Design Load With Sizing Factor

How should we use "the sizing factor"? Typically the cooling load calculated by OS is very low, is the default cooling sizing factor of 1.15 based on comparison with Trace 700?

ASHRAE appendix G says: The equipment capacities for the baseline building design shall be based on sizing runs for each orientation (per Table G3.1, No. 5a) and shall be oversized by 15% for cooling and 25% for heating, i.e., the ratio between the capacities used in the annual simulations and the capacities determined by the sizing runs shall be 1.15 for cooling and 1.25 for heating.

If you oversize more than 1.15 your chiller would work with a lower EER most of the time.

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Gio

answered 2018-02-09 04:41:16 -0500

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Thank you Gio, it makes sense. I noticed the factor can be chosen by the user of OS and when I read a few old old/conversations here I misunderstood this factor has been added to make up the difference between the calculated loads from Trace 700 and OS! I don't know if there is any update Re this difference or not!