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Re: [EnergyPlus_Support] Re: about the minimum system air flow ratio
If SET POINT MANAGER:WARMEST had little impact on the results, this implies to
me that this system is serving a mix of zones in which the cooling vs. heating
load pattern is not the same. Perhaps a core zone with a high cooling load
requires a lower supply air temperature which is too cold for perimeter zones
during mild weather? It may be necessary to have two different air handlers,
one for core and one for perimeter zones, or maybe increase the supply air
volume to the zones with the highest cooling demands. I am just guessing here.
First, turn on more report variables to understand what is happening in this
system. Report the vav damper positions (Damper Position), supply air
temperatures (System Node Temp), supply air setpoints (System Node Setpoint
Temp), the heating and cooling coil loads, the mixed air temperature, and the
outside air inlet node flow rate. Something is causing the system to fight
with itself.
On 14 Nov 2004, at 12:13, beyangj wrote:
>
>
> Dear,
> Thank you very much for your reply! I used SET POINT MANAGER:WARMEST
> to reset the supply air temperature as mentioned by Mike and did the
> simulation again, but it didn't seem to work. The heating was also
> needed all the year round, and the amount needed was similar to that
> before.The smaller the minimum system air flow ratio and the zone
> minimum air flow fraction were set, the smaller heating would be
> used in the summer and winter. Compared the simulation results with
> that simulated using DOE-2.1E, the cooling energy was similar, but
> the heating energy was greatly different, and there was no heating
> in the summer in the DOE-2.1E simulation results, and all the
> parameters were the same in the EnergyPlus model and the Doe-2.1E
> model. The heating energy simulated using DOE-2.1E was much larger
> than that simulated using EnergyPlus in winter when the minimum
> system air flow ratio and the zone minimum air flow fraction were
> set as smaller values so as to have a smaller heating energy in the
> EnergyPlus model. I want to know how can I get the reasonable
> results? Could you give me some more advice? Thanks again!
>
> Best,
>
> Stewart
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte"
> <mjwitte@g...> wrote:
> > If humidity control is not an issue, you can use SET POINT
> MANAGER:WARMEST to
> > reset the supply air temperature. This will reduce the amount of
> summer reheat
> > required but will also increase fan power. Or you can schedule
> reheat coils
> > off for the summer and let the spaces overcool.
> >
> > Mike
> >
> > On 11 Nov 2004, at 10:54, Edward Lyon wrote:
> >
> > >
> > > You may not have a simulation mistake. A variable air volume
> system
> > > will use heat during summer cooling to avoid over cooling a
> space. For
> > > instance, if your system discharges 50F air, but the cooling
> load only
> > > requires 60F air at the minimum flow volume, heat will be needed
> to
> > > maintain set point temperature. Typically you will need a cold
> supply
> > > air temperature to lower the dew point of the ventilation air for
> > > humidity control. Maintaining humidity control requires heating
> to
> > > avoid over cooling the space.
> > >
> > > Ned Lyon
> > >
> > > Senior Project Manager
> > > Simpson Gumpertz & Heger Inc.
> > >
> > > 41 Seyon Street
> > > Building #1, Suite 500
> > > Waltham, MA 02453
> > >
> > > Phone: 781-907-9000
> > > Fax: 781-907-9009
> > >
> > >
> > > >>> beyangj@h... 11/11/2004 10:03:09 AM >>>
> > >
> > > Dear,
> > > In my simulation, the minimum system air flow ratio and the zone
> > > minimum air flow fraction were varied several times, and that
> > > affected the result of cooling energy slightly, but that
> affected
> > > the result of heating energy obviously. I am wondering why
> there is
> > > some heating in the summer days, and the heating just occurs in
> the
> > > period the system is turned on. When the ratio and the fraction
> > > mentioned before are set smaller, the heating in the summer
> would
> > > also become smaller. As a matter of fact, there is no heating in
> the
> > > summer days, but there is always some heating in the summer days
> > > even the minimum system air flow ratio is set as 0.01. How can I
> get
> > > rid of this mistake? In addition, I want to know how much these
> > > ratio values affect the results. Thanks in advance!
> > >
> > > Best,
> > >
> > > Stewart
> > >
> > >
> > >
> > >
> > >
> > >
> > > The primary EnergyPlus web site is found at:
> > > http://www.energyplus.gov
> > >
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> > > http://groups.yahoo.com/group/EnergyPlus_Support/
> > >
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> >
> > ========================================================
> > Michael J. Witte, GARD Analytics, Inc.
> > EnergyPlus Testing and Support
> > EnergyPlus-Support@g...
>
>
>
>
>
>
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