Re: [EnergyPlus_Support] Re: Help with override error

"As the zone RH goes to 0, the dehumidification capacity of the cooling coil
should also go to 0 and the zone RH should converge on some low value
but not 0." is not true here in Europe where we always have DOAS.

"Is the outdoor air humidity ratio low?" 32degC 40%RH
"Compare zone humidity ratio to outdoor humidity ratio." Absolute humidity decreased significantly. I had 26degC 0.23% RH in the zone. There was no makeup for the extreamly unbalanced flow from outside and the lack of latent entering load was ignored by eplus as is stated in the warning msg resulting from unbalanced flow.

"Also check ventilation/infiltration rates. Are they high?" No, these were set by me and are what they are set to be, I.e. no AFN was present.

Thanks to your encouragement, the results are extreamly pleasing.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad <RRaustad@...> wrote:
>
> Good detective work. Now you know where to focus your investigations.
>
> When the zone RH is low, this typically means that there is no latent
> load in the space (e.g., people) but then why would RH go to 0. As the
> zone RH goes to 0, the dehumidification capacity of the cooling coil
> should also go to 0 and the zone RH should converge on some low value
> but not 0. Is the outdoor air humidity ratio low? Compare zone humidity
> ratio to outdoor humidity ratio. Also check ventilation/infiltration
> rates. Are they high?
>
> The exhaust fan will only affect the zone return air node air flow rate.
> Exhaust fans can be tricky to implement. You can sum the zone inlet
> nodes and subtract the zone return node flow rate to compare with the
> zone exhaust air flow rate. This difference should be made up from
> outdoor air entering the air loop outside air system.
>
> On 8/4/2011 4:04 AM, Jean marais wrote:
> >
> > OKAY. the humidity and temperatures are about 18 degC and 70%RH at the
> > zone equipment inlet node. The zone air node reports the realistic
> > temperature with the unrealistic humidity. Could it be because of the
> > Fan:ZoneExhaust objects that I have in the zone equipment, is somehow
> > messing up the air balance?
> >
> > My zone equipment looks like this:
> >
> > ZoneHVAC:EquipmentConnections,
> > Underground:Basement, !- Zone Name
> > Underground:BasementEquipment, !- Zone Conditioning Equipment List Name
> > Underground:Basement Supply Inlet, !- List Name: Zone Air Inlet Nodes
> > Underground:Basement WC Exhaust Air Node, !- List Name: Zone Air
> > Exhaust Nodes
> > Underground:Basement Zone Air Node, !- Zone Air Node Name
> > Underground:Basement Return Outlet; !- Zone Return Air Node Name
> >
> > ZoneHVAC:EquipmentList,
> > Underground:BasementEquipment, !- Name
> > ZoneHVAC:AirDistributionUnit, !- Zone Equipment 1 Object Type
> > Underground:Basement ATU, !- Zone Equipment 1 Name
> > 1, !- Zone Equipment 1 Cooling Sequence
> > 1, !- Zone Equipment 1 Heating or No-Load Sequence
> > ZoneHVAC:LowTemperatureRadiant:VariableFlow, !- Zone Equipment 2
> > Object Type
> > Underground:Basement RF, !- Zone Equipment 2 Name
> > 2, !- Zone Equipment 2 Cooling Sequence
> > 2, !- Zone Equipment 2 Heating or No-Load Sequence
> > Fan:ZoneExhaust, !- Zone Equipment 3 Object Type
> > Underground:Basement XFan WC, !- Zone Equipment 3 Name
> > 3, !- Zone Equipment 3 Cooling Sequence
> > 3; !- Zone Equipment 3 Heating or No-Load Sequence
> >
> > !!!!!!!!!!!!!!!Exhaust Fan WC Start
> >
> > Fan:ZoneExhaust,
> > Underground:Basement XFan WC, !- Name WC Exhaust Fan
> > HVACTemplate-Always 1, !- Availability Schedule Name
> > 0.7, !- Fan Efficiency
> > 500, !- Pressure Rise {Pa}
> > 28741, !- Mech ventilation (m3/s) 28741 mÂ³/h
> > Underground:Basement WC Exhaust Air Node, !- Air Inlet Node Name
> > Underground:Basement WC Outside Node, !- Air Outlet Node Name
> > WC Exhaust; !- End-Use Subcategory
> > !!!!!!!!!!!!!!!Exhaust Fan WC End
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, "Jean marais"
> > <jeannieboef@> wrote:
> > >
> > > This morning, I'm going to report more and more system nodes until I
> > find where the RH drops (and I find it very unlikely that this is
> > possible) from 80% (at cooling coil exit node) to 0.2% (in zone) (can
> > one even dry air this much). I suspect a reporting error. Will keep
> > posted what I find.
> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, "Jean marais"
> > <jeannieboef@> wrote:
> > > >
> > > > Hi, back again. Reported the coil air temperatures and humidities
> > entering and leaving, and they seem to be in order. Still don't see
> > where the zone relative humidities drop to fractions.
> > > >
> > > > The current problem submittal has following outputs (if you can
> > think of any other interesting ones, pls let me know:
> > > >
> > > > Output:Variable, *,Plant Loop Cooling Demand,hourly;!HVAC,Average, [W]
> > > > Output:Variable,*, Zone Mean Air Temperature, hourly, On;
> > > > Output:Variable, *, Zone Air Relative Humidity, hourly, On;
> > > >
> > > >
> > > > Output:Variable,DOAS Mixed Air Outlet,System Node
> > Temp,hourly;!HVAC,Average, [C]
> > > > Output:Variable,DOAS Cooling Coil Air Outlet,System Node
> > Temp,hourly;!HVAC,Average, [C]
> > > > Output:Variable,DOAS Mixed Air Outlet,System Node Humidity
> > Ratio,hourly;!HVAC,Average, [C]
> > > > Output:Variable,DOAS Cooling Coil Air Outlet,System Node Humidity
> > Ratio,hourly;!HVAC,Average, [C]
> > > > Output:Variable,DOAS Mixed Air Outlet,System Node Relative
> > Humidity,hourly;!HVAC,Average, [C]
> > > > Output:Variable,DOAS Cooling Coil Air Outlet,System Node Relative
> > Humidity,hourly;!HVAC,Average, [C]
> > > >
> > > > ! OutputControl:Table:Style,
> > > > ! comma; !- Column Separator
> > > > ! Output:Table:SummaryReports,
> > > > ! AllSummary; !- Report 1 Name
> > > >
> > > > !Output:Surfaces:Drawing, DXF, Triangulate3DFace;
> > > >
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, "Jean marais"
> > <jeannieboef@> wrote:
> > > > >
> > > > > Understood. I'll take a sharper look and get back to the thread
> > later.
> > > > >
> > > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad
> > <RRaustad@> wrote:
> > > > > >
> > > > > > Does your input file include report variables for inlet air T
> > and W, air
> > > > > > flow rate, coil cooling rate, etc. to use for debugging? Have you
> > > > > > checked the eio file for any indications of size of this coil?
> > Being a
> > > > > > developer, I typically do not run files posted on the yahoo
> > groups web
> > > > > > site since this is a peer-to-peer site.
> > > > > >
> > > > > > On 8/3/2011 9:50 AM, Jean marais wrote:
> > > > > > >
> > > > > > > Hi Richard,I now specified both and the error went away, but
> > now I get
> > > > > > > garbage comming out with humidities of zero instead of close
> > to 100%.
> > > > > > > I'm putting the 20110721.epmidf.zip in the problem files area.
> > > > > > >
> > > > > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad
> > > > > > > <RRaustad@> wrote:
> > > > > > > >
> > > > > > > > This probably relates to your problem. You tell the
> > program to chose
> > > > > > > the
> > > > > > > > inlet air humrat, but then specify the outlet air humrat.
> > > > > > > >
> > > > > > > > autosize, !- Design Inlet Air Humidity Ratio {kg-H2O/kg-air}
> > > > > > > > 0.0010, !- Design Outlet Air Humidity Ratio Entering is
> > 0.01178 ,0.0050
> > > > > > > > does not work
> > > > > > > >
> > > > > > > > I would run the program for the sizing period and report
> > the outdoor T
> > > > > > > > and W to see how these values change. That warning looks
> > like one that
> > > > > > > > should provide more information. Alternately you could
> > specify both or
> > > > > > > > autosize both.
> > > > > > > >
> > > > > > > > On 8/3/2011 8:52 AM, Jean marais wrote:
> > > > > > > > >
> > > > > > > > > Hi Richard,
> > > > > > > > >
> > > > > > > > > I've set the coil and it was working until I upped the
> > entering
> > > > > > > > > humidity. I now get:
> > > > > > > > > ** Warning ** SizeWaterCoil: Coil="DOAS COOLING COIL",
> > Cooling Coil
> > > > > > > > > has leaving humidity ratio > entering humidity ratio.
> > > > > > > > > ** ~~~ ** ..will be sized for 50% of entering humidity
> > ratio.
> > > > > > > > >
> > > > > > > > > EVENTHOUGH entering air from outside has humidity of
> > 0.01178 and the
> > > > > > > > > coil is set to 0.001.
> > > > > > > > >
> > > > > > > > > SizingPeriod:DesignDay, Summer Design Day in BBI
> > Terminal, !- Design
> > > > > > > > > Day Name
> > > > > > > > > 32.0, !- Max Dry-Bulb {C}
> > > > > > > > > 10.3, !- Daily Temp Range {C}
> > > > > > > > > 0.01178,!21.74, !- Wet-Bulb at Max {C} gH2O/gDryAir
> > > > > > > > > 100761.7, !- Barometric Pressure {N/M**2}
> > > > > > > > > 0, !- Wind Speed {m/s}
> > > > > > > > > 0, !- Wind Direction {Degrees N=0, S=180}
> > > > > > > > > 0.98, !- Clearness {0.0 to 1.1}
> > > > > > > > > 0, !- Rain {0-no,1-yes}
> > > > > > > > > 0, !- Snow on ground {0-no,1-yes}
> > > > > > > > > 15, !- Day of Month
> > > > > > > > > 7, !- Month
> > > > > > > > > SummerDesignDay, !- Day Type -- used for schedules
> > > > > > > > > 1, !- Daylight Savings Time Indicator
> > > > > > > > > HumidityRatio,!WetBulb, !- Type of humidity temperature
> > Indicator
> > > > > > > > > , !- Relative Humidity Day Schedule(not used)
> > > > > > > > > , !- Dry-Bulb Temperature Range Modifier Type (not used)
> > > > > > > > > ; !- Dry-Bulb Temperature Range Modifier Schedule (not used)
> > > > > > > > >
> > > > > > > > > Coil:Cooling:Water,
> > > > > > > > > DOAS Cooling Coil, !- Name
> > > > > > > > > 2, !- Availability Schedule Name
> > > > > > > > > autosize, !- Design Water Flow Rate of Coil {m3/s}
> > > > > > > > > autosize, !- Design Air Volume Flow Rate {m3/s}
> > > > > > > > > 6,!autosize, !- Design Inlet Water Temperature {C}
> > > > > > > > > 32,!autosize, !- Design Inlet Air Temperature {C}
> > > > > > > > > 18,!autosize, !- Design Outlet Air Temperature {C}
> > > > > > > > > autosize, !- Design Inlet Air Humidity Ratio {kg-H2O/kg-air}
> > > > > > > > > !autosize, !- Design Outlet Air Humidity Ratio
> > {kg-H2O/kg-air}
> > > > > > > > > 0.0010, !- Design Outlet Air Humidity Ratio Entering is
> > 0.01178
> > > > > > > > > ,0.0050 does not work
> > > > > > > > > DOAS Cooling Coil ChW Inlet, !- Coil Water Inlet Node
> > > > > > > > > DOAS Cooling Coil ChW Outlet, !- Coil Water Outlet Node
> > > > > > > > > DOAS Mixed Air Outlet, !- Air Inlet Node Name
> > > > > > > > > DOAS Cooling Coil Air Outlet, !- Air Outlet Node Name
> > > > > > > > > DetailedAnalysis, !- Type of Analysis
> > > > > > > > > CrossFlow; !- Heat Exchanger Configuration
> > > > > > > > >
> > > > > > > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > > > > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > > > > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, "Jean marais"
> > > > > > > > > <jeannieboef@> wrote:
> > > > > > > > > >
> > > > > > > > > > I have the following error:
> > > > > > > > > >
> > > > > > > > > > ************* Beginning System Sizing Calculations
> > > > > > > > > > ************* Beginning Plant Sizing Calculations
> > > > > > > > > > ** Warning ** In calculating the design coil UA for
> > > > > > > > > Coil:Cooling:Water DOAS COOLING COIL
> > > > > > > > > > ** ~~~ ** the apparatus dew-point is below the coil
> > design inlet
> > > > > > > > > water temperature;
> > > > > > > > > > ** ~~~ ** the coil bypass factor is unrealistically large;
> > > > > > > > > > ** ~~~ ** the coil outlet design conditions will be
> > changed to
> > > > > > > > > correct the problem.
> > > > > > > > > > ** ~~~ ** The initial design conditions are: Tair,in =
> > 24.4500
> > > > > > > > > > ** ~~~ ** Wair,in = 9.478796E-003
> > > > > > > > > > ** ~~~ ** Twater,in = 6.0000
> > > > > > > > > > ** ~~~ ** Tair,out = 18.0000
> > > > > > > > > > ** ~~~ ** Wair,out = 8.000000E-003
> > > > > > > > > > ** ~~~ ** The revised design conditions are: Tair,out
> > = 14.5987
> > > > > > > > > > ** ~~~ ** Wair,out = 9.371939E-003
> > > > > > > > > >
> > > > > > > > > > All my coil inputs possible are autosized. Zone and
> > System humidity
> > > > > > > > > designs are 0.008 (default). My outlet Tair design is 18
> > deg (as seen
> > > > > > > > > in the error msg.)
> > > > > > > > > >
> > > > > > > > > > 1) What is going on here exactly?
> > > > > > > > > > 2) How can I enter other parameters so that the error
> > does not
> > > > > > > occur
> > > > > > > > > and no reheat is nessesary.
> > > > > > > > > >
> > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > > > --
> > > > > > > > Richard A. Raustad
> > > > > > > > Senior Research Engineer
> > > > > > > > Florida Solar Energy Center
> > > > > > > > University of Central Florida
> > > > > > > > 1679 Clearlake Road
> > > > > > > > Cocoa, FL 32922-5703
> > > > > > > > Phone: (321) 638-1454
> > > > > > > > Fax: (321) 638-1439 or 1010
> > > > > > > > Visit our web site at: http://www.fsec.ucf.edu
> > > > > > > >
> > > > > > > > UCF - From Promise to Prominence: Celebrating 40 Years
> > > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > > --
> > > > > > Richard A. Raustad
> > > > > > Senior Research Engineer
> > > > > > Florida Solar Energy Center
> > > > > > University of Central Florida
> > > > > > 1679 Clearlake Road
> > > > > > Cocoa, FL 32922-5703
> > > > > > Phone: (321) 638-1454
> > > > > > Fax: (321) 638-1439 or 1010
> > > > > > Visit our web site at: http://www.fsec.ucf.edu
> > > > > >
> > > > > > UCF - From Promise to Prominence: Celebrating 40 Years
> > > > > >
> > > > >
> > > >
> > >
> >
> >
>
> --
> Richard A. Raustad
> Senior Research Engineer
> Florida Solar Energy Center
> University of Central Florida
> 1679 Clearlake Road
> Cocoa, FL 32922-5703
> Phone: (321) 638-1454
> Fax: (321) 638-1439 or 1010
> Visit our web site at: http://www.fsec.ucf.edu
>
> UCF - From Promise to Prominence: Celebrating 40 Years
>