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Re: [EnergyPlus_Support] Errors in some zones and not others

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Errors in some zones and not others
From: "Michael J. Witte" <mjwitte@xxxxxxxx>
Date: Wed, 19 Apr 2006 12:19:09 -0500
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The chilled water design setpoint is 7C, but the CW-Loop-Temp-Schedule is set 
to 12.  Changing this schedule to 7C to match the sizing criteria improves the 
situation greatly.

Next, the economizer is running wild on the Zone 1 air loop.  On the summer 
design day, the system is running at 100% outside air.  Turning on RETURN AIR 
ENTHALPY LIMIT fixes this.  Or if you do not expect to use an enthalpy control, 
the max outdoor dry bulb limit should be set to something below the zone design 
dewpoint condition (if I remember correctly).

Finally, the ZONE SIZING cooling supply temperature is 14C which means that the 
supply air flow rate to that zone will be sized to meet the zone sensible 
design cooling load.  The SYSTEM SIZING cooling supply temperature is 13C.  
This helps to size the cooling coil a bit larger, but it is not enough.  There 
are two issues going on here, first, in order to provide humidity control, the 
cooling coil must be able to deliver air below this.  There is also a known bug 
with COIL:SIMPLE:COOLING in which it does not autosize adequately.  So you will 
need to experiment with a lower SYSTEM SIZING cooling supply temp until this is 
fixed.  Using 10C produced reasonable results.

Mike


On 19 Apr 2006 at 18:53, Sam Roose wrote:

> Thanks for that explanation. I have uploaded my file again  the
> temperatures are not converging even with the changes belo and a simpler
> system. The file is ³20_SYSTEM_CHANGES.idf. I have also tried putting
> temperature limits on the economiser with little change to temperature
> convergence and some unexpected results. I am not convinced my autosizing
> inputs and the reheat manager are agreeing with each other. The example
> files I have found give conflicting information on typical temperatures for
> autosizing. Is this where I am going wrong? My main goal at this stage is to
> have this system meeting its setpoints with autosized inputs. Thanks in
> advance
> 
> Sam
> 
> On 4/14/06 10:50 AM, "Michael J. Witte" <mjwitte@xxxxxxxx> wrote:
> 
> > Sorry, my instructions were not clear regarding the control and setpoint
> > nodes. 
> > Going back to the original file:
> > 
> > Original - NODE LIST,
> >     Zone 1 Supply Air Temp Nodes,  !- Node List Name
> >     Zone 1 Cooling Coil Outlet Node;  !- Node_ID_1
> > 
> > (Note that this node list was doing nothing in the original file - it was
> > never 
> > referenced.)
> > 
> > Modified - NODE LIST,
> >     Zone 1 Supply Air Temp Nodes,  !- Node List Name
> >     Zone 1 Cooling Coil Outlet Node,  !- Node_ID_1
> >     Zone 1 Air Loop Outlet Node; !- Node_ID_2
> > 
> > Next, we have the set point manager
> > 
> > Original - SET POINT MANAGER:SINGLE ZONE REHEAT,
> >     Zone 1 Air Temp Manager, !- Name
> > <snip>
> >     Zone 1 Cooling Coil Outlet Node;  !- Name of the set point Node . . .
> > 
> > Modified - SET POINT MANAGER:SINGLE ZONE REHEAT,
> >     Zone 1 Air Temp Manager, !- Name
> > <snip>
> >     Zone 1 Supply Air Temp Nodes;  !- Name of the set point Node . . .
> > 
> > This now applies the same set point to two nodes, the node leaving the
> cooling
> > coil *and* the node leaving the heating coil.  The reason you need this is
> > because the TEMPandHUMRAT control will lower the setpoint at the node
> leaving
> > the cooling coil when additional dehumidification is required.  The
> setpoint
> > on 
> > the heating coil leaving node remains untouched by the humidity controls,
> and
> > so the heating coil knows how much to reheat the overcooled air.
> > 
> > Then for the controllers, the cooling coil controller should use "Zone 1
> > Cooling Coil Outlet Node" as the control node, and the heating coil should
> use
> > "Zone 1 Air Loop Outlet Node" as the control node.  Likewise, of course,
> for
> > the other similar systems.
> > 
> > Regarding the system configuration, if you intend to have just one zone
> per
> > system, the easiest approach would be to delete the heating coil in the
> main
> > air branch (and its controller) and just let the reheat coil in the SINGLE
> > DUCT:CONST VOLUME:REHEAT terminal unit handle all heating and reheating. 
> Then
> > all of the above becomes moot, and the original controls should work fine
> for
> > the cooling coil (assuming the TEMPandHUMRAT fix is in place).  Or keep
> the
> > central heating coil and change the SINGLE DUCT:CONST VOLUME:REHEAT
> terminal
> > units to DIRECT AIR (which does not require and AIR DISTRIBUTION UNIT
> object).
> > 
> > Mike
> > 
> > 
> > On 13 Apr 2006 at 17:21, Sam Roose wrote:
> > 
> >> > Thanks Mike  should have seen the humidity rate issue. I still have
> the
> >> > same errors as before, although I have sent an updated attempt based on
> the
> >> > 5ZoneBoilerOutsideAirReset example file (in terms of the nodes used at
> >> > least). This is called ³20_Node_Changes²
> >> > 
> >> > Referring to reply 2b, my attempts to run a simulation with the
> separate
> >> > single zone reheat node list did not work. I gather the approach is to
> >> leave
> >> > the existing node list as they are and make a new one for the ³single
> zone
> >> > reheat² control? I am not sure I understand the instructions or the need
> >>
> for
> >> > two node Ids in that case.
> >> > 
> >> > You make a good point about the heating coil within the air loop and
> the
> >> > reheat coil being excessive. Is there an example file with just a
> cooling
> >> > coil and a heating coil in an air loop? I can¹t seem to find one. Thanks
> >>
> for
> >> > your help thus far.
> >> > 
> >> > Sam
> >> > 
> >> > 
> >> > 
> >> > On 4/13/06 3:14 AM, "Michael J. Witte" <mjwitte@xxxxxxxx> wrote:
> >> > 
> >>> > > 
> >>> > > 
> >>> > > On 7 Apr 2006 at 18:46, Sam Roose wrote:
> >>> > > 
> >>>>> > >> > I have uploaded a file named 18_manager_changes that when run
> in
> >> > Version
> >>>>> > >> > 1.2.3.031 gives me three errors.
> >>>>> > >> > 
> >>>>> > >> > 1) Calculated design heating load for zone = OUTPATIENT 2 is
> zero.
> >> > Check
> >>>>> > >> > zone sizing and zone thermostat inputs.
> >>>>> > >> >
> >>>>> > >> >     The specification for OUTPATIENT 2 is no different to the
> other
> >> > zones
> >>>>> > >> > with respect to zone sizing and zone thermostat inputs.
> Hopefully,
> this
> >>>>> > >> > isn't due to the use of multiple air loops.
> >>>>> > >> > 
> >>> > > 
> >>> > > 
> >>> > > 1.  This means the zone has no need for heating on the heating
> design
> >>> day.
> >>> > > The 
> >>> > > zone sizing calculation only relies on the building envelope,
> >>> thermostat,
> >> > and
> >>> > > zone sizing objects.  It knows nothing of the HVAC system at this
> point
> in
> >> > the
> >>> > > calculation, including any fresh air the HVAC system may be
> introducing.
> >> > So,
> >>> > > this is a loads balance issue for the winter design day.  If I'm
> reading
> >> > the
> >>> > > drawing and inputs correctly, this zone is a large, part interior,
> part
> >>> > > exterior zone with a small amount of glass.  So this result may be
> >> > correct,
> >>> > > but 
> >>> > > you should double check the internal gains.
> >>> > > 
> >>> > > The zone loads are used only to determine the air volume flow rate
> for
> >> > that
> >>> > > zone.  The system coils are then sized to deliver the specified
> supply
> air
> >>> > > temperatures are that flow rate, so the coil load will include the
> >>> outside
> >> > air
> >>> > > loads.
> >>> > > 
> >>>>> > >> > 2) Maximum iterations exceeded for three different air loops:
> Zone
> 7,
> >> > Zone
> >> > 8
> >>>>> > >> > and Zone 23, all quite large zones and mostly internal to the
> >>>>> building.
> >> > Why
> >>>>> > >> > is this?
> >>> > > 
> >>> > > 2. Max iteration errors indicate the system could not converge on a
> >> > solution.
> >>> > > This can be due to inconsistent controls causing battling, or a
> variety
> of
> >>> > > other reasons.  I see two problems in the controller:simple inputs:
> >>> > > 
> >>> > > 2a.  There are HUMIDISTAT and SET POINT MANAGER:SINGLE ZONE MAX HUM
> >> > objects,
> >>> > > so 
> >>> > > I presume you want humidity control.  All of the cooling coi
> controllers
> >> > are
> >>> > > currently set for Control variable = TEMP.  For humidity control
> these
> >>> must
> >> > be
> >>> > > set to TEMPandHUMRAT.  They are currently controlling just for the
> dry
> >> > bulb
> >>> > > setopint.  (I've posted a suggestion to warn of this condition.)
> >>> > > 
> >>> > > 2b.  The supply duct heating coil controllers (I'm presuming these
> are
> >> > reheat
> >>> > > for the humidity control) are using "Zone 4 Cooling Coil Outlet Node"
> as
> >> > the
> >>> > > control node, but that is the air inlet to the coil.  This most
> likely
> why
> >>> > > there are max iteration errors and poor control.  To fix this,
> change
> the
> >>> > > control node to be the heating coil air outlet node (e.g. Zone 1 Air
> >>>
> Loop
> >>> > > Outlet Node).  This node also needs a setpoint.  In the SET POINT
> >>> > > MANAGER:SINGLE ZONE REHEAT, the "Name of the set point Node or Node
> >>>
> List"
> >>> > > needs 
> >>> > > to be a node list which lists both the cooling coil outlet node and
> the
> >> > air
> >>> > > loop outlet node (which is the heating coil outlet).
> >>> > > 
> >>> > > 2c.  I am a bit puzzled at this system configuration.  The way it is
> >> > described
> >>> > > now, it appears that the cooling coil and heating coil in the main
> air
> >> > loop
> >>> > > branch will do all of the control and the zone-level reheat coil is
> >>> > > unneccessary.
> >>> > > 
> >>> > > Mike
> >>> > > 
> >>> > > 
> >>>>> > >> > 
> >>>>> > >> > 3) Temperatures out of comfort range, despite everything being
> >> > autosized.
> >>>>> > >> > Mostly it is a result of overheating due to this building
> having
> high
> >>>>> > >> > internal gains. However, the number of hours temperatures are
> out
> of
> >> > range
> >>>>> > >> > is high in some cases. Can this be reduced?
> >>>>> > >> > 
> >>>>> > >> > Thanks in advance,
> >>>>> > >> > 
> >>>>> > >> > Sam Roose
> >>>>> > >> > 
> >>>>> > >> > 
> >>>>> > >> > 
> >>>>> > >> > 
> >>>>> > >> > 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.idf
> and
> >> > press
> >>>> > >> the
> >>>>> > >> > "search" button.
> >>>>> > >> >  
> >>>>> > >> > Yahoo! Groups Links
> >>>>> > >> > 
> >>>>> > >> > 
> >>>>> > >> > 
> >>>>> > >> >  
> >>>>> > >> > 
> >>>>> > >> > 
> >>>>> > >> > 
> >>>>> > >> > 
> >>>>> > >> > 
> >>> > > 
> >>> > > 
> >>> > > ========================================================
> >>> > > Michael J. Witte, GARD Analytics, Inc.
> >>> > > EnergyPlus Testing and Support
> >>> > > EnergyPlus-Support@xxxxxxxx
> >>> > > 
> >>> > > 
> >>> > > 
> >>> > > 
> >>> > > 
> >>> > > 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.idf and
> >>>
> press
> >> > the
> >>> > > "search" button.
> >>> > > 
> >>> > > 
> >>> > > 
> >>> > > 
> >>> > > YAHOO! GROUPS LINKS
> >>> > > 
> >>> > > *  Visit your group "EnergyPlus_Support
> >>> > > <http://groups.yahoo.com/group/EnergyPlus_Support> " on the web.
> >>> > > *  
> >>> > > *  To unsubscribe from this group, send an email to:
> >>> > > *  EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx
> >>> > >
> >> >
> <mailto:EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx?subject=Unsubscribe>
> >>> > > *  
> >>> > > *  Your use of Yahoo! Groups is subject to the Yahoo! Terms of
> Service
> >>> > > <http://docs.yahoo.com/info/terms/> .
> >>> > > 
> >>> > > 
> >>> > > 
> >> > 
> >> > 
> >> > 
> >> > 
> >> > [Non-text portions of this message have been removed]
> >> > 
> >> > 
> >> > 
> >> > 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.idf and
> press
> >> the
> >> > "search" button.
> >> >  
> >> > Yahoo! Groups Links
> >> > 
> >> > 
> >> > 
> >> >  
> >> > 
> >> > 
> >> > 
> >> > 
> > 
> > 
> > ========================================================
> > Michael J. Witte, GARD Analytics, Inc.
> > EnergyPlus Testing and Support
> > EnergyPlus-Support@xxxxxxxx
> > 
> > 
> > 
> > 
> > 
> > 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.idf and press
> the
> > "search" button.
> > 
> > 
> > 
> > 
> > YAHOO! GROUPS LINKS
> > 
> > *  Visit your group "EnergyPlus_Support
> > <http://groups.yahoo.com/group/EnergyPlus_Support> " on the web.
> > *  
> > *  To unsubscribe from this group, send an email to:
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> >
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> > *  Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service
> > <http://docs.yahoo.com/info/terms/> .
> > 
> > 
> > 
> 
> 
> 
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> 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.idf and press the
> "search" button.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> 


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





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.idf and press the "search" button.
 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
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References:
- Re: [EnergyPlus_Support] Errors in some zones and not others
  - From: Michael J. Witte
- Re: [EnergyPlus_Support] Errors in some zones and not others
  - From: Sam Roose
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