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Re: [EnergyPlus_Support] Re: Zone components of a 2-pipe system?



Sorry I forgot about the thermostat.

To have EnergyPlus size your system, I would suggest the following steps:

1.  If I understand your system correctly, the central air system with direct 
air terminal units is providing ventilation air, so first set the ZONE SIZING 
and SYSTEM SIZING objects to size this system.  

2.  Make a new version of the input file, and use the component sizing results 
in the eio output from step 1 to put hard sizes in the components of the 
central system.

3.  Change the zone sizing and system sizing objects to have appropriate values 
for the fan coil systems.  Run this for summer and winter design days and 
report the peak heating/cooling delivered by the fan coils.  At this point the 
challenge is to easily downsize the fan coils without entering hard values for 
all of the fan coil components.

4.  One approach might be to make a new version of the step 3 input file and 
turn off the central system by changing the availability manager schedule.  
Again, report the peak heating/cooling delivered by the fan coils.  The ratio 
of peak loads between step 3 and step 4 could be used to determine sizing 
factors for the fan coils zones?

Mike


On 11 Feb 2008 at 22:13, anarui.oliveira wrote:

> In case anyone else is interested in similar modelling, Compact HVAC 
> also duplicates zone thermostatic controls, so one (per zone) must 
> be deleted and there's some minor node connection adjustments to be 
> done, but it was fairly simple and it worked beatifully.
> I had values to define the HVAC components, but if I wanted to auto-
> size, given the issue you mentioned, what would you suggest 
> (priority 1 to Direct Air and priority 2 to FanCoil)?
> 
> Thanks,
> Ana.
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
> <mjwitte@...> wrote:
> >
> > > Another question, to add to the previous:
> > > - The Compact HVAC approach doesn't let us define both a 
> Zone:VAV and 
> > > a FanCoil? (I get errors about duplicate Zone sizing objects...)
> > 
> > That is correct.  Compact HVAC currently supports only one system 
> per zone.  
> > But the workaround is fairly straightforward, unless you have a 
> large number of 
> > zones.
> > 
> > 1.  Using the idf file you have already created, take the expidf 
> output file 
> > and save it to a new name as .idf
> > 
> > 2.  For each zone served by the vav and fan coil, delete one of 
> the ZONE SIZING 
> > objects.  Note that EnergyPlus sizing does not recognize that 
> there are two 
> > systems serving a zone - it will try to size both system to meet 
> the full load, 
> > but that's another issue.  Let's get this file running first.
> > 
> > 3.  For each zone served by the vav and fan coil, there are also 
> duplicate 
> > CONTROLLED ZONE EQUIP CONFIGURATION and ZONE EQUIPMENT LIST 
> objects.  You must 
> > merge these objects into one of each for each zone.  The final 
> CONTROLLED ZONE 
> > EQUIP CONFIGURATION object will have 2 zone inlet nodes, a zone 
> air node, one 
> > exhaust node, and one return node.  In order to specify 2 inlet 
> nodes, you will 
> > need to create a NODE LIST object which lists the two inlets and 
> then use the 
> > NODE LIST name in the CONTROLLED ZONE EQUIP CONFIGURATION object.  
> > 
> > With these changes, the file should run.
> > 
> > Mike
> > 
> > On 4 Feb 2008 at 16:15, anarui.oliveira wrote:
> > 
> > > Another question, to add to the previous:
> > > - The Compact HVAC approach doesn't let us define both a 
> Zone:VAV and 
> > > a FanCoil? (I get errors about duplicate Zone sizing objects...)
> > > 
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "anarui.oliveira" 
> > > <anarui.oliveira@> wrote:
> > > >
> > > > Thanks a lot.
> > > > 
> > > > The Central AHU has a heat recovery component, which receives 
> the 
> > > > return airflow from more than 1 zone, so I think I should keep 
> the 
> > > > two levels of the heating/cooling process?...as opposed to 
> letting 
> > > > the fan-coils addressing the full thermal load?...
> > > > In this case, it appears it wouldn't actually be easier to 
> treat 
> > > the 
> > > > heat recovery by "manual" post-processing?...Or are there any 
> known 
> > > > downsides to this two-level approach?
> > > > 
> > > > At the moment, is there any approach in E+ that would 
> accurately 
> > > > mimic the system I described? I mean, could I actually (with 
> nore 
> > > or 
> > > > less "manual work"), set up both a heating and a cooling coil 
> to 
> > > act 
> > > > on the supply air, at zone level, setting both coils operation 
> to 
> > > > depend on the zone thermostat (at the moment, I don't really 
> need 
> > > > many details on this, I would just like to know the 
> possibilities)?
> > > > 
> > > > Again, thanks a lot,
> > > > Ana Rui.
> > > > 
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
> > > > <mjwitte@> wrote:
> > > > >
> > > > > If I am understanding the system correctly, the simplest 
> approach 
> > > > would be to 
> > > > > use the 4-pipe fan coil with mutually exclusive schedules 
> for the 
> > > > heating and 
> > > > > cooling coils.  However, do not set the inlet conditions to 
> be 
> > > from 
> > > > the central 
> > > > > ahu, simply let the fancoil unit carry the entire load.  
> > > > > 
> > > > > It is not clear to me whether it matters that the 
> heaitng/cooling 
> > > > be modeled in 
> > > > > two parts.  If it does matter, then I would still use the 4-
> pipe 
> > > > fan coil, but 
> > > > > with no outside air.  And then describe a constant volume 
> air 
> > > loop 
> > > > which 
> > > > > delivers the partially conditioned outside air using a 
> direct air 
> > > > terminal unit 
> > > > > in each zone.  If the direct air unit is listed with heating 
> and 
> > > > cooling 
> > > > > priority 1,  then the fan coil will pick up any remaining 
> load.
> > > > > 
> > > > > Mike
> > > > > 
> > > > > 
> > > > > On 26 Jan 2008 at 17:03, anarui.oliveira wrote:
> > > > > 
> > > > > > Hello, all.
> > > > > > 
> > > > > > I'm having a hard time to figure out the best options to 
> model 
> > > a 
> > > > > > specific 2-pipe HVAC configuration...
> > > > > > 
> > > > > > Any ideas about which could be the simplest way to 
> approximate 
> > > > the 
> > > > > > zone level model of a 2-pipe (constant volume) system with:
> > > > > > - an AHU that delivers 100% OA at inermediate 
> heated/cooled 
> > > > > > temperatures (18/27 ºC) to the zone level,
> > > > > > - where a battery with either hot or chilled water coil 
> > > (mutually 
> > > > > > exclusive at any given moment, and necessarily in the same 
> > > > operation 
> > > > > > regime - heating or cooling - serving the central AHU) 
> meets 
> > > the 
> > > > > > additional load (when needed),
> > > > > > - raising/decreasing the air temperature of the supply air 
> loop 
> > > > to 
> > > > > > design Temperatures of 35ºC(heating) or 16ºC (cooling), to 
> meet 
> > > > Room 
> > > > > > Air setpoint conditions according to a 20-25ºC thermostat?
> > > > > > 
> > > > > > The "Single Duct:Const Volume: Reheat" and "Single 
> Duct:Const 
> > > > Volume:4 
> > > > > > pipe" don't quite seem to reproduce this behaviour?...
> > > > > > 
> > > > > > No recirculating or induced air from the room actually 
> happens 
> > > in 
> > > > the 
> > > > > > real situation (the zone level re-conditioning is 
> performed 
> > > > directly 
> > > > > > and uniquely in the air supplied by the AHU, and then 
> delivered 
> > > > to the 
> > > > > > room, where the mixed model should take care of the 
> rest)...
> > > > > > ...but perhaps, in terms of global thermal loads and 
> energetic 
> > > > > > analysis, it wouldn't be too far fetched to use
> > > > > > - "Single Duct:Const Volume:4 pipe"
> > > > > > or
> > > > > > - "direct air" and "fan coil: 4 pipe"
> > > > > > with mutually exclusive availability schedules for the 
> coils 
> > > and 
> > > > > > design air inlet temperatures equal to the setpoints of 
> AHU 
> > > > supply 
> > > > > > air?...
> > > > > > ... the main differences between these options being?...
> > > > > > 
> > > > > > Better options?...
> > > > > > 
> > > > > > Thanks in advance,
> > > > > > Ana Rui.
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > 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.
> > > > > > 
> > > > > > EnergyPlus Documentation is searchable.  Open 
> EPlusMainMenu.pdf 
> > > > under the
> > > > > > Documentation link and press the "search" button.
> > > > > > 
> > > > > > Yahoo! Groups Links
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > 
> > > > > 
> > > > > ========================================================
> > > > > Michael J. Witte, GARD Analytics, Inc.
> > > > > EnergyPlus Testing and Support      
> > > > > EnergyPlus-Support@
> > > > >
> > > >
> > > 
> > > 
> > > 
> > > 
> > > 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.
> > > 
> > > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf 
> under the
> > > Documentation link and press the "search" button.
> > > 
> > > Yahoo! Groups Links
> > > 
> > > 
> > > 
> > > 
> > > 
> > 
> > 
> > ========================================================
> > Michael J. Witte, GARD Analytics, Inc.
> > EnergyPlus Testing and Support      
> > EnergyPlus-Support@...
> >
> 
> 
> 
> 
> 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.
> 
> EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the
> Documentation link and press the "search" button.
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 


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



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