Designed for continuous operation. They are for heavy duty laboratory service, carbon and high chrome heat-treating, etc. Split door design minimizes heat loss and aids in viewing contents. Heating elements are embedded in special refractory cement for maximum heat transfer and mechanical strength. Heating elements on four sides for minimum temperature gradient. Door safety switch removes power to heating elements when door is opened. Not supplied with cord or plug, connect through conduit connector. Controller not included. Order Furnitrol controller separately. See 36427 series. All units operate on 220V, 50/60Hz. 1730 series are rated at 5800 W. 1740 series are rated at 7900 W.