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Re: [EnergyPlus_Support] Re: zone load calculation?

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Re: zone load calculation?
From: "Michael J. Witte" <mjwitte@xxxxxxxx>
Date: Mon, 6 Dec 2004 16:32:38 -0600
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1.  These are thermostat setpoints.  During the daytime, when people are 
present, heat to 21.1C or cool to 23.9C.  All other hours, heat to 12.8C or 
cool to 40C (which essentially means the cooling is off).

2.  This is a reheat system.  The supply air setpoint is the temperature 
supplied to the VAV terminal units.  The reheat coils heat the air further to 
maintain the desired temperature in the zones.  

3.  "Zone/Sys Air Temp" is the actual air temperature in the zone.  "Schedule 
Value" for the heating and cooling setpoint schedules are the thermostat 
setpoints.  The system may or may not be able to meet the thermostat setpoint, 
or the zone air temperature may be floating in the deadband between heating and 
cooling.

4.  If the thermostat setpoint is met, then "zone/sys sensible heating/cooling" 
is the sensible zone load.

5.  See answers above.

Mike


On 6 Dec 2004, at 11:58, hbn_pch wrote:

> 
> 
> 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).
> 
>   I'm ablush for asking so many questions.But appreciated your kind 
> 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.
> > > 
> > > 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
> 
> 
> 
> 
> 
> 
> 
> 
> 






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References:
- Re: [EnergyPlus_Support] zone load calculation?
  - From: Michael J. Witte
- [EnergyPlus_Support] Re: zone load calculation?
  - From: hbn_pch

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