Choosing the right expansion vessel is essential for the efficient and safe operation of any heating or water supply system. Although often overlooked, it plays a vital role in pressure regulation and in protecting components like the boiler, pump, or piping network from damage. In this guide, we break down the key differences between heating and potable water expansion vessels, and help you select the right one for your system based on factors such as boiler output, operating pressure, and water volume.
The expansion vessel for heating or water supply is gaining more and more consumers, as until recently, only a few truly appreciated its necessity. Nowadays, consumers are better informed, and through various technical issues in their plumbing systems or boilers, they have come to understand how essential the expansion vessel is for smooth system operation.
These vessels are made of special steel alloy for high corrosion resistance, and are coated with epoxy paint to protect against rust and harsh weather conditions.
Expansion vessels are divided into two main categories: heating expansion vessels and potable water expansion vessels.
All liquids and gases expand when heated and contract when cooled. In a heating system, the water that circulates continuously heats up and cools down, which naturally leads to constant expansion and contraction. When the burner (whether oil, gas, or wood) is activated, the temperature of the water begins to rise, causing it to gradually expand.
As water expands, its volume increases in liters. If this extra volume is not stored somewhere, it will cause the pressure in the system to rise to dangerous levels. This is exactly where the expansion vessel comes in. Its role is to absorb and store the excess water volume caused by expansion, preventing overpressure and ensuring system safety.
In heating expansion vessels, the water entering the vessel surrounds and compresses the internal membrane, much like an accordion. The water inlet pipe connected to the vessel must be equal to or larger than the thread size of the expansion vessel.
To calculate the required vessel volume in liters, we need to know the boiler’s thermal output in kilocalories. The general rule is: 1,000 kcal corresponds to 1 liter of expansion vessel (e.g., 50,000 kcal = 50-liter expansion vessel). It is always recommended to install a slightly larger vessel, as this can only be beneficial for the system’s performance and safety.
Potable water expansion vessels are used in domestic water supply networks, pumps, pressure booster systems, etc. In these vessels, the water enters directly into the membrane and is stored there, remaining completely isolated from the metallic parts of the vessel. This design ensures a trouble-free water system. These vessels are suitable for drinking water.
At Allwater, you will find a complete range of expansion vessels for all types of applications, manufactured with high-quality standards in collaboration with leading European factories.
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