Malfunction/Breakdown Of Sensor - Ofs Softening Control Instruction Manual

11.4 Malfunction/Breakdown of sensor

1. Deposits on the sensor
Precipitations and deposits on the sensor prevent an adequate monitoring.
Examples:
Rust- and iron deposits form a light red/brown coating in the flow chamber and the sensor
system
 Up streamed filters should prevent from precipitations of iron, copper or aluminum.
Biofilm growth in consequence of to high microbial count in the water
Biofilms appear highly when the softener or the measuring device has been out of operation
for some days or weeks and water was kept in the chamber.
In case of longer decommissioning time the device should be electrically disconnected.
 The sensor should be removed from the measuring chamber and stored according
storage conditions. The measuring chamber should be free of water.
2. Chlorine inrush
Chlorine addition, as often seen in raw water supply, may destroy the sensor (depending on
concentration and duration. A strong deep black colouring of the metal electrodes indicates
high chlorine influence. The sensor may indicate threshold value exceeding, while no thresh-
old value exceeding exists.
 The sensor is defective and has to be replaced.
3. Brine inrush
Should the outlet valves of the softener be defective, it is possible that during the regeneration
process but even if there is low water throughput, brine from the brine container may washed
out into the soft water, which will be evaluated by the sensor as threshold value exceeding.
With very high sodium concentration against the calcium-magnesium concentration, the sen-
sor signal will be influenced by the very high sodium content, which creates sensor error. A
high brine concentration can be measured by conductivity difference measurement between
raw and soft water. With an excessively high and concentrated brine inrush, the sensor will be
destroyed, whereby it will indicate threshold value alarm even if the softener operates proper-
ly.
 The sensor has to be replaced.
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