Computer aided design in compliance with Latest European Norms. Suitable for heavy duty operation conditions, peak and fluctuating demands. Suitable for long distance central city heating systems. Maximum benefit from heating surface with Wet-Back Design Burner selection flexibility Low Thermal Inertia reduced service cost, better heat transfer in combustion chamber and Lox-Nox emissions Low firing rate, more effective use of radiation heat transfer surfaces, best combustion emissions in combustion chamber Suitable to operate with Rotary-Cup type or Pressure-Jet type burners. Up to %96 efficiency at LHV with economizer, more fuel saves. Working Principle SHW is used for producing superheated water without boiling and evaporating of water under high pressure. Combustion chamber is connected to flame-reserve chamber at the back. Combustion gasses go in to second-pass flue-gas tubes through this chamber. Flue gasses go in to front smoke box and there, they go in 3rd pass tubes. They reach to rear box the boiler after 3rd pass tubes. This kind of working principle allows to boiler to work at heavy duty operating conditions, for peak energy demands, at high inertia with all kinds of burners including Rotary-Cup type.