Zhermack furnace blends the benefits of pipe heating with electronic essentials. The pipe heating system is more efficient than a muffle system and even more efficient with a chamber. It’s more dependable over the long-term. Comes with a 1 year guarantee. The resistors are located inside the refractor pipes. An electronic switch senses the hatch opening and intercepts the resistors power supply. Electronic microprocessor controls the temperature, speed the temperature increases at and maintenance time. Uses minimum energy. This furnace good choice for quick investment needs. Can be purchased with optional aspirator OFF temp available.