Standard heaters are available in 120, 208 and 240 volts. Heaters with two elements are designed for single-phase operation, while three element heaters can also be used for single-phase applications where space limitations preclude the use of a two-element heater.
Since standard heaters are made only with copper elements, their use is confined to water or solutions not corrosive to copper or brass. All heaters are designed at a watt density of 50 watts per square inch or less.
UL Listing - All standard Bottom-Mounted immersion heaters, with or without a low water cutout, are Listed by the Underwriters Laboratories under Reference E23541.