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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: Thu, 13 Apr 2006 17:50:59 -0500
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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
> > 
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> > 
> > 
> > 
> 
> 
> 
> 
> [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





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Follow-Ups:
- Re: [EnergyPlus_Support] Errors in some zones and not others
  - From: Sam Roose

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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