4 Top Blowdown
04.09.2016 Mk8 MM Expansion Features Installation and Set-Up Guide Page 77
4.3.4 Configuration
The table below indicates the terminals on the MM allocated for top blowdown control.
Terminal Description
P- 0V supply to top blowdown and feed water servomotors
FW Signal from top blowdown servomotor, indicating position
P+ +12V supply to top blowdown servomotors
3P+ +9V supply to TDS probe
3P- 0V supply to TDS probe
3T+ Digital communications connection from TDS probe
3T- Digital communications connection from TDS probe
TB Switched neutral – top blowdown contactor
TBI Switched neutral – drives top blowdown servomotor clockwise
TBD Switched neutral – drives top blowdown servomotor counter clockwise
The table shows the expansion options which will need to be set for using top blowdown control.
Expansion Option Description Setting
40 Top blowdown function 1,2 or 3 as required
41 TDS units As required
42 TDS target As per boiler manufacturer’s specifications
43 TDS temperature compensation As required
44 TDS ppm conversion As required
45 TDS adjustment As required
46 TDS warning level As required
47 Pressure threshold As required
48 Sample time As required
49 Settle time As required
50 Measurement time As required
51 Blowdown time As required
52 Proportional band As required
53 Integral time As required
54 Derivative time As required
55 Servo open angle As required
The top blowdown control will only make corrections to the open time of the solenoid/2-state
servomotor or the modulating servomotor in the blowdown time, if with the TDS is within the
proportional band set in expansion option 52. If the TDS is above the proportional band offset above
the target TDS value, and the valve will remain solenoid valve or top blowdown servomotor will remain
fully open. For a quicker response to fast changing TDS, decrease the integral time set in expansion
option 53, to prevent overshoot, a derivative time can be added in expansion option 54.
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