Chemtrol Pool Controller: Difference between revisions
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In the configuration used at Fairway Farms, it samples ORP (oxidizing properties of a sanitizer, such as chlorine) and pH. It adds calcium hypochlorite (via the "chlorinator") and/or hydrochloric (muriatic) acid (via the "acid pump") to the pool as part of a closed-loop system. | In the configuration used at Fairway Farms, it samples ORP (oxidizing properties of a sanitizer, such as chlorine) and pH. It adds calcium hypochlorite (via the "chlorinator") and/or hydrochloric (muriatic) acid (via the "acid pump") to the pool as part of a closed-loop system. | ||
== | == Operation == | ||
=== | === Alarms === | ||
An alarm has been configured to sound when a measurement parameter (pH, ORP, TDS or flow rate) is far out of normal operating bounds. | |||
The | The parameter that is responsible for the alarm will flash on the Chemtrol LCD display. Note that it is normal and expected for the unit to alarm when the main pump is stopped. | ||
=== Bypass Line Flow === | |||
Due to the large diameter of the water piping in the system, direct measurement is not possible. Therefore, a "bypass line" (a 1/2" plastic pipe tapped off of the post-filter pipe) supplies water to the sensor probes. An inline flow meter identifies the rate of flow to the probes. If insufficient flow is present, the sampled water may not have the same properties of that in the main piping. This is potentially a dangerous situation - as excessive chemical dosing could occur (with no feedback). To prevent this, the Chemtrol halts all chemical dosing when the flow is below a certain threshold. | |||
When there is insufficient flow, the message "Bypass Line" is shown at the bottom of the display. This also triggers an alarm (if configured). | |||
According to the manual, the flow should be able 2-3 GPM. In our system, up to 5-6 GPM seems to be a better target (when the system flow is optimal), allowing some margin. It is critical that there is enough flow to fully submerge the probe tips at all times to avoid damage. | |||
== Procedures == | == Procedures == | ||
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On the main screen, an "A" to the right of the pH reading indicates that the acid pump is enabled (automatic control), "X" indicates it is disabled. | On the main screen, an "A" to the right of the pH reading indicates that the acid pump is enabled (automatic control), "X" indicates it is disabled. | ||
== Instrumentation == | |||
=== Chemical Probes === | |||
The ORP and pH probes are said to be rated for a year of use. In reality, they will probably last longer. Probes should be replaced when readings do not align with those from the chemical test kit (and cannot be corrected for via calibration). | |||
The [http://www.sbcontrol.com Chemtrol] branded probes are quite expensive. We have had good success with probes (installed in the 2020 season) from [https://sensorex.com/ Sensorex]. The cost is about 75% less than those from Chemtrol. | |||
* pH5000 Polycarbonate Swimming Pool pH Sensor ($56 as of May 2020) | |||
* ORP1000 Polycarbonate Laboratory ORP Sensor ($86 as of May 2020) | |||
=== Flow Meter === | |||
The flow meter validates the presence of fresh sampled water in the "bypass line" for monitoring by the Chemtrol unit. The flow meter is a [https://www.gemssensors.com/search-products/product-details/rfo-type-electronic-flow-sensor-155481 Gems RFO-Type 155481]. This particular model is what was installed during a service call by Aquatic Source in August 2016. It was subsequently replaced with an identical model in April 2021. The failure seems very premature; the unit no longer produces pulses on its output. An initial tear-down/diagnosis shows no obvious root cause. | |||
The flow meter is an absolute necessity for automated chemical control. Due to the large main re-circulation lines in the system (larger than 2 inches), a bypass line is used to provide an alternate path to the pH and ORP sensors. The flow meter verifies that sufficient flow is present in this bypass line (such that the measurements reflect the chemical levels in the main re-circulation line and pool). | |||
The flow meter for the bypass line can be disabled under certain circumstances. However, this must be used with extreme caution, as operating a chemical feed without sufficient monitoring could cause dangerous/damaging chemical reactions. | |||
Upon installing the newest unit (April 2021), the bypass flow rate read-out was adjusted. Per the datasheet for the 155481, the unit produces 225 Hz (pulses/second) for a 20 GPM flow rate. The Chemtrol requires a value in "pulses per unit volume". In this case, 225 Hz / 20 GPM = 11.25 Hz/GPM, or 11.25. Prior to April 2021, a default value of 1 was used, resulting in a typical (incorrect) readout of 0 to 1 GPM. | |||
The wiring for the flow meter is shown in the "PC2100 Auxiliary" (page 43), as part of the [[Pool_Systems_Automation#Auxiliary|Pool Systems Automation Drawings - Auxiliary]] package. | |||
== Technical Information == | == Technical Information == | ||