The 20T-300-4-1/2 is a 2" Temperature Swichgage. This very popular design features a diaphragm-actuated, temperature-indicating gauge, with a built-in electrical switch for tripping alarms and/or shutdown devices. This model has a 4 foot capillary length with a standard 1/2-14 NPT threading, and a temperature range from 140-300°F (60-149°C).
The gauge mechanism is enclosed in a steel case coated to resist corrosion. A polycarbonate, break-resistant lens and a polished, stainless steel bezel help protect this rugged, built-to-last instrument. This vapour actuated gauge features a sealed capillary tube and a sensing bulb. When subjected to heat, the liquid in the sensing bulb changes to vapour creating pressure against the diaphragm mechanism. The diaphragm translates this vapour pressure into a mechanical gauge reading.
Inside the 20T-300-4-1/2, the gauge pointer acts as a temperature indicator and as one switch pole which completes a circuit when it touches the adjustable limit contact. Contact(s) are grounded through the Swichgage? case. This gauge has a self-cleaning motion to enhance electrical continuity.