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Jandy

Jandy JXi, JXiQ, JRT and JE Heaters and Heat Pumps

Jandy gives these heaters two ways in and colour-codes them: a red terminal bar for RS-485, a green one for a dry contact. Either way there is a setting on the heater's own panel that has to be changed, and until it is, correct wiring does nothing at all.

Choosing between the two methods

Dry contactRS-485
WherePOOL and COMMON on J6, green terminal barRed terminal bar, four-pin
ConductorsTwoTwo of four
Module outputH1 or H2 dry contactPORT A or PORT B
Heater settingRemote = T-StatSee below
What you getOn or off onlyOn, off and fault reporting

RS-485 is the one worth wiring. Jandy's own description is that the connection makes the heater and the controller “smart”, in that the control knows if the heater is malfunctioning. On a dry contact the module can ask for heat and has no way of learning that the heater locked out — the customer finds out when the water is cold.

RS-485 on the red terminal bar

PinColourPurposeiSmart Module
1RedSupply positiveNot connected
2BlackDataPORT terminal A
3YellowDataPORT terminal B
4GreenSupply commonNot connected
The red four-pin connector, same as every other Jandy device. The outer pair is supply a Jandy power centre provides; the inner pair is the data.
The Jandy four-pin connector: pin 1 red and pin 4 green are the supply pair, pins 2 black and 3 yellow are the data pair that goes to a PORT.
Inner pair to the PORT, outer pair capped on a mains-powered heater.

Dry contact at the Power Interface Board

The simpler route puts two wires on the heater's Power Interface Board at the terminals marked POOL and COMMON, on J6. Closing a contact across them calls for heat. Drive it from H1 or H2 using COM and N.O so the contact rests open and the heater cannot fire while the module is unpowered.

  1. 1

    Wire POOL and COMMON

    At the Power Interface Board, land two conductors on the POOL and COMMON terminals of J6, and take the other end to COM and N.O on a heater output.

  2. 2

    Set the heater's own thermostat to maximum

    Set the pool thermostat to 104 F. In this mode the module decides when heat is wanted, so the heater's own setpoint must not be the thing that limits it.

  3. 3

    Open the installer menu

    At the heater's user interface, hold MENU, POOL and SPA together for seven to ten seconds.

  4. 4

    Set Remote to T-Stat

    Change the Remote setting to Remote T-Stat so the heater expects a thermostat closure on J6. Press the POOL button to exit.

  5. 5

    Prove the contact

    Call for heat from the app. The heater should begin its ignition sequence within a few seconds. Drop the call and confirm it shuts down.

Installer settings that affect automation

The same hidden menu — MENU, POOL and SPA held together — carries several settings that change how the heater behaves under an external controller. These are worth checking at commissioning rather than discovering later.

SettingOptionsWhy it matters
RemoteOff / Hi-Lo-Com / Remote T-StatSelects how the heater expects to be commanded. Off ignores external control.
Maintain TempDisable / EnableEnabled, the heater works to hold temperature on its own — which competes with the module's scheduling.
Maintain Temp Delay0:00 to 2:00 hoursHow long it keeps doing so. Only relevant if Maintain Temp is enabled.
Water Temp Diff+1 to +5 degreesThe heater's own hysteresis. Set it deliberately against the module's differential so the two do not short-cycle the burner.
Freeze ProtectOff / On (34-42 degrees)Decide whether freeze protection lives here or in the module. Two independent freeze strategies is worse than one.
Water Temp CalPlus or minus 4 FCalibration offset. If the app and the heater disagree on temperature, check this before assuming a sensor fault.
From the JXi installer menu. Maintain Temp is the one most likely to surprise you.

Diagnostics on the heater itself

The installer menu also exposes a Last Fault entry and a Statistics screen showing gas valve run time in hours and the number of times the heater has fired. On a dry-contact installation these are the only fault history you get, since the contact carries no information back. Worth reading before replacing anything.

When it does not fire

SymptomWhere to look first
Contact closes, nothing happensRemote still set to Off. On this heater that is the most likely cause, ahead of any wiring check.
Fires but stops short of setpointThe heater's own thermostat was left below maximum in T-Stat mode.
Heater runs constantlyContact wired across N.C instead of N.O, or a link left on J6.
Short-cyclingWater Temp Diff fighting the module's differential, or Maintain Temp left enabled.
RS-485 wired but silentSwap black and yellow, cycle power, then confirm nothing else shares the PORT.
App and heater disagree on temperatureWater Temp Cal offset on the heater.
Fires then locks outThe heater's own flow and limit devices. Read Last Fault in the installer menu.

Sources