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Expansion Tanks and Commercial Hydronic Heating

Playing a vital role in any sealed water-based heating and cooling solution, expansion tanks are designed to support the changes in water pressure created by temperature changes throughout a systems day to day operation.

If you are looking to integrate hydronic heating or cooling into your next commercial heating project, expansion tanks are a necessary consideration to ensure optimal performance, safety and protection of the entire system.

But first, let’s look at what these products do and why they’re important in commercial hydronic heating and cooling solutions. In this article we’ll cover:

  • What does a hydronic expansion tank do?
  • Why are expansion tanks important?
  • Types of expansion tanks
  • A couple of considerations

expansion tank, hydronic heating parts

What Does a Hydronic Expansion Tank Do?

The Laws of physics dictate, when water heats up it expands, when water cools down it contracts, this resulting action will therefore create pressure fluctuations within any sealed system.

To actively manage this everyday occurrence, we use expansion tanks.

Why Are Expansion Tanks Important?

Expansion tanks are designed to absorb the expansion and contraction of water within sealed heating and cooling systems, throughout their normal day to day operation.

If no expansion tank were to be installed, upon temperature rise a system can increase in pressure as the water within expands, as the pressure increases at some point a safety valve will activate, releasing the system pressure. As water is safely released from the system, crucial system inhibitor is lost. Over a period of time if this were to continue, all the valuable system inhibitor can be lost, which can cause the system to rapidly deteriorate.

By installing an expansion tank you are protecting the heating system, improving the performance, and increasing the lifespan of the entire set up.

hydronic heating system, expansion tank

Types Of Expansion Tanks

Correct product selection is important to ensure you are getting the most suitable solution for your heating system. The product that best meets your system needs will be determined by the type of system you have or are planning to install, the application and the water volume.

The two main expansion tank types are:

Bladder Expansion Tanks

Within this tank is a replaceable synthetic rubber membrane, or bladder. Generally, the simple bladder expansion tank is suitable for any system, whether it be for heated or cooled water. It is also a workable option for any system running on untreated water.

The benefit of this expansion tank is that all the water is within the rubber bladder, none of it is in contact with the tank itself, which removes the risk of corrosion.

Pump Controlled Expansion Tanks

This option can regulate the incoming pressure and system expansion at the same time. The setup is similar to the bladder expansion tank, but with the addition of a pump, which controls the pressure.

The pump can add or remove air from the system as needed to ensure that there is a consistent pressure, which encourages and increases the longevity of water-based heating systems, such as hydronic heating and cooling.

Pump controlled expansion tanks are seen to be a step above the bladder expansion tank, in that the pressure control results in a more accurate calibration and a higher percentage of the tanks capacity can be used.

A Couple of Considerations

When it comes to installing your hydronic heating or cooling system, an appropriately sized expansion tank should also be installed to support the system. For sizing and selection consult with an experienced professional.

A couple of other considerations to keep in mind with your expansion tank installation:

Location, Location, Location

Firstly, aim to install an expansion tank by connecting into the return line, ideally before any pumps, this way the tank is subject to minimal pumping pressure, pro-longing the tanks life.

Also ensure that the tank does not terminate into the system at low point, where muck and/or debris can gather.

Oversized Tanks

It is worth considering an oversized expansion tank to the dimensions calculated for your system. Having a larger tank will reduce changes in the system pressure as water temperatures fluctuate.

Expansion Tank Summary

Expansion tanks are an essential component of any commercial hydronic project The appropriately selected and fitted products will ensure the safety and  ongoing use of a system, in addition to optimal performance and product longevity.

Consulting with hydronic heating professionals with experience in commercial system design and installation is’s advisable to ensure you select the best possible product to match your unique project requirements.

Hunt Heating has provided the Australian commercial market with hydronic heating and cooling solutions since 1982. We’ve designed complete heating systems for large-scale accommodation projects, office buildings and smaller commercial retail spaces.

Contact us to discuss your project requirements with an experienced commercial consultant.

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