When you are exploring a replacement heating system or domestic hot water system for your commercial building, sports facility, or institution, you will quickly come across terms such as direct-fired boiler and indirect-fired boiler. But what do these terms actually mean? And which system is best suited for your situation? In this blog, we clearly explain the differences, the advantages and disadvantages of both systems, and when it is best to choose each type of domestic hot water system.
What is a direct-fired boiler?
A direct-fired boiler is a system in which the water is heated directly by the burner. When you turn on the tap, hot water is available immediately. There is a direct connection between the heat source (for example, gas or electricity) and the water needed for heating or domestic hot water. Examples of direct-fired boilers include instantaneous water heaters, flow-through units, or industrial hot water boilers. Direct-fired boilers are commonly used in situations with high peak demand.
What are the advantages of a direct-fired boiler?
- Rapid heating: Ideal when you need a large amount of hot water quickly.
- High water temperatures possible: Suitable for systems with a high heat demand.
- No need to heat the entire central heating system in summer: Only the water for taps is heated.
- No transfer losses: In this direct heating method, the domestic hot water is separate from the central heating system.
- Up to 10% gas savings: A direct-fired boiler can reduce your gas consumption by up to 10%.
A disadvantage of a direct-fired boiler is that it is somewhat less efficient with fluctuating heat demand. The components are also more prone to wear and tear due to the direct heat. Additionally, direct-fired boilers are less suitable for sustainable systems such as heat pumps or solar water heaters, as these systems find it more difficult to deliver high-temperature water.
What is an indirect-fired boiler?
In an indirect-fired boiler, the water is not heated directly by a burner, but through a heat exchanger. The hot water from the central heating circuit heats the domestic water via a TSA or plate heat exchanger, which has its own separate circuit. The tank itself does not contain a heating element or burner. The heat is supplied by another system, such as a boiler, heat pump, solar water heater, or district heating.
What are the advantages of an indirect-fired boiler?
- Energy-efficient and future-proof: The system can be easily connected to sustainable heat sources.
- Less wear and tear: Since the heat source does not come into direct contact with the water, the system has a longer lifespan.
- Flexible installation: An indirect system is ideal for a hybrid setup, for example in combination with a heat pump.
A disadvantage of an indirect-fired boiler is that the water heats up more slowly and the entire central heating system must be activated. Additionally, the system requires more space due to the presence of a buffer tank or storage vessel.
Which is better: a direct-fired or an indirect-fired boiler?
The choice between these systems largely depends on your situation. In general: If you need fast access to large amounts of hot water, a direct-fired system is the better choice. If you want to prioritize sustainable solutions and your hot water demand is moderate, an indirect-fired system is more suitable.
Eco Heating Systems has been using a combination of both systems for years with the unique Eco Injection System. In this system, a condensing high-efficiency boiler directly heats the tap water. The heat from the flue gas is reused by the boiler to preheat the water, effectively heating it twice. This technique allows the system to achieve an efficiency of 107%.
Would you like to know which solution is best suited for your situation?
We would be happy to visit you to advise on which system is best suited for your needs. Of course, you are also welcome to visit us at our facility. There, you can see how we manufacture our central heating and hot water boilers and explore our applications. Contact us, we look forward to welcoming you.
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