode,
therefore fuels commissioned in SFOM will require recommissioning.
Fuel 1 uses channel 1 for fuel and channel 2 for air. Channel 3 is not available when running fuel 1 since it is
permanently assigned to fuel 2. When commissioning fuel 1 the closed position for servo channel 3 should
be set, but it will not be possible to move servo channel 3 after this.
Fuel 2 uses channel 3 for fuel and channel 2 for air. Channel 1 is not available when running fuel 2 since it is
permanently assigned to fuel 1. When commissioning fuel 2 the closed position for servo channel 1 should
be set, it will not be possible to move servo channel 1 after this.
IMPORTANT: If a VSD is used to control the air fan in addition to the air damper servo, it is very
important to have similar VSD signal output on both fuels commissioned in Dual Fuel Output Mode.
4.4.4 Fuel Changeover Process in Dual Fuel Output Mode
On a system configured in Dual Fuel Output Mode, when fuel select is triggered on the MM, fuel changeover
will only take place if the MM is in one of the following modes:
• In normal “Run” mode the fuel can be changed while the burner is in the Recycle or Standby states.
• In “Commission Mode” the fuel can be changed while in the commission menu screen (but not in the
commissioning screen).
• In “Run” mode if the fuel input is changed while firing, it will cause a burner shutdown, allowing the
fuel to be changed when Recycle/Standby state is reached.
The selected fuel must be commissioned in Dual Fuel Output Mode, if the newly selected fuel is not
commissioned then a warning will appear indicating that the selected fuel cannot be run and the MM will
continue in its current mode running on the same fuel (if the burner is firing then it will continue to fire on the
current original fuel). This warning will clear automatically when the fuel selection is returned to the current
fuel.
If the burner is firing and the newly selected fuel has a gas pressure sensor optioned then a fuel pressure
test will take place. The supply-side fuel valve for the newly selected fuel is briefly opened and the fuel
pressure is measured. If the fuel pressure is within the optioned limits of the commissioned pressure for the
new fuel then the fuel changeover process may continue, otherwise the MM will continue to fire on the
current fuel. This does not happen if an oil fuel is selected.
Failure of a gas pressure limits test at this point will trigger a warning indicating that low gas pressure
prevented a fuel changeover. This warning will clear automatically when the fuel selection is returned to the
current fuel. Selecting the new fuel again will perform another gas pressure test.
If the burner is firing and a burner shutdown is triggered, the shutdown will follow any optioned procedures
such as low-fire shutdown, post-purge, valve proving, etc. If the current fuel is reselected while the burner is
still firing the fuel change shutdown can be cancelled.
Once the MM reaches the Recycle/Standby state, the fuel changeover takes place and the burner will restart
on the newly selected fuel.
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