12
3.1 Function
The product can be configured to control TDS / conductivity of water.
Once fully commissioned, the TDS value is displayed in μS/cm (or ppm if selected).
Note: Conductivity is expressed in parts per million (ppm) or micro Siemens per centimetre
(µS/cm). Micro Siemens /centimetre is becoming the more common unit, and is therefore
the default setting.
If the water conductivity exceeds the Set Point level, the TDS value shown on the display will
alternate with ‘bLd', and the valve relay will be energised until the conductivity drops below 5%
of full scale (FS) below the set point.
If the system is carrying out a purge, The TDS value will alternate with 'Pur', and the valve
relay will be energised until the conductivity drops 5% (FS) below the Set Point.
If the water conductivity exceeds the alarm level, the displayed TDS value will alternate
with 'AL', and the valve relay will be energised until the conductivity drops 3% (FS) below
the alarm level.
3.2 Inputs
The product can accept a signal from a Spirax Sarco conductivity probe (CP10 or CP30)
and a Pt100 temperature sensor. A CP32 probe may also be used with the BC3150, but will
not provide the scale monitoring and self-cleaning features.
A Pt100 temperature sensor may be connected to provide temperature compensation (2%/°C).
This is recommended if the boiler is working at varying pressures, or for other applications,
such as condensate monitoring or coil boilers, where the temperature may vary. If a Pt100 is
not fitted, the product uses a default temperature of 184°C (10 bar g).
3.3 Outputs
3.3.1 Continuous output
Used when the probe is mounted in the boiler. The probe is able to constantly monitor the
conductivity from the probe tip to the boiler shell.
3. System overview
Fig. 2 Continuous output (purge time = 0s)
Water
conductivity
SP
Hysteresis
Valve
open
Closed
High conductivity
Time
Blowdown
Keeps valve open until
conductivity drops below
hysteresis
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