Water Heating Contact Thermostat Solar/Wetback 50-70C (ST13-70K)

The ST206 Contact Thermostat (ST1301133) is engineered for electric storage water heaters. It provides precise temperature control through a bi-metal disc mechanism and integrates a manual reset high-limit cut-out (OTC) for safety. Surface-mounted with quick-fit lugs, it’s easy to install and trusted by OEMs for durability and reliability.

For wet back and solar-boosted systems, the ST thermostat design also offers special over-temperature protection. Unlike standard thermostats, which trip at 80–88 °C, the solar switch technology allows the bi-metal disc to cycle during high solar gain heating without nuisance tripping. Only when an actual over-temperature fault occurs (with live power at the contacts) does the switch fully isolate both poles, in a “one-shot” action that cannot be reset, ensuring maximum protection in solar applications.

ST Thermostat Wiring Diagram

• Automatic cycling using a bi-metal disc (opens/closes on temperature rise and fall).
• Integrated high-limit OTC with manual reset for over-temperature protection.
• Solar over-temperature design: tolerates high solar gain heating cycles, avoids nuisance trips, and provides one-shot isolation if a true fault is detected.
• Surface mount with quick-fit lugs for fast installation.
• Electrical rating: 30 A @ 240 V AC.
• Equivalent to ST1301133 — suitable for OEM replacements and retrofits