Boilers and Hot Water Heaters Heat is usually supplied by heating boilers, and hot water by large water heater systems. Some manufacturers use process steam supplied by high-pressure boilers. Many close-tolerance manufacturing processes require complex systems to maintain stringent control of temperatures. The expensive boilers and pressure vessels that generate and distribute heat and hot water are vulnerable to breakdown due to excessive internal scale or failure of low water cut off controls. Boiler breakdown can also result in business interruption loss. © 2004 The Hartford Steam Boiler Insurance and Inspection Company.     All rights reserved.