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RE: [EnergyPlus_Support] Re: Setpoint not met during night cycle
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]
------------------------------------
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