Hot water boilers can be classified in several ways. Let me summarize them for you:
Classification by Operating Pressure and Temperature
According to ASME standards, they are mainly divided into three categories:
High-Temperature Hot Water Boilers (HTHW): Temperatures exceeding 250°F (approximately 121°C), pressures typically below 300 PSIG, suitable for large-scale district heating or industrial processes.
Medium-Temperature Hot Water Boilers (MTHW): Temperatures and pressures between high and low temperatures, widely used.
Low-Temperature Hot Water Boilers (LTHW): Lower temperatures, commonly used for comfort heating, such as underfloor heating.
Classification by Structural Principle
Fire-Tube Boilers: Flue gas flows inside the tubes, water flows outside; simple structure, suitable for small to medium-sized heating systems.
Water-Tube Boilers: Water flows inside the tubes, flue gas flows outside; suitable for high-pressure, large-capacity applications.
Classification by Fuel Type
Gas-fired boilers: Use natural gas or liquefied petroleum gas (LPG) as fuel; most common.
Oil-fired boilers: Use diesel or heavy oil as fuel.
Coal-fired boilers: Use coal or pulverized coal as fuel.
Biomass boilers: Use wood, straw, etc. as fuel; environmentally friendly.
Electric hot water boilers: Fully electrically powered; no direct emissions.
