Pool Systems Automation

As of December 2020, a project is underway to add monitoring and control automation to the pool systems.

The reasons for this 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.

Controller

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.

Monitoring

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.

Drawings