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Which cooling design day is most common for sizing rooftop units?

asked 2016-04-21 11:55:54 -0500

Rohini's avatar

updated 2017-05-08 15:44:36 -0500

The energyplus weather file has 12 design-days for cooling. One of the variables is 0.4%, 1%, and 2% - I am assuming 0.4% is the most common for hvac-sizing. Not clear on which one of the following is more common - DB=>MWB, WB=>MDB, DP=>MDB, Enth=>MDB. I am guessing DB=>MWB is most common but would like to confirm. When does it make sense to use one or the other. Does anyone use the latent load related design-days on actual projects? Thanks.

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answered 2016-04-23 11:48:59 -0500

updated 2016-04-23 21:14:41 -0500

The 2009 ASHRAE Fundamentals Handbook Chapter 14 on Climate Design Information will explain the use of these weather data and the terminology.

This document explains that the DB=>MWB is used for sizing chillers or HVAC systems (pg 14.6), WB=>MDB is used to size cooling towers, evap-coolers, and ventilation systems. The DP=>MDB data is used for sizing dehumidification systems. And finally, Enth=>MDB is used for sizing based on infiltration and/or ventilation.

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Asked: 2016-04-21 11:55:54 -0500

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Last updated: Apr 23 '16