134-1510

The Siemens ET 134 Low Temperature Detection Thermostat Series is a remote bulb instrument with a Single-Pole Double-Throw (SPDT) switch which closes and opens a circuit in both directions. This thermostat has a limited vapor charge since its liquid volume is less than the volume of 12 inches (305 mm) length of the bulb. When at least 12 inches (305mm) of the bulb is exposed to a temperature of at least 1°F (0.6°C) below the thermostat set point, the charge begins to accumulate and condense in this section. The condensing charge creates a vacuum into which the remaining charge is drawn and also condensed. When both liquid-vapor surfaces are within a 12-inch (305 mm) length, the vapor pressure in the thermal system and the bellows decrease until the electrical contacts open.