[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [EnergyPlus_Support] Re: Minimum O.A.
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> 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>> 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>, 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]
> >
>
> ---------------------------------
> Take the Internet to Go: Yahoo!Go puts the Internet in your pocket:
> mail, news, photos & more.
>
> [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
---------------------------------
Catch up on fall's hot new shows on Yahoo! TV. Watch previews, get listings, and more!
[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.pdf under the Documentation link and press the "search" button.
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/EnergyPlus_Support/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/EnergyPlus_Support/join
(Yahoo! ID required)
<*> To change settings via email:
mailto:EnergyPlus_Support-digest@xxxxxxxxxxxxxxx
mailto:EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx
<*> To unsubscribe from this group, send an email to:
EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/