Frequently asked questions

• Where does the WTS01 get power, and can my phone see it without a relay?

  Power (3.0–5.5 V) arrives over the RJ9 cable from a TH Elite or TH Origin relay — the probe has no battery and no radio of its own. Without the relay it neither measures nor appears in eWeLink: in the app it lives as a temperature line on the relay's card.
• Which part of the probe is actually sealed — can I sink the whole thing?

  The stainless tip is what goes into the liquid: it is built for wet environments and direct water contact. The moulded cable joint and the RJ9 plug are not sealed — keep them in the dry zone. Sonoff publishes no numeric IP code for the WTS01.
• Why doesn't the WTS01 report humidity like the THS01?

  That is deliberate specialisation: the WTS01 reads temperature only, but its sleeve survives water and +115 °C. The THS01 adds humidity yet has no declared water protection. Tank and soil — WTS01; room microclimate — THS01; they share the same host relay.
• Will the probe survive a boiler tank and heating pipes?

  Yes: the top of the range, +115 °C, clears the boiling point, so a hot-water tank and a heating flow pipe are within spec. Seat the tip in the tank's thermowell so it reads the water rather than the shell, and route the RJ9 cable out to the relay in a dry spot.
• Can the WTS01 winter in the soil or outdoors?

  The tip itself is rated to −40 °C, so frozen ground and unheated outbuildings are fine. The weak points are the joints: shield the moulded joint and the RJ9 plug from precipitation, and lay the cable before the frosts — the sheathing stiffens in the cold.
• Is there a DS18B20 inside? And what is the 2.5 mm jack version?

  Sonoff does not disclose the WTS01's sensing element — officially it lists the −40 to +115 °C range and up to ±0.5 °C accuracy. The 2.5 mm jack version is sold under the DS18B20 name for the old TH10/TH16; the RJ9 4P4C WTS01 is a different product.
• Can the TH relay switch the boiler's heating element directly off the probe?

  It depends on the load: the THR316D switches up to 16 A, the THR320D up to 20 A and adds a dry contact for a boiler. A typical 1.5–2 kW immersion element passes with margin; three-phase or larger loads go through a contactor.
• How many WTS01 probes can one relay take?

  One: the TH Elite and TH Origin have a single RJ9 sensor socket. Each measuring point — boiler, aquarium, greenhouse — gets its own relay-plus-probe pair, and the scenes between them are tied together in eWeLink.