Pool Controls Chemigem CM55, User Manual, Page: 20 / 36

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OPERATION OF THE CHEMIGEM CM55
What is ORP?
For over 30 years operators in many parts of the world have used Oxidation-Reduction-
Potential (ORP or Redox) values as a measure of Chlorine activity in water. ORP is a
measure of the oxidising properties of the Chlorine in the water and is easily monitored by
the Chemigem probe (also called a multi-electrode). When the probe is placed into water
containing Chlorine it behaves like an electric cell and creates a small but measurable
electric voltage. This voltage is a measure of the activity (effectiveness) of Chlorine in the
water.
The Chemigem is designed to measure and automatically adjust the Chlorine and pH levels
of the water in all types of pools. Once levels are finally set or adjusted, the unit should be
left alone. The unit has been factory-set to achieve 650mV (milliVolts) Chlorine (ORP) and
7.7pH. It has been found that if ORP is maintained at 650mV, the kill time of E-coli type
bacteria is about one second. If the ORP is lowered to 550mV, the same organisms could
take up to 2 hours to be eliminated.
If the unit is used with these factory-set points as the selected levels, it should obtain
approximately 2-4ppm Chlorine and 7.7pH, providing the stabilizer level is at 50ppm. If the
stabiliser level is 30ppm or less, the Chlorine will be around 1ppm.
A test kit will measure Chlorine as parts per million (ppm) but the activity level of the
Chlorine depends upon the other materials dissolved in the pool water.
Dosing of Chemicals
Dosing of chemicals will commence a few minutes after the pool pump has been switched
on to allow for adequate mixing and accurate sensing. Similarly, the safety warning
sounds and alarm signals will not operate for the first 4 minutes.