Only Some Floor-Heating Zones Heat After Replacing a Thermostat with nJoin Power Modules

After replacing an OJ thermostat that controls one or more nJoin or nJoin 2.0 power modules, the thermostat appears to heat but one or more connected floor-heating zones remain off.

De-energize and lock out every involved circuit before inspecting wiring. High-voltage testing and corrections must be performed by a qualified electrician.

Most likely cause: miswiring. Suppose a floor-heating system worked before its thermostat and/or power modules were replaced, and now some or all zones stay off. The cause is usually wiring done during the replacement, not a failed heating element. Check the wiring first, in the order below.

1. Check the low-voltage nJoin signal chain first. This is the most important check. Between the thermostat and each power module, follow polarity B to D and A to C, as the current OJ wiring diagram specifies. At the thermostat and at every module, look for swapped, loose, or unterminated signal conductors. Use the specified field wiring (20 AWG recommended). Keep each thermostat-to-module or module-to-module run within 80 ft (25 m).
2. Check circuits and load. Power modules must not be on the same circuit as the thermostat. The thermostat and each power module need their own dedicated breaker. Total load on any one device must not exceed 15 A (1,800 W at 120 V, 3,120 W at 208 V, 3,600 W at 240 V).
3. Identify every device. Confirm the thermostat model, each power-module model, and the supply voltage. Then confirm which current WarmlyYours wiring diagram applies to that combination.
4. Test the heating elements only after the wiring checks pass. For every mat, roll, or cable, record conductor resistance and insulation-to-ground results. Compare them with its factory label. A cable length stated in feet is not an ohm reading and does not establish an open conductor. Do not condemn, disconnect, or cap a zone without measurements, or because a length or plan notation was mistaken for resistance.
5. Verify operation. Restore power only after the wiring is safe. Call for heat, confirm that each module switches its assigned zone, and measure the expected load current. If a zone still fails, run the control, line-voltage, and heating-element tests separately before replacing parts.

Escalate contradictory readings, damaged conductors, ground-fault indications, or wiring that does not match the current diagram to WarmlyYours Technical Support.