AUTOFLAME Mk8 MM User Manual

10 Water Level Control
Mk8 MM Manual Page | 167
10.3.3 Feed Water Control
The boiler feed water can be controlled using:
• Pump on/off only
• Pump on/off and servomotor control
• Pump on/off and VSD control
• Pump on/off, servomotor control and VSD output
The table below shows the terminals on the MM allocated for the feed water control parts.
Terminal
Description
P-
0V supply to top blowdown and feed water servomotors
P+
+12V supply to top blowdown and feed water servomotors
TW
Signal from feed water servomotor, indicating position
I+
Current output, 0-20mA or 4-20mA to feed water VSD or servomotor
V+
Voltage output, 0-10V or 2-10V to feed water VSD or servomotor
IV
Common terminals for I+ and V+
BFW
Feed water pump contactor
The table below shows the expansion options relating to feed water control.
Expansion Option
Description
2
Feed water control element
10
Pump turn off point
11
Pump turn off percentage
12
Pump turn on percentage
13
Feed water control proportional band
14
Feed water control integral time
15
Feed water control derivative time
16
Feed water servo open angle
20
Burner operation on feed water control fault
The feed water pump can be set so that it turns off and on at percentages above and below the control
point/high water, via the feed water pump contactor on terminal BFW.
If the feed water control is set with servomotor or VSD, then the 3-term PID control will operate. The
proportional band set in expansion option 13 is the percentage between the control point and 1
st
low level
where corrections are made to the servomotor/VSD to maintain the control point; outside of the p-band, the
servomotor/VSD will remain fully open. The integral time set in expansion option 14 will set how fast the
system responds to feed water changes; for a slower response increase time, and vice versa for a faster
response. The derivative time set in expansion option 165 is used when a quick response is required but
where overshoot is undesired; the water level should not rise too high above the control point, so the
derivative element will need to be enabled.
The feed water servomotor closed position is set by zeroing the potentiometer in Commissioning mode,
however the open position is set in expansion option 16.

AUTOFLAME Mk8 MM Specifications

General

Brand	AUTOFLAME
Model	Mk8 MM
Category	Controller
Language	English