The RAK-TR.1000B-H (S55700-P111) is an electromechanical SPDT capillary thermostat built into a wall-mountable housing. It combines a liquid expansion sensor element with a fail-safe capillary to provide reliable two-position on/off temperature limitation from 15 to 95 °C, with a fixed switching differential of 6 K.

How It Works – Liquid Expansion & Fail-Safe Capillary

• Principle: A fluid-filled capillary and sensor bulb detect temperature changes. As the fluid expands, it mechanically actuates a single-pole changeover (SPDT) microswitch without requiring external power.
• Fail-Safe: If the measuring system develops a leak, the controller permanently interrupts the circuit and prevents reconnection—a mandatory safety feature for boiler and heating system protection.
• Output: The SPDT contact allows either normally-open (contact 1-2) or normally-closed (contact 1-3) wiring, giving system designers flexibility in how the limit action is integrated into the safety loop.

Technical Specifications

• Temperature Setting Range: 15 to 95 °C, adjusted via external knob.
• Switching Differential: 6 K (±3 K tolerance from calibration point 80 °C).
• Switch Rating: Contact 1-2 (NO): 16(2.5) A, 250 V AC (DIN 3440). Contact 1-3 (NC): 6(2.5) A, 250 V AC.
• Ambient Operating Temperature: -25 to +70 °C (housing), +125 °C max. at socket.
• Standards: DIN EN 14597 for time constant, EN 60730 for pollution class.

Installation & Setup

• Protection Pocket: Includes a 100 mm G ½'' stainless steel protection pocket (PN 10) for direct pipe immersion.
• Capillary: 700 mm length, secured with a clamp-on band for surface mounting on pipes.
• Terminals: Push-in terminals eliminate screwdrivers—solid or stranded conductors up to 2.5 mm² are accepted.
• Mounting: Wall-mount via base plate, or pipe-mount using the clamp band supplied. Protection class IP43 for indoor wet/dusty plant conditions.

Applications

• Boiler temperature supervision and safety cut-out
• Heating system flow/return temperature limitation
• HVAC equipment requiring a non-electronic fail-safe thermostat