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Re: [EnergyPlus_Support] Re: zoning problems



The heating setpoint is 20C, the cooling setpoint is 26C, and the thermostat 
schedules include setback and seasonal availability of heating or cooling.  The 
building has many windows on the exterior walls.  

In the 3-zone case in January, the solar gains through the windows serve to 
offset heating loads in a large portion of the building.  In the 9-zone case in 
January, the solar gains heat just the perimeter zones and the interior zones 
must be heated mechanically, less heat flow through the dividing walls.

Because cooling is not available in the winter, the zones overheat, reaching 
temperatures in the 25-30C range.  In the 3-zone case there is less 
overheating, because the solar gains are distributed over a larger zone.  In 
the 9-zone case there is more overheating.  On cold days, such as the winter 
design day, the difference in heating load is only 6%.  On mild days, the 
difference is very large, because the solar gains are wasted in the exterior 
zones causing them to be warmer than needed.

This does not cause a problem in the cooling comparison, becuase the solar 
gains become a cooling load in both cases.

For a valid comparison of loads, the zones in both runs must be at the same 
temperatures.  To do this, use the single heating cooling setpoint control 
option so that the conditioned zones are controlled to the same temperature 
with heating and cooling available at all times.  Then compare the net load 
(heating minus cooling) between the two cases.  I expect they will be very 
similar.

Mike



On 15 Aug 2005, at 22:16, Michael J. Witte wrote:

> It is difficult to guess why this is happening without seeing the input files. 
> Please upload both files to the yahoo files area or send zipped to energyplus-
> support@xxxxxxxx
> 
> Mike
> 
> 
> On 11 Aug 2005, at 4:34, energypluser wrote:
> 
> > Hi Mike
> > 
> > My setpoint schedule for each zone is the same. And I compared the 
> > heating load and cooling load for a heating month and a cooling 
> > month. For the heating month, there is no cooling load at all. So I 
> > am confused about the net load comparasion. The most weird thing is 
> > that the cooling loads of two cases are similiar, but the heating 
> > load of 9 zone with no wall is 80% more than that of 3 zone. 
> > The heating load is the total load of the building.
> > Can you explain it to me ?
> > Thank you in advance. 
> > 
> > charlie
> > 
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
> > <mjwitte@g...> wrote:
> > > (Responding to this post rather than yesterday's posts.)  
> > > 
> > > There are many reasons this could happen - differences in radiant 
> > exchange, 
> > > differences in thermal mass effects, differences in distribution 
> > of solar 
> > > gains, excess heat from the interior zone heating the perimeter 
> > zones.  
> > > Remember, if the simulation model describes no surfaces or mixing 
> > between the 
> > > interior and perimeter zones (in the 9-zone case) then there is no 
> > heat 
> > > transfer between them.  In the 3-zone case, there is convective 
> > and radiative 
> > > exchange between the perimeter walls and the interior surfaces and 
> > internal 
> > > loads.  A more valid comparison is the "net load" of the two cases 
> > over an 
> > > entire day or year (assuming the spaces are heated and cooled to 
> > the same 
> > > temperature at all times), where "net load" = Heating load minus 
> > Cooling Load.  
> > > This should account for offsetting loads in the interior and 
> > perimeter spaces.
> > > 
> > > Mike
> > > 
> > > 
> > > On 9 Aug 2005, at 14:30, energypluser wrote:
> > > 
> > > > I have divided my building into 9 zones without using interior 
> > walls
> > > > as you sugguested. For the real building, there are only 3 
> > zones.The
> > > > following figure shows the plan view of the floor.The center 
> > zone is
> > > > uncontrolled.The north and south zone are served by purchased 
> > air.
> > > > -------------------
> > > > |                 |
> > > > |                 |
> > > > |                 |
> > > > |-----------------|
> > > > |                 |
> > > > |-----------------|
> > > > |                 |
> > > > |                 |
> > > > |                 |               
> > > > -------------------
> > > > For the specificaiton of perimeter zone and interior zone, the
> > > > following picture shows the zoning.
> > > > 
> > > > -------------------
> > > > |    perimeter    |
> > > > |-----------------|
> > > > | |   interior  | |
> > > > | |             | |
> > > > |-----------------|
> > > > | |
> > > > |-----------------|
> > > > | |             | |
> > > > | |  interior   | |
> > > > |-----------------|
> > > > |    perimeter    |
> > > > -------------------
> > > > 
> > > > The perimeter and interior zone have the same schedule and same
> > > > internal gains. Since there are no wall among these zones. I 
> > suppose
> > > > that the load results should be close for the two situations. But
> > > > the heating load of the second case is larger than that of the 
> > first
> > > > case. The max differenc is up to 120%.
> > > > Could you please tell me the reason for the difference?
> > > > Thank you in advance
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 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.
> > > > 
> > > > Yahoo! Groups Links
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > 
> > > 
> > > 
> > > ========================================================
> > > Michael J. Witte, GARD Analytics, Inc.
> > > EnergyPlus Testing and Support      
> > > EnergyPlus-Support@g...
> > 
> > 
> > 
> > 
> > 
> > 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.
> > 
> > Yahoo! Groups Links
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> 
> 
> 
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support      
> EnergyPlus-Support@xxxxxxxx
> 
> 
> 
> 
> 
> 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.
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 
> 
> 
> 



========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx




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