AUTOFLAME Mk8 MM Installation And Commissioning Guide

6 Draught Control
04.09.2016 Mk8 MM Expansion Features Installation and Set-Up Guide Page 103
6.2 Draught Control Operation
6.2.1 Overview
To activate draught control on the Mk8 MM, the Draught Control expansion software feature must be
unlocked. The activation code for the serial number of the MM will need to be purchased using part
number MK8005, and uploaded to the unit via Download Manager software.
Please see Autoflame PC Software Guide for more information on unlocking expansion features on the
Mk8 MM using Download Manager software.
The draught servomotor can be set on the Mk8 MM for servomotor movement only or draught control
with a pressure sensor to maintain the stack pressure.
The draught control trim functionality follows the same ideology to the EGA, where corrections are
made to air damper to compensate for the changes in exhaust gas values from their commissioned
values, caused by fluctuations in ambient conditions. For Autoflame draught control, corrections are
made to the stack damper to compensate for changes in wind and ambient conditions which cause the
stack pressure to differ from the commissioned stack pressure along the fuel curve.
Once the burner starts up and the main flame stabilised, there is a time delay where no draught control
operation occurs, set in expansion option 85. After this time delay elapses, as the air going into the
burner is increased from low fire to high fire, the boiler pressure may change and the draught
servomotor will move to follow these changes as commissioned. If the atmospheric or stack pressures
have changed from their commissioned values along the curve, the air damper will either move in the
open, or close direction to adjust the air pressure in the stack back to its set value.
The smallest angle that the draught damper can drive to while running is defined by expansion option
83; when the burner turns off, the draught damper will go to commissioned closed position to maintain
heat within the boiler.
If draught control is optioned off after being commissioned, then the draught servomotor will continue
to move to its commissioned angular position as the burner fires.
6.2.2 Deactivation Window
There is a deactivation window, outside of which no trim occurs, and the air damper remains at the
previously trimmed position until back within the window and trim is required. This deactivation window
is defined by expansion options 85 - delay before compensation and 86 – commissioned angle
variation tolerance. If the draught servomotor has moved more than the set angular degrees “x”,
within the time period set “y”, than no trim functionality will operate, if trim has been performed prior
to this deactivation then the trim is carried forward.
For example, when the burner is first switched on, if the burner comes out of warming in lead-lag
control, or is switched from low flame hold to auto mode, there is a high load demand. In these
situations the firing rate may ramp up quickly to meet load demand, at this point if the draught
servomotor is required to move greater than the commissioned angle variation tolerance and quicker
than the delay before compensation then no trim functionality will occur and any trim % will be carried
forward.

AUTOFLAME Mk8 MM Specifications

General

Brand	AUTOFLAME
Model	Mk8 MM
Category	Controller
Language	English