We proposed the operating number control of hot water boiler to save the heating energy consumption in office building. First,
we split the existing boiler into two same capacity(500KW). As a result, the heating energy saving rate was 21%. And, we split
the existing boiler into two capacity of 700KW and 300KW according to the heating load. In this case, the heating energy saving
rate was 33%. These results presents the higher saving rates of heating energy consumption about 11% than that of the case of
improving the existing boiler efficiency from 80% to 90%. Therefore, it can be said that the operating number control is more
efficient way to reduce heating energy consumption than the improvement of existing boiler efficiency.