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5 Tips For Using A Tankless Water Heater For Underfloor Heating

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Traditionally, underfloor radiant heating systems utilized water heaters with storage tanks. The water was heated in the tank and then pumped throughout the home. However, now more people are utilizing tankless water heaters for their underfloor heating. In these systems, the water is stored in the system and pumped directly through the water heater and back into the system, cutting down on heat loss during storage. 

One benefit of tankless water heater underfloor systems is that they tend to work well as an open loop, meaning that the same water that is used to heat your home will eventually be used at your taps and replaced with fresh water. This allows you to save space and energy, using one water heater for all of your needs. However, to successfully make and use an open loop tankless system, there are a few things you should keep in mind. 

Do Not Use Antifreeze In An Open Loop System

Antifreeze can be a good addition to a closed loop system. It prevents water from freezing and causing cracking in your pipes when your system is not in use. It also has lower energy requirements to raise the temperature, which can save you money. However, in an open loop system, your heating water will combine with your drinking and bathing water. For this reason, it is important to never add antifreeze to an open loop system. Additionally, you should make sure that you use potable grade parts throughout the entirety of your system. 

Choose the Correct Tankless Water Heater For the Job 

As your water cycles through your heating system and back to the water heater, it will typically be warmer than the water that comes directly out of your tap into the heating system. This can cause your water heater to cycle on and off, putting undue strain on the heater and causing it to fail sooner than expected. To prevent this, it is important to choose a unit that offers variable speed heating and is able to maintain a low speed for extended times without turning off. It is also important to purchase a water heater that has the capacity to heat your home and the water you consume. 

In Open Loop Systems, Keep the Water Above 140 Degrees Fahrenheit 

One of the main benefits of tankless water heaters is that you generally do not have to worry about legionella, since the water is not stored. However, if you have an open loop system, the water is stored briefly in your heating system. Therefore it is important that you set your water heater to a temperature that will kill the legionella bacteria. 140 degrees Fahrenheit is the recommended temperature. 

Turn Off the Pump On an Open System for Free Cooling During the Summer 

During the summer, when you are not heating the water in your heating system, it can be used to help cool your home. The water heater will draw the water from your heating system when you use hot water within your home. This allows the cold water to collect heat from your home, making the water heater work less to heat the water and cooling your home at the same time. 

Be Aware That Water May Taste Like Plastic In the Beginning 

If you have a PEX system, it is possible for your drinking water to develop a slight plastic taste when you first install your system. As long as you select drinking-grade PEX, this should not be a problem and the taste should fade with use

If you are considering underfloor heating, a tankless water heater should be one of your first choices for heating the water in your system. For more information, visit websites like