Notes to Table C407.5.1(3) state that pump system power for each pumping system shall be the same as the proposed design. If the proposed design has no hot water pumps, the standard reference design pump power shall be 19 W/gpm (equal to a pump operating against a 60-foot head, 60-percent combined impeller and motor efficiency). The hot water system shall be modeled as primary only with continuous variable flow. Hot water pumps shall be modeled as riding the pump curve or with variable speed drives when required by Section C403.4.3.4.
Default hot water loops for IECC Systems in ApacheHVAC are primary-only variable flow, have a specific pump power of 19 W/gpm, and use a constant speed pump curve. When the requirement changes based on specifics in the code users will need to change the pump performance curve to variable speed using the pull-down menu in the hot water loop dialog.
