Automatic chemical controllers

by Sally Bouorm | August 1, 2010 8:57 am

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By M. Troy McGinty

Automatic pH and oxidation reduction potential (ORP) controllers were introduced to the pool industry more than 40 years ago and have been assisting pool operators with the ongoing challenge of maintaining safe water ever since. They are no longer mysterious pieces of equipment; since their introduction, these devices have been mandated in the United States by 11 state health departments, and supported and recommended by the remaining 39 states and all Canadian provinces and territories.

With protozoa like Giardia, viruses like Norovirus and bacteria like E. Coli being introduced into recreational water every day (in most cases unknowingly), careful attention must be given when dealing with recreational water sanitation. Chemical controllers help regulate pH and sanitizer levels to eliminate and prevent the transmission of infectious diseases, which in turn saves lives.

How do they work?

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An automatic chemical controller uses sensors (probes) to continually measure two parameters—pH and ORP.

pH

Defined as the negative logarithm of the hydronium ion (H₃O⁺) activity in an aqueous solution, pH essentially measures how much acid (hydronium ion) is contained in the water by using a zero to 14 logarithmic scale.

By virtue of its logarithmic nature, pH is a dimensionless quantity; readings can vary depending on water temperature. Pure water at 25 C (77 F) usually has a pH around seven. If readings are lower than this median level, the water is acidic, while readings above seven show the water to be basic/alkaline. In comparison, the average human tear has a pH between seven and 7.6. However, in the pool industry, the magic number is 7.5, as this is the level where bather comfort and the activity of hypochlorous acid (HOCl) and the hypochlorite ion (OCl^–) work best together.

There are two reasons why swimming pool water pH should be kept in the seven- to 7.6-range. First, the water will be less likely to irritate bather’s eyes and/or skin and secondly, this range allows pool operators to maintain effective sanitization levels. A hydrogen atom (¹H) bound to OCl^– is more effective at inactivating disease-causing germs than OCl^– on its own. Without proper pH, all other water chemistry parameters fall out of balance and safe/comfortable water becomes unattainable.

ORP

The second parameter an automated chemical controller monitors is ORP, which measures the potential of the oxidizer present in the water to remove electrons from unwanted substances. Once the unwanted substance loses its electron, its chemical structure is changed and it is incapable of being infectious.

Unlike the reading from a N, N-diethyl-p-phenylenediamine (DPD) test kit, ORP provides a true measurement of a sanitizer’s effectiveness based solely on its ability to oxidize in a specific body of water—even in the presence of other variables, such as cyanuric acid, non-chlorine oxidizers, etc. In the pool and spa industry, oxidation reduction potential is measured in millivolts (mV). A 650-mV reading has been widely accepted as the industry standard, since this level suggests the water is in satisfactory microbial condition.

Correlation between water quality parameters important

The relationship between pH, ORP and free available chlorine (FAC) is very important. Pool water must be kept more acidic (a pH level of 7.5 or lower) to make sure the HOCl remains active. This increases the sanitizer’s oxidation ability to destroy and deactivate a wide range of potentially dangerous bacteria and viruses. This, in turn, also raises the ORP reading.

As ORP sensors (probes) are able to provide a good estimation of water sanitizer levels, automatic chemical controllers have become an integral component of the equipment room. They assist commercial pool operators by keeping a ‘watchful eye’ over water chemistry and take the guesswork out of maintaining healthy water conditions. It is impractical, and likely impossible, for pool operators to manually test pH and chlorine levels and add the requisite chemicals every minute, every day. A controller, on the other hand, recognizes any changes in sanitizer and/or pH levels and sends a signal to the chemical feed equipment to add more sanitizer and maintain the preferred water chemistry.

Automation benefits

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Once one understands what an automatic chemical controller is monitoring, its ‘primary’ benefits for a commercial aquatic facility can be discussed. First and foremost is bather and operator safety; a chemical controller helps maintain water quality and reduces human contact with chemicals. Manual handling and broadcasting of chemicals is also minimized, reducing the exposure and risk to employees.

Another benefit these devices offer is the probability of reducing chemical usage by more than 30 per cent. Using a process termed ‘proportional feed,’ controllers are able to make feed decisions every minute, therefore eliminating the addition of too much chemical.

The device’s ability to keep swimming pool water in balance by maintaining precise chemistry also decreases the water’s chances of scaling or becoming corrosive. As such, controllers have also been shown to increase the lifespan of the swimming pool (structure), its surface and equipment. Using the proper amount of chemicals also allows the facility to operate in a more efficient and eco-friendly manner.

Evolution of the chemical controller

Automatic chemical controller technology has evolved considerably over the past 40 years. They started as very large analog units that were not very accurate, susceptible to the aggressive pump room environment and in need of constant calibration.

Today’s microprocessor-based controllers, however, are quite different and have revolutionized pump room automation by offering facility operators new benefits, as well as improved reliability and accuracy. This technology has allowed manufacturers to add self-calibrating capabilities, along with user-programmable options to help maintain healthy pool water.

Additional inputs and outputs were added in conjunction with the microprocessor, which extended the controller’s capabilities far beyond its original duties. To further assist commercial pool operators, these devices are now equipped with the following features:

• Over-feed timers, which protect against over-shooting pH and sanitizer levels;
• pH priority, which protects new plaster or gunite applications during the curing process;
• pH and ORP high/low alarms, which protect bathers from unsafe water conditions;
• True free chlorine readings;
• Conductivity sensors, which measure total dissolved solids (TDS) or salt concentration;
• The ability to turn on/off salt chlorine generators;
• Water level control;
• Litres/gallons per minute (lpm/gpm) flow rate sensing;
• Water temperature control, with the ability to turn a heater on/off;
• Backup chlorination with secondary set-points for use in any application, especially salt chlorine generation;
• Auto backwash;
• Solution tank level sensing, with alarms;
• Safety vacuum release system (SVRS) alarm sensing;
• Alternative sanitizer control (e.g. supplemental systems, such as ultraviolet [UV] and ozone technology);
• Langelier Saturation Index (LSI) calculations;
• Pump room flooding sensors with alarm and protection; and
• Remote alarm notifications for all statuses.

One of the most important advancements microprocessor technology has given automatic chemical controllers is the ability to communicate with external peripherals and personal computer interfaces.

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First-generation chemical controllers were equipped with digital communication capabilities limited to data ports with telephone or local area network (LAN) lines. This enabled the controller to communicate with a computer using designated software, which allowed users to download water chemistry parameters and other readings to their computers for logging purposes. Installing telephone and/or LAN lines in a commercial pump room was not always an easy task, while keeping software updated was difficult due to the rapid changes in applications.

As the communication industry advanced, so did automatic chemical controller technology. Today, pool operators and service companies can communicate with these devices via a variety of wireless protocols (e.g. cellphones, wireless network [Wi-Fi] and satellite), thus eliminating the need for telephone and/or LAN line installations.

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Wireless communication has further reinforced the importance of automatic chemical controllers in the pool industry, as it gives the pump room a ‘voice.’ With the addition of web-based software applications, which eliminate the need to install/update software on individual computers, these technologies allow anyone to monitor water chemistry and other important parameters from any computer terminal in the world, simply by typing in a designated user name and password.

Newer controllers can also be programmed to automatically send remote alarm notifications to any e-mail or cellphone to notify an operator of a chemistry-related issue or operating problem.

The job of today’s automated chemical controllers is progressing from pH and ORP control and slowly migrating into full pump room monitoring, operation and communication. This progression will allow facility operators and swimming pool service companies to be more proactive and efficient while maintaining safe, healthy swimming pool water.

 

M. Troy McGinty is the water quality management consultant, Poolcomm administrator and product instructor for Hayward Commercial. He is a Certified Pool Operator/Instructor (CPOI), Aquatic Facility Operator (AFO) and has led numerous seminars and training sessions across North America on the topic of pH and ORP automation, communication and business development. He can be reached via e-mail at mtmcginty@haywardnet.com[6].

Source URL: https://www.poolspamarketing.com/trade/automatic-chemical-controllers/

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