Pool Systems Automation

Overview

A monitoring and control automation system was installed in the pump house during the 2020-2021 off-season. As of June 2021, continued refinement is still on-going. It was custom designed and installed to aide in the management of the pool, ensuring the pool is safe and comfortable for all occupants while reducing effort for the staff.

Background

The project was officially kicked off in December 2020 with the following goals:

To alert 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 drove 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.

Operation

Monitoring

Control

User Interfaces

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.

LCD/Keypad

Remote Monitoring (Dashboard)

Design

Programmable Logic Controller (PLC)

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.

Expansion Modules

Slot	Part Number	Function	Purpose
1	D0-07CDR	4 x 12/24 VDC Input, 3 x Relay	Not used at this time (spare)
2	F0-04AD-2	4 x Analog Input (0-5 VDC or 0-10 VDC)	Sensor inputs (pressure)
3	F0-04AD-1	4 x Analog Input (0-20 mA or 4-20 mA)	Sensor inputs (flow, depth)
4	N/A	Not Populated	Spare

Serial Interfaces

The DL06 PLC has two serial interfaces. On this unit, they are configured as follows:

Serial Interface	Electrical Configuration	Serial Configuration	Purpose
Port 1	RS-232	9600 8O1/None	Programming
Port 2	RS-232	38400 8N1/None	Modbus Polling

Sensors

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, ORP probe and conductivity sensor. These sensors are fed into the Chemtrol PC2100 and are detailed here.

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 P51530-P1	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

NOTE: The flow meter was previously a GF Signet MK515.3P1. Erratic behavior prompted its replacement in early June 2021.

Drawings

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.