The legacy FWT-3 uses a separate relay module and temperature sensor.
The ETI Floorstat FWT-3 uses a wall-mounted electronics assembly, a separate relay module and a wired floor-temperature sensor. The attached ETI manual identifies the electronics assembly as part 18550 and the sensor as part 19272.
- The green SUPPLY indicator shows power; the yellow HEATER indicator shows a heating command.
- Turning the knob fully counterclockwise selects standby, indicated by a blinking SUPPLY light.
- Both indicators blinking continuously with no heat indicates a sensor fault in the manual’s troubleshooting table.
A replacement is not automatically a swap of the wall control alone. ETI supplied separate 120 V and 240 V relay modules rated for 25 A, and warns that the wrong relay voltage can damage components. A qualified electrician must identify the installed relay, supply, actual heating load, sensor and wiring before selecting a replacement. A new 15 A thermostat cannot directly carry a load greater than its rating; additional approved switching may be needed.
Preserve the required ground-fault protection and any floor-temperature limit. Do not switch to room-only control simply to avoid replacing an incompatible floor sensor. The attached manual does not specify a sensor resistance curve, so compatibility must be established from the exact sensor and replacement-control documentation.
Sources: attached ETI FWT-3 manual, part 18580 revision 0.0, and nSpiration 15 A wiring diagram.