Roughly calculate the design for the heating expansion tank

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As soon as you install a new heating system in your house, you also have to calculate the design of the expansion tank. To do this, you need some important data about the heating system. Then the calculation is actually not a big problem.

Since the water expands in the boiler and radiators due to heating, an expansion tank must be installed so that the water pressure does not become too high. You must determine the design of such a container beforehand.

The expansion vessel must be the right size

In order to be able to determine the design of the expansion vessel, you need to know some data about the heating system. You need to know how much water there is in the entire heating system. You also need to know the highest possible water temperature and the minimum water pressure of the system.

  • Information on the water content of the boiler can be found in the operating instructions for your heater. To do this, you still have to add the water content of the radiators.
  • To determine the content of the radiators, you can assume that an average of 10 liters of water per kilowatt of heating capacity are required.
  • You also need to know what the temperature can be in the boiler. Most oil and gas heating systems have a maximum temperature of around 110 degrees Celsius. At this temperature the volume of the water increases by about 5%.
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This is how you determine the design of the expansion tank

An example follows so that you can roughly imagine how the design of the expansion vessel is calculated.

  • If the boiler in your system has a capacity of 30 liters and a heating output of 18 kW, this means that there are around 210 liters of water in the entire heating system.
  • Assuming a maximum temperature of 110 degrees Celsius, you have to calculate as follows: 5 x 210/100. The result in this case is 10.5. The calculation means that 210 liters can expand by 5% or 10.5 liters. The expansion tank should therefore have a volume of at least 10.5 liters. In case of doubt, for safety reasons, it is better to install a somewhat larger container that holds 15 liters, for example.

It is therefore quite easy to roughly determine the design of the expansion vessel. No special subject-specific knowledge is required for this.

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