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Component Loads Summary

asked 2021-02-08 20:17:22 -0600

KAZ gravatar image

updated 2021-02-09 09:07:56 -0600


I am doing the heat and cool load calculation. The tools we are using are Energy Plus and Open Studio.

I know that if I check the Table, I can see the calculated value of the peak and Estimated Instant + Delayed Sensible Load.

In my calculation results, there is a large difference in "Difference Between Peak and Estimated Sensible Load".

I checked the manual, but I think it only explains the principle.

Is the "Zone Component Load Summary" the result of the .ddy calculation? Or is it the extracted result of the .epw calculation?

Please let me know.

Thank you.

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answered 2021-02-10 11:58:31 -0600

A heating and cooling design load calculation for the purposes of mechanical design is only interested in the TOTAL design heating or cooling load in the zone. You'll find these in the "HVAC Sizing Summary" and "Equipment Summary" reports in the EnergyPlus output report, modified by sizing factors, etc.

The Zone Component Load Summary is something quite different - it is trying to estimate the component loads that contribute to the total load, broken out by envelope loads, internal gains, etc. In the reference you cited, it explains the process for doing so, which is adding a small pulse of radiant load at 10am and comparing the zone design load with and without that pulse. The difference is used to estimate the time delay in which radiant loads are eventually convected into the zone, adding to the zone air. The "Difference Between Peak and Estimated Sensible Load" is the difference between the actual sensible design load from the zone air balance, and the estimated peak sensible load, calculated by multiplying envelope and internal loads by the time delay fractions calculated using the pulse technique. If you are seeing a large difference, it means that pulse technique wasn't great at capturing the time when radiant loads were eventually convected into the air and reflected in the zone air balance.

The Zone Component Load summary should only be used as a rough guide to determine where to focus on what envelope and internal gain components to focus on to reduce design load (quite useful for design IMO). It is calculated using the zone sizing criteria in a design day run. It should not be used to size equipment or report design load.

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Asked: 2021-02-08 20:17:22 -0600

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Last updated: Feb 10