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Hot-Water Heating Systems - Classification

Hot-water heating systems can be classified by temperature and pressure.

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Hot-water systems can be classified by operating temperature into three groups

  • low temperature - LTW
  • medium temperature - MTW
  • high temperature - HTW


Low Temperature Hot-Water Heating System - LTW

  • operates within a temperature of 250oF (121oC). The maximum allowable working pressure for a LTW system is usual 30 psi (2 bar).
  • LTW systems are in general used for space heating in homes, residential buildings, offices, local distribution of district heating systems and similar.

Medium Temperature Hot-Water Heating System - MTW

  • MTW systems operates at a temperature of 350oF (177oC) or less. The maximum allowable working pressure for a MTW system is usual 150 psi (10.5 bar)
  • MTW systems are often used in large hot-water distribution systems like district heating, and in systems where process applications requires higher temperatures than achievable by LTW systems

High Temperature Hot-Water Heating System - HTW

  • HTW systems operates at temperatures exceeding 350oF (177oC) or more. The maximum operating pressure for a HTW system is usual less than 300 psi (20.7 bar).
  • HTW systems are used like MTW systems in large distribution and process application systems.
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