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Re: [EnergyPlus_Support] Re: Minimum O.A.
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>
>
> UCF - From Promise to Prominence: Celebrating 40 Years
>
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> [Non-text portions of this message have been removed]
>
>
--
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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