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Re: [EnergyPlus_Support] Re: Minimum O.A.

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Re: Minimum O.A.
From: "Michael J. Witte" <mjwitte@xxxxxxxx>
Date: Mon, 22 Oct 2007 16:38:53 -0500
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I have been running this input file (and some variations) and noticed that the 
zones are not meeting setpoint.  This may be impacting the sensitivity of 
heating load to outside air quantity.  I would suggest reporting space 
temepratures and "Time Heating Setpoint Not Met[" to be sure the simulation is 
performain as expected.

Mike


On 18 Oct 2007 at 13:58, Richard Raustad wrote:

> Judith, you must mean you don't see a significant change in heating 
> energy. If I add up all the hot water coil rates (W) for the main 
> heating coil and the 6 zone coils, I get 283 kW at 9am on Tuesday, Jan 
> 1. This drops to 277 kW when I change the minOA schedule from 1 to 0.5 
> from 7am to 4pm. Reducing the OA by half results in a 6kW reduction in 
> heating load at 9am. This is a very small change compared to the very 
> large heating load in the entire building (2%).
> 
> 
> Judith Peters wrote:
> >
> > Dear Richard,
> >
> > Thank you for your speedy reply. I agree with all the points that you 
> > made in your letter.
> >
> > Here's my problem. When using the Min OA Sched (for an annual 
> > simulation or for a weekday), I adjust my Min OA Sched from 1.0 to 
> > 0.50 between the hours of 7a.m. and 4p.m., but see no change in 
> > heating energy.
> >
> > When I have tried this with similar files, I see a downward adjustment 
> > of between 20 and 30 percent of heating energy, since the building is 
> > located in Northern Minnesota.
> >
> > Any other suggestions? Thank you for your time. I really appreciate it.
> >
> > Judy
> >
> > Richard Raustad <RRaustad@xxxxxxxxxxxx 
> > <mailto:RRaustad%40FSEC.UCF.EDU>> wrote:
> > Judith, I can not duplicate your conditions exactly. Your inputs must be
> > different than those in the file you uploaded. For instance, I get the
> > following design volumetric flow rates using the Duluth, MN weather file:
> >
> > Component Sizing, AIR PRIMARY LOOP, VAV SYS 1, Primary air design
> > volumetric flow rate [m3/s], 11.249
> > Component Sizing, CONTROLLER:OUTSIDE AIR, OA CONTROLLER 1, maximum
> > outside air flow rate [m3/s], 11.249
> > Component Sizing, CONTROLLER:OUTSIDE AIR, OA CONTROLLER 1, minimum
> > outside air flow rate [m3/s], 0.69856
> >
> > But I can tell you that the minimum outside air schedule you used is
> > limiting the amount of outside air provided by the outside air
> > controller. You used a multiplier of 0.02 from midnight to 7 am and
> > again from 4pm to midnight. The minimum outside air schedule is used as
> > a multiplier for the minimum outside air flow rate specified in the
> > outside air controller. So instead of getting 0.69856 m3/s, you will get
> > 0.01397 m3/s during these times. If you change the minimum outside air
> > schedule values to 1.0 for all hours (everywhere in your schedule) you
> > will get the minimum outside air you expect. Also note that the schedule
> > values apply to specific day types. The first part of the schedule
> > applies to week days and the summer design day. The second part of the
> > schedule applies to all other days, including the winter design day
> > since it was not specified in the first part of the schedule (in the
> > "for" input). If you leave the schedule as shown below you will see
> > 0.01397 m3/s during the morning and evening hours and 0.69856 m3/s
> > during the day on the summer design day. But you will see only 0.01397
> > m3/s for all hours on the winter design day. For an annual run, the
> > first part of the schedule applies to week days and the second part of
> > the schedule applies to weekends and holidays.
> >
> > Does this answer your question?
> >
> > CONTROLLER:OUTSIDE AIR,
> > OA Controller 1, !- Name
> > ECONOMIZER, !- EconomizerChoice
> > NO RETURN AIR TEMP LIMIT,!- ReturnAirTempLimit
> > NO RETURN AIR ENTHALPY LIMIT, !- ReturnAirEnthalpyLimit
> > NO LOCKOUT, !- Lockout
> > FIXED MINIMUM, !- MinimumLimit
> > Mixed Air Node 1, !- Control_Node
> > Outside Air Inlet Node 1,!- Actuated_Node
> > autosize, !- minimum outside air flow rate {m3/s}
> > autosize, !- maximum outside air flow rate {m3/s}
> > 19., !- temperature limit {C}
> > 4., !- temperature lower limit {C}
> > 0.0, !- enthalpy limit {J/kg}
> > Relief Air Outlet Node 1,!- Relief_Air_Outlet_Node
> > VAV Sys 1 Inlet Node, !- Return_Air_Node
> > Min OA Sched; !- Minimum Outside Air Schedule Name
> >
> > SCHEDULE:COMPACT,
> > Min OA Sched, !- Name
> > Fraction, !- ScheduleType
> > Through: 12/31, !- Complex Field #1
> > For: WeekDays SummerDesignDay CustomDay1 CustomDay2, !- Complex
> > Field #2
> > Until: 7:00, !- Complex Field #3
> > 0.02, !- Complex Field #4
> > Until: 8:00, !- Complex Field #5
> > 1.00, !- Complex Field #6
> > Until: 9:00, !- Complex Field #7
> > 1.00, !- Complex Field #8
> > Until: 10:00, !- Complex Field #9
> > 1.00, !- Complex Field #10
> > Until: 12:00, !- Complex Field #11
> > 1.00, !- Complex Field #12
> > Until: 13:00, !- Complex Field #13
> > 1.00, !- Complex Field #14
> > Until: 16:00, !- Complex Field #15
> > 1.00, !- Complex Field #16
> > Until: 17:00, !- Complex Field #17
> > 0.02, !- Complex Field #18
> > Until: 24:00, !- Complex Field #19
> > 0.02, !- Complex Field #20
> > For: AllOtherDays, !- Complex Field #21
> > Until: 24:00, !- Complex Field #22
> > 0.02; !- Complex Field #23
> >
> > Judith Peters wrote:
> > >
> > > Hi Richard,
> > >
> > > Thank you for your reply. I am using a variable fan with a VAV system.
> > > The file is an adaptation of the 5ZoneVAV Example File. My overall
> > > maximum air flow is 10.709 m^3/s. For outside air, the eio file states
> > > a minimum of 1.8125 m^3/s to a maximum of 10.709 m^3/s.
> > >
> > > I have uploaded the file. Thank you very much for your help.
> > >
> > > Judy Peters
> > >
> > > Richard Raustad <RRaustad@xxxxxxxxxxxx <mailto:RRaustad%40FSEC.UCF.EDU>
> > > <mailto:RRaustad%40FSEC.UCF.EDU>> wrote: What type of HVAC system are you
> > > using? If a cycling fan system is used and the average system flow rate is
> > > less than the minimum outside air flow rate, you will get 100% outside air
> > > and the flow rate may drop below the minimum you expect. The outside air
> > > flow rate can not be greater than the mixed air flow rate. Compare the
> > > outdoor air flow rate to the mixed air (or HVAC system) flow rate and see if
> > > they are equal during these times. If you can not find a reason for this
> > > problem, please upload your file to the Files/Problem_Submittals folder so
> > > an EnergyPlus team member can take a closer look.
> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > <mailto:EnergyPlus_Support%40yahoogroups.com>, Judith Peters
> > > <jdth_peters@...> wrote:
> > > >
> > > > Dear EnergyPlus Group,
> > > >
> > > > When I adjust the minimum outdoor air level, I do not see a
> > > corresponding change in my heating and cooling rates/consumption.
> > > >
> > > > I followed your suggestion and set the controller to "fixed"
> > > instead of "proportional", but I am still having the problem.
> > > >
> > > > Any suggestions?
> > > >
> > > > Thank you for your help!
> > > >
> > > > Judy Peters
> > > >
> > > >
> > > > ---------------------------------
> > > > Don't let your dream ride pass you by. Make it a reality with
> > > Yahoo! Autos.
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > >
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> > >
> >
> > -- 
> > 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 <http://www.fsec.ucf.edu>
> >
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> >
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> >
> >  
> 
> -- 
> 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
> 
> 
> 
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> 
> 
> 
> 


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





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References:
- Re: [EnergyPlus_Support] Re: Minimum O.A.
  - From: Judith Peters
- Re: [EnergyPlus_Support] Re: Minimum O.A.
  - From: Richard Raustad

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