Restaurants and institutions commonly hold and serve hot foods from electrically operated countertop food warmers. Water is usually, but not necessarily, used in the wells of the warmer to act as a heat transfer medium and to improve thermal efficiency. These warmers are designed to hold 12".times.20" steamtable pans or combinations of fractionally sized pans in various depths. With the use of an adaptor plate formed from a sheet of metal with one or more openings. These warmers may also be used to hold a variety of round-shouldered vegetable pans or inserts. The rectangular vegetable pans or inserts are supported by a lip which extends outwardly at the top of the pan and rests on the top edge of the warmer well. In addition to support, the lip acts as a loose seal to prevent the escape of large amounts of steam from the area between the bottom of the well and the bottom of the pan. Like the rectangular pans, the adaptor plates also have lips and flanges to provide support and act as a steam seal.
In existing food warmers, the arrangement is as follows. A food warming insert, pan or vessel occupies the innermost position for the purpose of holding food. Just outside of the insert or pan is a metal well in which the pan is supported, and it is outside this well that an electric heating element is located. An electric band heater is often secured against the outside surface of the well to keep the food contained in the vessel at the desired temperature. In other designs, an electric heating element is spaced a short distance below or to the side of the vessel. A housing containing insulation usually surrounds the heating element. A major shortcoming of this arrangement is the heat loss resulting from having to force the heat through the well, then through the pan into the food. A general objective of the present invention is to find a way of placing the electric heating element inside the well and for efficiently transferring heat to the food containment vessel or pan in three ways; namely, by conduction, convection and radiation to thereby improve thermal efficiency of the food warmer and save energy.