SIEBE TK-4012 Pneumatic Thermostat

The TK-4012 Direct Acting Unitary Averaging Bulb Thermostat from Barber Colman (now Schneider Electric) is a pneumatic thermostat designed for proportional control of pneumatic valves and actuators to maintain the discharge temperature of reheat systems, the sampling chamber, or the return air temperature of terminal units. It senses temperature with a 3-foot capillary and an averaging bulb sized 3/32 in. in diameter and 54 in. long, delivering a direct-acting output to the control line. The cooler-warner dial is specified for 60–90 °F, with an adjustable throttling range of 2–10 °F per 10 psi (69 kPa) supply; the factory setting is typically 4 °F. This model is part of Schneider Electric’s TK-4000 family of unitary averaging bulb thermostats and is suitable for precise, proportional temperature control in heating, cooling, or mixed-mode HVAC applications that rely on pneumatic controls.