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[EnergyPlus_Support] Re: VAV Boxes

Mike,

Do you think this 'oscillation' with each timestep will produce an 
average heating energy input to the zone over, say, a one hour period 
sufficient to  maintain the space at close to the heating setpoint?  
Is the effect therefore similar to a thermostat with slow reactions?

I think the version 1.3.0 modelling is probably still more realistic 
than earlier versions in terms of reheat assessment but would be 
interested in your views.

Jeff

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
<mjwitte@...> wrote:
>
> After some digging, we have verified that there is a problem with 
the behavior 
> of the reheat controls in version 1.3.0 under certain conditions.  
Without 
> getting into too much detail, if the zone thermostat predicts that 
the zone 
> would be in the deadband (between the heating and cooling setpoint) 
with no 
> HVAC operation, it sets a "deadband" flag.  When the deadband flag 
is active, 
> the reheat coil will not operate.  If the min flow of cold air from 
the VAV 
> terminal unit cools the zone below the heating setpoint, the reheat 
coil will 
> not come on until the next time step.  The solution is oscillating 
between 
> these states.  I do not know of a workaround to get this to behave 
any better 
> in 1.3.0.018.
> 
> Mike
> 
> 
> On 15 Jun 2006 at 11:33, Peter G Loutzenhiser wrote:
> 
> > 
> > >Hello All,
> > 
> > 
> > I have just started using the 1.3 version of 
> > EnergyPlus with a VAV reheat system and a dual 
> > heating/cooling setpoint temperature.  I have 
> > 13.6°C air entering the coil and I have a heating 
> > setpoint of 22°C.  I have given the reheat coils 
> > plenty of capacity and yet I still get zone 
> > temperature below the heating setpoint (in the range of 21.7°C).  
Why is
> > this?
> > 
> > Peter
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> > 
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> > 
> > Attachments are not allowed -- please post any files to the 
appropriate folder
> > in the Files area of the Support Web Site.
> > 
> > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.idf 
and press the
> > "search" button.
> >  
> > Yahoo! Groups Links
> > 
> > 
> > 
> >  
> > 
> > 
> > 
> > 
> > 
> 
> 
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support      
> EnergyPlus-Support@...
>






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