Re: [EnergyPlus_Support] Dual Setpoint w/ Deadband and VAV boxes w/ reheat coil

["Michael J. Witte" <mjwitte@xxxxxxxx>]

EnergyPlus controls rely on the load determined by the thermostat.  If the 
thermostat calls for cooling, the VAV/reheat unit will try to provide that 
load.  If that means adding reheat to match the requested cooling load, then it 
will do so.  The terminal unit at that point is not aware of what the zone 
thermostat setpoints are, it just knows there is a call for cooling.  So, I do 
not think you have an error.  You can minimize this by resetting the cold deck 
temperature.  

Mike


On 29 Mar 2004, at 22:00, mikemccarty79 wrote:

> Hi, I am working on a simulation with VAV boxes with electric reheat 
> coils and have a controller with a dual setpoint.  My setpoints are 
> 22.2 and 22.8°C for heating and cooling respectively.  I have 
> noticed that the reheat coil will turn on but the room temperature 
> will still be maintained at the cooling setpoint of 22.8°C.  It 
> seems that since heat is being added that this should automatically 
> go to the lower heating setpoint temperature even if the zone still 
> requires some cooling.  Since the damper position is already in its 
> minimum position, I don't really need all the cooling available by 
> my supply air temperature of 15°C.  What appears to be happening is 
> that the switch to the lower heating setpoint occurs when the 
> discharge temperature from the VAV box is above the room temperature 
> or at least the cooling setpoint temperature.  Is there some error 
> in the control scheme for this or is it possible something is set up 
> wrong in my simulation.  Thanks.
> 
> Mike McCarty
> Iowa State University
> 
> 
> 
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx



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