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



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
> 
> 
> 
> 
> 
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