20
Modulation
During stage 12 (modulation), the unit will position the fuel and air motors as programmed for the
profile selected.
In auto modulation mode, the system will modulate as necessary to either track the input or maintain
the pressure/temperature of the boiler at the entered setpoint (See Option parameters section). If
boiler sequencing is enabled and active, the unit will start, stop and modulate according to instruc-
tions issued from the unit controlling the lead boiler.
In manual modulation mode, the system will either modulate in response to the keyboard up/down
keys or the external up/down signals.
Safety Shutdown (Burner Lockout)
A safety shutdown will occur under the following conditions:
•
In stages 5, 6, 7, 8, 10, 11, 12, or 14, if a drive is not in the correct position.
•
During stage 6, a drive speed has been measured to be outside the allowable range.
•
During modulation (stage 12), an oxygen trim limit has been reached, and this has been config-
ured to shut the burner down (see option parameter 39.0).
•
In any stage, if an internal or external fault not previously mentioned occurs which may affect
the safe operation of the burner.
The display is a 2 line 20 character per line dot matrix vacuum fluorescent unit allowing the use of
plain text messages for most display parameters. The display must be fitted to allow commissioning
of the system but once commissioning has been completed, the display may be removed, providing
either the control unit lamps and external switches and/or lamps are fitted for fault indication and
reset.
