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

Jandy Heater

Wiring Connections

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Pool/Off/Spa Connector

Connecting to a Remote Pool-Off-Spa Selector (3-Wire Connection) (See b above)

• Turn off the power to both the pool/spa control system and the heater unit.
• Follow service access instructions from Section 6.1.
• Run the wires from the pool/spa control system through the low voltage knockout on the right or left hand side of the heater.
• Connect the wiring from the pool/spa control system to the heater remote control terminal. See Figure 16 item “b”.
• Connect the three wires to the Spa, Pool & Common terminals of the J6 terminal bar.
• Reinstall front panel.
• Restore power to the heater and the pool/spa control system.

NOTE: When a fireman’s switch is being utilized and “hi-lo-com” is selected, the heater will fire automatically when the contacts close even if the user interface on the heater is off.

Configure the Control Panel

• Make sure the pool heater is OFF.
• Press and hold MENU, then the POOL and SPA buttons for 5 seconds to access Service Setup mode.

NOTE: The display will revert back to OFF 1 minute after the last key press.

• Press Up or Down to display REMOTE.
• Press MENU, REMOTE OFF (default) is displayed.
• Use Up or Down to scroll through the Remote options until HI-LO-COM is displayed, then press MENU to select.
• Press POOL or SPA to exit Service Setup mode

Adding Temperature Probe to Heater

If we want to add a temperature sensor to the heater, we can add one to the outlet (see f in diagram below). 

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Would add it to "f" - M 3/4" NPT

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RS-485 Interface

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RS485 protocol, wiring & adapters

All pool equipment uses a half duplex RS485 protocol to comunicate between Control Panel, Keypads and inteligent Devices like Salt Water Generators, Variable Speed Pumps, Chemical feeders & some heaters.

There are a few main problems areas that you should have a basic understanding of, that can effect the performance.

• RS485 Wiring and Termination (The majority of issues new people have are here)

• RS485 USB Adapters and how they actually work in reguard to Pool equiptment. (this becomes very important on busy RS485 bus)

Wiring and Termination

Below is a basic diagram of an RS485 bus

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As you can see, each device is connected to 3 wires (Data+, Data- & Ground), and there is a termination resistor at each end of the wiring (or bus).
The ground connection is their so the adapter has a referance point for the voltages in Data+ & Data-, and there is some level of circuit protection.
The termination resistors are their to prodide clear signals and stop reflection. Here is a detailed article on that

Protocol

See:

http://doityourselfchristmas.com/forums/archive/index.php/t-14596.html?s=ae1a73bb141ff476470ef72d8725fe06

http://doityourselfchristmas.com/forums/showthread.php?14596-USB-to-RS-485-used-to-reverse-engineer-something&s=4c54477f671a75a57ae844bbc5424268

Table 1 of the manual you posted lists the connections as
Red: +10V
Black: SD+
Yellow: SD-
Green: GND

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Notes

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Pool/Off/Spa Solutions

Micro Controller

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