Pool Systems Automation

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As of December 2020, a project is underway to add monitoring and control automation to the pool systems. This is strictly a volunteer effort, at no cost to the club.

The reasons for this system are as follows:

  • To monitor staff and key maintenance personal of abnormal operating conditions or situations requiring attention.
  • To protect aging equipment (i.e. the boiler) from damage due to malfunction.
  • To reduce staff workload by automatically filling the pool.
  • To record historical data for pressure, flow, temperature and chemical levels.

The following principles have driven and will drive all future design efforts:

  • The system must not hinder or add complexity to daily pool maintenance.
  • In the event of automatic system failure, manual systems (gauges, valves) should be usable to perform all tasks.
  • The system must be very well documented and maintainable by moderately technical member-volunteers.


A DirectLogic 06 (D0-06DD2) programmable logic controller (PLC) is used for as the base for monitoring and control. A PLC was selected due to its reliability and relative ease-of-maintenance by volunteer maintenance staff. Within the electrical engineering community, most have had some level of experience with PLCs and/or ladder logic. It is assumed that within the membership, there will always be someone with the knowledge that can volunteer on an as-needed basis.

The controller consists of an internal CPU, 24V inputs/outputs (I/O) and multiple add-on modules for analog measurements. Serial communication carried over WiFi via a Lantronix PremierWave XN, presenting the PLC as if it were connected to a virtual communication port on the host PC.


The following points, as shown in the Process Flow Diagram, are monitored by the PLC:

  • 4 x Pressure Transmitter (PT) units, one per filter tank. Each unit is connected in parallel to a non-electrical gauge.
  • 1 x Flow Transmitter (FT) unit prior to the pool return. A manual gauge is placed in the vicinity of this paddle-wheel sensor.
  • 2 x Depth Transmitter (DT) units, placed near the bottom of the surge tank and in the static level probe well. The latter is optional (may not be implemented).

There are additional sensors, not directly monitored by the PLC, but considered to be part of the system:

  • 1 x Temperature Transmitter (TT) prior to the inlet of the boiler. This unit is used as the feedback for the temperature controller, which raises a call for heat to the boiler.
  • 1 x Flow Transmitter (FT), pH probe and ORP probe. These sensors are fed into the Chemtrol PC2100.

The following sensors are used:

Parameter Sensor Part Range Output
Pressure Measurement Specialties MSP-300-100-P-4-N-1 0-100 psi 1-5 V analog
Flow (Output) GF Signet MK515.3P1 0.3 to 6 m/s
1 to 20 ft/s
Sine Wave (analog)
Depth ALS-MPM-2F 0-5 meters 4-20 mA
Temperature TBD - PT100 RTD -40 to +400 degC Resistive

Sensors connected directly to the Chemtrol PC2100 are detailed here.

Stack Light

The stack light indicates the overall operating state of the system.

State Description
None The system is off or the pump is starting up.
Solid Green The pump and system are operating nominally.
Flashing Green Same as Green with active pool fill.
Solid Yellow The pump and system are operating but intervention may be required.
Flashing Yellow Same as Yellow with active pool fill.
Solid Red The pump is stopped by the operator.
Flashing Red The pump is stopped due to the surge tank level.


Drawings have been updated as of January 23rd, 2021 with multiple corrections and as-built updates. They are still in-process and subject to review and change.

Panel Layout

Pages 5-9 are reserved for enclosure panel layouts.

FFSC-001 Pg 5 - PLC Panel Layout.png


Pages 10-19 are reserved for sensors (including "flow meters") and their associated cabling.

FFSC-001 Pg 10 - Filter Tank Pressure Sensors.png FFSC-001 Pg 11 - Flow Meter.png FFSC-001 Pg 12 - Water Level Sensors.png FFSC-001 Pg 13 - Water Level Probe.png

Programmable Logic Controller (PLC)

Pages 20-29 are reserved for the PLC and its expansion modules.

FFSC-001 Pg 20 - PLC Base.png FFSC-001 Pg 21 - PLC Digital Inputs.png FFSC-001 Pg 22 - PLC Digital Outputs.png FFSC-001 Pg 24 - PLC Slot 2 - 0-5 V Analog Inputs.png FFSC-001 Pg 25 - PLC Slot 3 - 4-20 mA Analog Inputs.png


Pages 40-49 are reserved for systems related to the automation system (via interconnection).

FFSC-001 Pg 40 - Boiler Auxiliary.png FFSC-001 Pg 41 - Pump House Motor.png FFSC-001 Pg 42 - Chlorinator.png FFSC-001 Pg 43 - PC2100 Auxiliary.png