Introduction

• Hot water boilers, or hydronic boilers, form the most important part of a heating system in homes, buildings and industries. The boiler works by applying heat to water. The fuel used is natural gas, propane or electricity. Hot water boilers are available as small portable units and large units used to heat buildings and for industrial use. Water boilers are expensive to install. The advantages of water boilers are that they last longer and give fewer problems than other types of heating systems.
  
  

Components

• The components that make up a water boiler are the thermostat to regulate the heat, the gas valve, a pressure gauge to monitor the water pressure, a water feed valve, a pressure-reducing valve, an air vent to draw out unwanted air, an expansion tank to allow water to expand when heated, a flow control valve that regulates the flow of water, a pressure relief valve, a circulator (an electric pump that helps to circulate the water) and a drain valve.
  
  

Types

• There are two basic types of hot water boilers: the fire tube and water tube. The fire tube boiler is also called the shell type. Hot gases go through the interior of the tube and heat water. In the water tube type of boiler, heat is applied around the exterior of the water container to heat the water within.
  
  

Systems

• There are four hot water boiler systems. The closed system reuses 100 percent of the water that evaporates after heating. The evaporated water cools and is heated again in the boiler. The open system heats water, but the evaporated water isn't reused. The single-pipe system uses two pipes. One pipe takes the hot water to the area that requires heating; the other pipe brings back the cool water to the boiler with the help of an electric pump. Older hot water boilers use a gravity system by which water is transported after heating through gravity. They don't use circulators.
  
  

Process

• The fuel is supplied to the pressurized tank of a boiler. The temperature of the fuel is regulated by the thermostat. The water is mixed with a controlled amount of air in the pressurized tank. This causes the fuel to burn. The burning fuel is sent through a pipe to the cylinder where water is stored. The fire is applied to the water and starts heating the water. The hot water is pumped by a circulator through another pipe to the areas of the building that require the heat.
  
  

Maintenance

• A water boiler requires regular maintenance. If the boiler bursts because of poor maintenance, it could cause fires or explosions. The cylinder should be drained periodically and cleaned. This is because pipes could get clogged with mineral buildup from nitrates in the water. Oil should be applied to the pipes to keep them well lubricated. The pipes should be periodically checked for leaks. The pressure gauge should be carefully monitored for any abnormality in pressure. The boiler should be periodically inspected and certified by an expert. .