The HBB Series Heaters are ideal for new home construction, remodeling or room additions. Clean, quiet, comfortable heat, when and where it's needed. A sheathed electric heating element is totally immersed in a heat-transfer liquid and sealed in a heater-length copper tube. The large diameter reservoir maximizes the volume of heat storage fluid to prolong the thermal constant of the entire heater. Gentle heat keeps radiating even after the thermostat turns off because of the hydronic elements retention qualities.