Schneider Electric STO100 (EGU)
- Type: NTC 1.8 kΩ (25 °C)
- Measurement range: -50 → +50 °C
- Accuracy: ±0.4 °C (over -20 → +40 °C)
- IP: IP54
Applications
STO100 is the primary outdoor-air signal for weather compensation on Schneider Rubisafe, Rubinet, TAC Xenta and other legacy platforms (inherited after Schneider Electric acquired TAC AB in 2003). Used in substations that read NTC 1.8 kΩ. The sensor drives the flow-water setpoint calculation via the heating curve (outdoor T → flow T relationship). Delivery across the EU.
Technical specifications
| Parameter | Value |
|---|---|
| Code | 5141100000 |
| Model | Schneider STO100 (EGU series) |
| Sensor type | NTC thermistor, 1.8 kΩ (25 °C) |
| Measurement range | -50 → +50 °C |
| Accuracy | ±0.4 °C (over -20 → +40 °C) |
| Output signal | Ω (resistance) — analogue input to the Schneider controller |
| Time constant | ≈ 10 min (outdoor conditions) |
| Wiring | Terminals inside the housing, 2-wire unshielded run up to 100 m |
| Protection class | IP54 |
| Mounting | On the external wall, N/NW side, away from direct sunlight |
| Housing | White ABS plastic, UV-resistant |
| Compatibility | Schneider Rubisafe, Rubinet, TAC Xenta 100/300 and other NTC 1.8 kΩ platforms |
Designer note
STO100 uses NTC 1.8 kΩ (not 10 kΩ as Ouman). These standards are not interchangeable — do not use with controllers reading NTC 10 kΩ (Ouman) or PT1000 (Danfoss ECL, Siemens). Verify the controller documentation before replacing a sensor. Mount strictly on the N/NW facade, away from direct sun.
When to choose STO100
- Replacement outdoor sensor for legacy TAC / Schneider Rubisafe, Rubinet controllers
- New Schneider Xenta 100/300 or Rubisafe control site
- Any system where the controller reads NTC 1.8 kΩ
- Compatibility: Schneider TAC Xenta 100/300, Rubisafe, Rubinet. Not compatible with Ouman (NTC 10 kΩ), Danfoss ECL (PT1000), Siemens Climatix (LG-Ni1000).
B2B delivery and logistics
- Delivery across the EU (from warehouse in Vilnius, LT)
- Competitive B2B pricing for projects and bulk orders
- 30-day payment terms for companies (per contract)
- Free technical consultation on sensor compatibility
Manufacturer: se.com (formerly TAC AB)
FAQ
Does STO100 fit Ouman controllers?
No. STO100 is NTC 1.8 kΩ. Ouman controllers (A203, C203, EH-105) read NTC 10 kΩ — Ouman TMO/NTC10 or equivalent.
What resistance should I read at 20 °C?
At 20 °C an NTC 1.8 kΩ element reads ~2.2 kΩ; at 0 °C ≈ 5.3 kΩ; at 25 °C = 1.8 kΩ (nominal). A multimeter check is enough to confirm the element is alive.
How is the cable extended?
Standard 2-wire line up to 100 m of unshielded 2×1.5 mm² cable. Use shielded twisted pair for longer runs or high-EMI environments.
Will the system keep running if the sensor fails?
Schneider controllers usually fall back to a fixed outdoor value (often +5 °C or the last valid reading) if the sensor fails. The system stays operational but loses weather compensation — replace the sensor at the next service visit.
