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3.1 Function
The product compares the input signals with the Set Point to control the water level in the
boiler tank, or vessel, by operating a pump, valve, or solenoid.
On / off control
-
Pump control.
-
Two alarm outputs.
-
4 - 20 mA level retransmission output (isolated).
Note: A solenoid valve may be used instead of a pump.
Modulating control
Modulating valve control using valve motor drive (VMD) or 4 - 20 mA control signals:
-
Two alarm outputs.
-
4 - 20 mA level retransmission output (isolated).
Two or three element modulating control
Modulating valve control using valve motor drive or 4 - 20 mA control signals:
-
Two alarm outputs.
-
4 - 20 mA level output (isolated).
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Feedback from steam meter.
-
Feed forward from water meter.
3.2 Inputs
The product has three inputs to accept the following signals:
-
Level probe or transmitter 1-6 V or 4-20 mA outputs.
Note: The level probe must be long enough to sense over the complete level range.
-
Steam meter 4-20 mA output to compensate for the rise in water level due to increased
steam demand (Two element control).
-
A signal from a water meter to compensate for variations in feedwater flow rate (Three
element control).
3.3 Outputs
The product control signal can be configured / wired to work with a pump or a modulating
control valve. It also provides relay outputs for high and low level alarms and can provide an
isolated 0-20 mA or 4-20 mA retransmission output.
Parameters can be remotely accessed via the RS485 / MODBUS communications.
3. System overview
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