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RE: [EnergyPlus_Support] Equipment Sizing for best savings - food for thought

Dear Jean and Jeremy,

I am keenly aware that the sizing calculations and normal conservative tendencies among engineers result in oversized equipment.  I think I recall and ASHRAE Journal article citing something like 50% (!) oversizing as common.

Engineers, however, do not size chillers with EnergyPlus.  I have assumed, though, that the energy balance calculations of E+ would result in a more realistic load peak than the typical engineer?s load calculations.

Other factors that cause a typical load calculation to produce larger values are:

·         the assumption of constant internal loads (which never happens)

·         lack of a ready means to evaluate impact of slight undersizing (e.g., What is the room temperature on a design day if I select the next smaller chiller? + .1?  +.5? +5?)

·         Unreasonable safety factors in part due to the fear Jeremy mentions about defending a smaller-than-calculated chiller size (no comment needed here other than I think the lawyers inspire more fear than they merit)


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