# [EnergyPlus_Support] Re: zone load calculation?

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Hi,
Thanks.
I don't understand specifying temperature controls.Does it mean
that i should specify zone control:thermostic?I'am puzzled.
Take 5ZoneEngChill.idf for a example:single heating setpoint is 12.8
(1am-7am and 6pm-12pm) and 21.1(7am-6pm);single cooling setpoint is 40
(1am-7am and 6pm-12pm) and 23.9(7am-6pm).I don't understand these
temperature values.Does these values describe the temp demand of user?
How can i get the real temperature of the thermostic?I guess zone/sys
air temp describe this values(Is it right?).Meanwhile,i found the
lower temp of the single cooling setpoint(23.9) should be bigger than
the upper temp of the single heating setpoint(21.1),if not ,there is
warning.
problem 2:The supply air temperature is 16(while heating) and 12.8
(while cooling).I don't know how can these two temperature can
maintain the zone temperature in 21(heating) and 23.9(cooling)?For
example ,the zone temp is 14 and the supply air temp is 16(vav
outlet),how can the zone temp rise to 21?i'am puzzled.At least,the
supply air temp should >21?
problem 3:Last time,i ask the problem of the zone/sys sensible
heating/cooling rate.Mike tells me,when zone temp(temp of thermostic)
>16,report cooling;<16 heating.It occurs while the vav system is
off.But when vav system is on,what values should i take to compare
with?
problem 4:If i specify the temperature control and the HVAC.I want
to get zone load.Do the zone/sys sensible heating/cooling can
represent it?
problem 5:following is my understand for the three temp,right???
zone thermostat setpoint:describe temp demand of the user.
zone temperatures:the temp of the thermostic
system supply air temperature:vav system outlet temp,is fixed at 16
(heating) and 12.8(cooling).

help.Thanks.
Bless to you!
pch

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte"
<mjwitte@g...> wrote:
> In order to determine heating and cooling loads in EnergyPlus, you
need to
> specify temperature controls and some type of HVAC system.  The
simplest system
> is "purchased air" which is an infinite supply of hot and cold
air.  This can
> be used to calculate loads without specifying a full HVAC system.
There is a
> sample file called "PurchAir.idf" in the EnergyPlus\ExampleFiles
folder which
> will show you the objects required.
>
> However, it is critical that users understand the limitations of
the PURCHASED
> AIR model.  The description of the model and its outputs beings on
p. 520 of
> the Input Output Reference (pdf p. 548, version 1.2.0).
>
> Mike
>
> On 2 Dec 2004, at 12:17, hbn_pch wrote:
>
> >
> >
> > Dear,
> >   I meet a new problem.For a long time,i calculate zone load with
the
> > sum of the Zone-Total Internal Radiant Heat Gain,Zone-Total
Internal
> > Convective Heat Gain,Zone-Total Internal Visible Heat Gain,Zone-
Total
> > Internal Latent Gain and Zone-Total Internal Radiant Heat
> > Gain.Today,i found these values are just the internal load,such
as
> > people,lights and equipments(Is it right?).
> >   Then a problem come in,how can i calculate the zone load?In
other
> > words,what report variables should i add in the report variable
> > object to calculate the zone load???
> >   Another problem,in the .eio<Zone Sizing Information>,the
cooling
> > and heating load is the load in the design day(Is it right?).Are
> > these two load values calculated in the worst condition?Are they
> > biggest?
> >   I'am a newbie in this field,appreciated to your kind help.Thanks
> >
> >   pch
> >
> >
> >
> >
> >
> >
> >
> > 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.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
>
>
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support
> EnergyPlus-Support@g...

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