Overview

The objective of this project is to control the Jandy pool heater. We can either control the heater using it's REMOTE relays or interface with it's RS485 interface.

The equipment we will to interfacing with is the Jandy JXi Gas-Fired Pool and Spa Heater 260N.

Micro Controller

For this solution, we are using a Sonoff SV controller. This is a nice controller since it has everything we need to control the heater's remote relays. Additionally, we can power it from the heater itself since it accepts 5-24 volts input and the heater will supply us with 10v. We are going to use the Sonoff SV in isolation mode by removing the two resisters that would normally supply the power to the controller using the input voltage.

Wiring

Wiring Diagram

Wiring Pictures

Temperature Sensor

We are going to add a temperature sensor to the heater so that we can turn the heater on or off based on temperature.

We are going to use

• Waterproof Digital Temperature Temp Sensor Probe DS18b20
• a 1/4″ MIP to 1/4" compression adaptor
• 2x 1/4" o-rings
• teflon tape

For the 1/4" adaptor, some adjustments were needed.

We needed to

• drill out a metal piece on the compression cap in order to get the temperature probe through.
• drill out the body of the adaptor

Once the drilling was done, we were able to pass the thermometer through the adaptor.

We added 2 x 1/4" o-rings for sealing the compression fitting to the temperature probe.

We can add a temperature sensor to the heater's header using the following procedure:

• Turn off the power to the heater
• Remove drain plug from header and allow all water to drain from heat exchanger.

• Locate the threaded port on the inlet side of the header, and find the dimple at the center.

• Use the dimple to center the drill bit. Drill a 1/4 in (6.4 mm) diameter hole through the port. Take care not to damage the plastic threads. TIP: Drilling a 1/8 in (3 mm) diameter hole first will help prevent thread damage
• Wrapped 5-6 turns of PTFE (Teflon) tape around the male threads of the adaptor.
• Thread in your 1/4 inch adaptor into the port. Make sure to get a snug fit. Do not over-tighten.

Firmware

We used custom firmware for our solution.

... more to come... 

The custom firmware has a MQTT configuration allowing it to integrate with homebridge.

Homebridge Configuration

Using the mqtt-thing homebridge plugin, add the following configuration:

{
            "accessory": "mqttthing",
            "type": "thermostat",
            "name": "pool-heater",
            "url": "http://192.168.1.50:1883",
            "username": "homebridge",
            "password": "pass",
            "topics":
            {
                "getCurrentTemperature": {
                    "topic": "pool-heater/status",
                    "apply": "return JSON.parse(message).temperature_f;"
                },
                "getTargetTemperature":{
                    "topic": "pool-heater/status",
                    "apply": "return JSON.parse(message).tarTemperature_f;"
                },
                "getTemperatureDisplayUnits":{
                    "topic": "pool-heater/status",
                    "apply": "return 0;"
                },
                "getCurrentHeatingCoolingState":{
                    "topic": "pool-heater/status",
                    "apply": "return JSON.parse(message).state;"
                },
                "getTargetHeatingCoolingState":{
                    "topic": "pool-heater/status",
                    "apply": "return JSON.parse(message).mode;"
                },
                "setTargetTemperature": {
                    "topic": "pool-heater/command",
                    "apply": "return 'setTemp ' + message;"
                },
                "setTargetHeatingCoolingState": {
                    "topic": "pool-heater/command",
                    "apply": "return 'mode ' + message;"
                },
                "setTemperatureDisplayUnits": {
                    "topic": "pool-heater/command",
                    "apply": "return 'tempUnits ' + message;"
                }
            },
            "heatingCoolingStateValues": ["0","1"],
            "temperatureDisplayUnitsValues": [0,1],
            "minTemperature": 60,
            "maxTemperature": 100
},

In the Apple Home App we now have access to our pool heater.

References