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Negative load values

asked 2015-05-07 20:10:51 -0500

hugopft's avatar

updated 2015-05-08 06:09:09 -0500

I am doing the simulation and as a result of some zones I am getting negative values ​​in the ZONE REPORTING . These negative values ​​appears in the SENSIBLE-DELAYED column . Besides the negative values ​, often this column presents very big values ​​. Is It Normal? Am I missing something ? If it is normal what is the reason for that , I mean the big and negative values ​​?

Another question is: Why this reporting has a row for the infiltration and ventilation load and it does not show these values?

The figures below show my concerns.

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Which version of EnergyPlus are you using?

pflaumingo's avatar pflaumingo  ( 2015-05-07 21:13:43 -0500 )edit


hugopft's avatar hugopft  ( 2015-05-10 17:13:48 -0500 )edit

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answered 2015-05-08 06:31:42 -0500

The Zone Component Loads Summary report uses a side calculation to try to estimate the impact of various components of the load based on estimated "decay curves" for the zone in question. I would recommend you look in the Engineering Reference to see more detail about how the calculations are performed. For the results you are showing, I would say that the decay curve calculation was probably very poor. If you look at the corresponding "Cooling Peak Conditions" table you will probably see that the Peak Design Sensible Load is far from the Estimated Instant + Delayed Sensible. This would indicate that the overall estimate was poor and should not be used. The description from the Input Output Reference says:

The Zone Component Loads Summary provides an estimate of the heating and cooling peak loads for each zone broken down into various components. This report may help determine which components of the load have the largest impact for the heating and cooling peak design conditions. When specified, the Zone Component Loads Summary report is created for each zone that is conditioned. The Sensible-Delayed column of the summary is only an estimate based on a procedure described in the Engineering Reference documentation. An intermediate calculation in this procedure is the decay curves that are shown in the the EIO file when Output:Surfaces:List is set to show DecayCurvesFromZoneComponentLoads. The difference between the peak design sensible load and the estimated instant + delayed sensible load (as shown in the Peak Conditions subtable) is an indication of how consistent the overall total estimate may be to the computed total peak loads for the zone. When the report is called the zone sizing calculations are repeated twice so this may result in longer simulation times. The key used to obtain this report is ZoneComponentLoadSummary.

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Ok, but, do you have any clue why this value is negative and why the ventilation and infiltration loads are not reported in this zone summary?

hugopft's avatar hugopft  ( 2015-05-10 17:41:21 -0500 )edit

Sorry, it is impossible to diagnose the problem from just that table. You might want to submit a help request to the EnergyPlus helpdesk.

JasonGlazer's avatar JasonGlazer  ( 2015-05-11 05:54:18 -0500 )edit

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Asked: 2015-05-07 20:10:51 -0500

Seen: 676 times

Last updated: May 08 '15