[EnergyPlus_Support] Re: Negative Zone/Sys Sensible Load Predicted

["eplusven" <eplusven@xxxxxxxx>]

Thank you for you responses. I found some mroe infromation on this, if anyone interested, here it is for you

http://simulationresearch.lbl.gov/dirun/28sep.pdf 

ZONE CONTROLS AND THERMOSTATS
================================
Question
==========
I want to calculate "zone sensible load predicted," "zone sensible load to heating setpoint predicted," and "zone sensible load to cooling setpoint predicted" against the setpoint. I entered a value in the "zone controls and thermostats" object but the resulting value was different from the "input/output reference" statement. The "Zone sensible load predicted" results are all 0, "zone sensible load to heating setpoint predicted" results are all negative values, and "zone sensible load to cooling setpoint predicted" results are all positive values.

Answer
========
Zone sensible load predicted gives you the thermostat load. If it is zero, there is no load. The zone temperature is below the cooling setpoint and/or above the heating setpoint. This is the theromostat dead band region. The zone sensible load to heating setpoint predicted is negative because the zone temperature is above the heating setpoint. The zone sensible load to cooling setpoint predicted is positive because the zone temperature is below the cooling setpoint.
Change your thermostat setpoints and you will see that when there is a cooling load, the zone sensible load to cooling setpoint predicted will go negative when the zone temperature is above the cooling setpoint. And when there is a heating load, the zone sensible load to heating setpoint will go positive when the zone temperature is below the heating setpoint. The zone sensible load predicted should also show these same results.
If your thermostat setpoints are correct, you will have to change the zone loads. More outside air will likely cause a load in the zone for both winter and summer. Or adding equipment/lighting loads will cause a cooling load in summer (and possibly winter).



--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "James V Dirkes II, PE" <jvd2pe@...> wrote:
>
> Dear Ven,
> 
>  
> 
> I'm not sure, but I think E+ keeps track of energy using the convention that
> energy being removed from the space is a negative value.  Energy added is a
> positive value.
> 
>  
> 
> The Building Performance Team
> James V. Dirkes II, P.E., LEED AP
> 1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
> 
>  
> 
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of eplusven
> Sent: Monday, May 17, 2010 4:27 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Negative Zone/Sys Sensible Load Predicted
> 
>  
> 
>   
> 
> Hi All,
> 
> I am running a simulation for a peak summer days, My Zone/Sys Sensible Load
> Predicted output negative values like -39671 W. Can someone suggest me what
> could be the problem. My thermostat setpoint is 25C, and outside average
> temperature is above 27C.
> 
> Best Regards
> -Ven
>




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