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Common Boiler Problems: The Expansion Vessel

A combination boiler directly supplies the central heating and the hot water. Although the boiler supplies both the heat and hot water, it will provide hot water before heat. For example, if you attempt to get hot water, the heating will shut off while the water is being heated. In most situations, problems with gas-combination boilers can be avoided with routine maintenance. But, like with many other heating sources, many people do not think about potential problems until the heat stops working. The most common reason for boiler repair with a combination boiler is the expansion vessel.

What Is an Expansion Vessel?

The expansion vessel, also known as an expansion tank, is used in the boiler to absorb the excess pressure. Basically, the expansion vessel uses either air or nitrogen as a charge to ensure there is a steady amount of pressure for the water inside the boiler because it expands as it is being heated up. After reaching a certain amount of pressure, a valve opens and releases the water. As the expansion vessel ages, it begins to lose the charge from the nitrogen or air and will need to be reset.

What Are the Signs of an Expansion-Vessel Problem?

One of the first signs that will alert you of a problem with the expansion vessel is an increased reading of the pressure gauge. Most gauges will have a reading of one when the system is cold and rise to a reading of about two when the water begins to heat up. If the pressure gauge has a reading of three or more, you should have a boiler-repair company do an inspection to check for a problem with the expansion vessel. Other signs of a problem with the expansion vessel may include:

  • Dripping water from the overflow pipe
  • Longer time for water to heat up
  • Less hot water than you typically have
  • Reduced water pressure
  • Pressure gauge going up then suddenly dropping
  • Central heating system is maintaining the temperature you set
  • Boiler makes a hissing or clicking sound

In many situations, the expansion valve will simply need to be reset. However, if you do not the repairs as soon as possible, it can cause further damage, and instead of having minor boiler repair, you may have to replace the entire boiler. The best way to avoid the risk of being without hot water or heat is to have scheduled routine maintenance and inspections for the boiler system.

Talk to a company such as Robinson Heating & Cooling Inc to learn more.