Check the exact module generation, signal wiring and fault indicators before replacing parts.
A qualified electrician must isolate every involved circuit before inspecting or changing wiring. Identify the thermostat, each nJoin module and supply voltage, then use the diagram for that combination.
- Check the signal chain. For the USG-4000 arrangement in the linked diagram, the output A/B of the controlling device connects to C/D of the next module: A to C and B to D. Do not confuse a thermostat’s floor-sensor input with the module signal input. For USG5-4000, use its own quick-start diagram. Incorrect primary/secondary wiring can leave a relay continuously on and overheat the floor.
- Check each module’s supply, load and GFCI. The USG5-4000 maximum resistive load is 15 A: 1,800 W at 120 V, 3,120 W at 208 V or 3,600 W at 240 V. Its signal runs are limited to 80 ft (25 m) between successive devices, with 20 AWG field wiring recommended.
- Interpret the correct generation’s indicators. On USG5-4000, white indicates power without heat demand; white while the thermostat calls for heat points to the signal connections. Amber indicates heat demand, but can remain amber during a GFCI trip even though the relay is off. Check the separate GFCI indicator.
- Verify the heating circuit separately. If the wiring and controls check out, have the electrician test the affected heating circuit against its factory ratings and installation instructions. A cable length on a plan is not a resistance measurement and cannot establish that the cable has failed.
After safe reassembly, verify that each zone responds to heat demand and turns off correctly. Contact WarmlyYours technical support at (800) 875-5285 with model numbers, diagrams and readings if results conflict.
Sources: USG-4000 wiring diagram, USG-4000 installation instructions, and USG5-4000 quick-start guide.