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Re: [EnergyPlus_Support] Re: About the heating load



Based on a review of the input files for the initial request below, it appears 
that the zero coil size is expected.  

For sizing a heating coil, the minimum system flow rate is used.  For the VAV 
system, this results in 100% outside air.  For the CAV system, this results in 
approximately 22% outside air.  With a return air temperature of 19.8C and a 
design outside air temperature of 4 C, the heating design mixed air temperature 
is 16.3C, which is greater than the SYSTEM SIZING heating supply temperature of 
16C.  That is why the main heaing coil sizes to zero which indicatest that this 
system type does not need a central heating coil for the specified design 
conditions.

Raising the heating supply air temperature gives the heating coil a non-zero 
size.

On 10 May 2005, at 9:28, civilnug wrote:

> I was getting the exact same warning in a simulation I am working on 
> at the momemt. I had values in SYSTEM SIZING for 
> Central cooling design supply air temperature {C} and 
> Central heating design supply air temperature {C}
> different values in ZONE SIZING for 
> Zone cooling design supply air temperature {C} and
> Zone heating design supply air temperature {C}.
> 
> I have a single zone single duct VAV with no reheat but when 
> I made the heating supply temperature the same for the system and 
> the zone and likewise for the cooling supply temperatures it got rid 
> of the warning.
> 
> John McCarthy.
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "beyangj" <beyangj@h...> 
> wrote:
> > Dear Mike,
> > Thank you very much for your reply. The system in my model was a 
> air-
> > cooled CAV system for commercial building. Yes, there were reheat 
> > coils in this system, and the zone setpoints were maintained by 
> > specifying the dayschedule. In order to compare the energy 
> > consumption of different systems, the IDF file for this CAV system 
> > was modified from the IDF file for VAV system, and there were no 
> > such warnings as mentioned before when running the IDF file for 
> the 
> > VAV system. The inputs in the SYSTEM SIZING object for the CAV 
> > system are set as follow:
> > 
> > SYSTEM SIZING,
> >     CAV Sys 1,               !- name of an AIR PRIMARY LOOP object
> >     sensible,                !- type of load to size on
> >     autosize,                !- Design (minimum) outside air 
> > volumetric flow rate {m3/s}
> >     1,                       !- minimum system air flow ratio
> >     15.0,                    !- Preheat design set temperature {C}
> >     13,                      !- Central cooling design supply air 
> > temperature {C}
> >     16,                      !- Central heating design supply air 
> > temperature {C}
> >     noncoincident,           !- Sizing Option
> >     no,                      !- Cooling 100% Outside Air
> >     no,                      !- Heating 100% Outside Air
> >     .008,                    !- Central cooling design supply air 
> > humidity ratio {kg-H2O/kg-air}
> >     0.008,                   !- Central heating design supply air 
> > humidity ratio {kg-H2O/kg-air}
> >     design day,              !- cooling design air flow method
> >     0,                       !- cooling design air flow rate {m3/s}
> >     design day,              !- heating design air flow method
> >     0.0;                     !- heating design air flow rate {m3/s}
> > 
> > I still don¡¯t know why this happened, could you give me more 
> > advices?
> > 
> > Best,
> > 
> > Stewart 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
> > <mjwitte@g...> wrote:
> > > What type of system is this for?  Are there other heating coils 
> > such as reheat 
> > > coils?  Are the zone setpoints being maintained?  Check the 
> inputs 
> > in the 
> > > SYSTEM SIZING object.  Coil sizing is determined by the 
> specified 
> > supply air 
> > > temperatures, the system flow rate, and the mixed air 
> temperature 
> > at the design 
> > > load condition.
> > > 
> > > Mike
> > > 
> > > 
> > > On 29 Apr 2005, at 8:55, beyangj wrote:
> > > 
> > > > Dear,
> > > > There was a warning in the ERR file as follow:
> > > > ** Warning ** The design coil load is zero for 
> > > > COIL:Water:SimpleHeating MAIN HEATING COIL 1
> > > >    **   ~~~   ** The autosize value for max water flow rate is 
> > zero
> > > >    **   ~~~   ** To change this, input a value for UA, change 
> > the 
> > > > heating design day, or lower
> > > >    **   ~~~   **   the system heating design supply air 
> > temperature
> > > > 
> > > > I don't know why this happened. I changed the heating design 
> > day, 
> > > > but it didn't work,and it gave the same warning message. And 
> the 
> > > > Heating:Electricity [J](RunPeriod) in the Meter file wasn't 
> > zero, it 
> > > > was 3.90248E+12J, and the heating load is correct in this 
> case? 
> > > > Thanks in advance!
> > > > 
> > > > Best,
> > > > 
> > > > Stewart
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 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




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