[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[EnergyPlus_Support] Re: Setpoint not met during night cycle
Dear Brent,
I see YOUR point! I was using a 6C on/off tolerance, which is pretty
large, but in this case seemed warranted.
After thinking about your response, it seems to me that we're asking
E+ to make assumptions about how the system "should" run. In my case,
it assumed that my system "should" be able to achieve the setpoint
within the cycle period. I'd rather that it ran until it met the
setpoint, partly because that's the way I think it "should" run,
partly because I don't want to do the trial and error work of
experimenting with an optimal cycle period, and partly because I can't
imagine a real system that would operate in the manner E+ now operates
the system.
That said, this is not a big deal in the overall scope of the program.
I appreciate your consideration!
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Griffith, Brent"
<brent_griffith@...> wrote:
>
> I see your point, but the night cycle manager is usually used with a
> thermostat schedule that is setback/setup at night. Unless you use an
> unusually large value for Thermostat On/Off Tolerance, when the system
> kicks on it isn't very far away from set point and capacity should be
> plenty to quickly reach the relatively easy set points during setback.
> So in practice, it should reach setpoint when "on", but could drift
> pretty far if cycled "off" for too long. But if the system can't safely
> float for any length of time, maybe the system shouldn't be getting
> turned off at night in the first place.
>
>
>
> ________________________________
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of JV Dirkes II
> Sent: Monday, April 14, 2008 12:12 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Re: Setpoint not met during night cycle
>
>
>
> Dear Fred,
>
> Thanks for the reply.
>
> Suggestion for future development:
> Allow E+ to run for as many consecutive "Cycling run time" cycles as
> needed to achieve the setpoint.
>
> If, as is now the case, it shuts off after every cycle and waits for
> the next cycle to attempt to reach the setpoint -- it may NEVER reach
> the setpoint. This, of course, does not act like any typical control
> sequence. It also forces the modeler to experiment with the "Cycling
> run time" to make the unoccupied period reasonably close to setpoint,
> and even then, it's an approximation that is more accurate / less
> accurate depending on the outdoor conditions.
>
> Thanks for all the work you do!
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> , Fred Buhl <wfbuhl@>
> wrote:
> >
> > It is supposed to run work that way, though as you point out that
> > it may not make the most sense.. Thanks for solving your own problrm!
> >
> > Fred
> >
> > JV Dirkes II wrote:
> > > Dear E+ Forum,
> > >
> > > After experimenting some more, it appears that the SYSTEM
> AVAILABILITY
> > > MANAGER:NIGHT CYCLE "Cycling run time" was preventing the zone from
> > > reaching the setpoint. When I set it for 900s (15 min), it would
> turn
> > > the system OFF at the end of that period, even though the setpoint
> was
> > > not met. In other words, it came ON for 900s, turned OFF for 900S,
> > > then ON for 900s , etc.
> > >
> > > When I set the "Cycling run time" for 3600s, it operates on a longer
> > > cycle, which allows the zone to warm properly. Of course the fan
> runs
> > > a lot more, too!
> > >
> > > I guess I've solved my own problem for now, but still have a
> question:
> > >
> > > 1) Is the SYSTEM AVAILABILITY MANAGER:NIGHT CYCLE supposed to work
> > > this way? It seems to me that a control system should operate in
> > > NIGHT CYCLE as long as needed to achieve the setpoint, and then shut
> > > off. My first understanding of the "Cycling run time" was as a
> > > MINIMUM run time. That's apparently incorrect, but it seems to be
> > > more appropriate....
> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> , "JV Dirkes II" <jvd2pe@>
> > > wrote:
> > >
> > >> Dear EPlus Forum,
> > >>
> > >> Please help me determine why my model maintains proper setpoints
> > >> during Winter Design Days in the "night" period, but fails to do
> so on
> > >> other winter days.
> > >>
> > >> During the night, the setpoints are as expected, the system cycles
> on
> > >> and off as expected (I'm using a SYSTEM AVAILABILITY MANAGER:NIGHT
> > >> CYCLE), but the zone temp is much lower than the setpoint
> (including
> > >> the thermostat on/off tolerance).
> > >>
> > >> I'll upload the file....
> > >>
> > >>
> > >
> > >
> > >
> > > ------------------------------------
> > >
> > > The primary EnergyPlus web site is found at:
> > > http://www.energyplus.gov <http://www.energyplus.gov>
> > >
> > > The group web site is:
> > > http://groups.yahoo.com/group/EnergyPlus_Support/
> <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
> > >
> > >
> > >
> > >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
>
>
>
> [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/