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[EnergyPlus_Support] Fwd: Re: Cooling set-point not fully achieved

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Fwd: Re: Cooling set-point not fully achieved
From: "anarui.oliveira" <anarui.oliveira@xxxxxxxxx>
Date: Thu, 07 Feb 2008 18:21:54 -0000
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Differences go up to 1ºC. Does it fit the behaviour of the problem 
you describe?

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad 
<RRaustad@...> wrote:
>
> I have looked at this control issue before. I don't think it's the 
> mixing objects or other zone loads. And your offset from the set 
point 
> should be pretty small. Not to worry, the overall annual energy use 
> should be pretty close. Beside, if you run this building using a 
> different building simulation tool, your likely to get a different 
> answer. And I believe the difference in these answers will be 
greater 
> than the difference in annual energy use due to the set point 
offset. If 
> it happens all the time, adjust your set point so the "average" 
zone 
> temperature is near your target temperature.
> 
> anarui.oliveira wrote:
> >
> > Could the mixing objects or anything like that contribute to this
> > problem? Or some definitions such as humidity ratios or the 
like?...
> > Getting worried here... the aim was exactly to predict the energy
> > consumption of a building throughout a year (for official, legal
> > purposes)...
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, "anarui.oliveira"
> > <anarui.oliveira@> wrote:
> >
> > Is this problem equally likely to happen if I use a Purchased Air
> > approach?
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad
> > <RRaustad@> wrote:
> > >
> > > You could try increasing the time step in hour. I have no other
> > > suggestions. This is a known issue and we are working to 
correct it.
> > >
> > > anarui.oliveira wrote:
> > > >
> > > > That field is already set to 1, and time step in hours is set 
to
> > 4.
> > > >
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad
> > > > <RRaustad@> wrote:
> > > > >
> > > > > What you describe is not a capacity issue, it is related to 
the
> > > > > prediction of loads. If you add the report variable
> > for "Zone/Sys
> > > > > Sensible Load Predicted" and set the report variable 
frequency
> > to
> > > > > detailed, you will see why this is happening. Try reducing 
the
> > > > Minimum
> > > > > System Time Step in the System Convergence Limits object. 
You
> > > > probably
> > > > > will not eliminate the problem, but it should get better.
> > > > >
> > > > >
> > > > > anarui.oliveira wrote:
> > > > > >
> > > > > > What if, in a similar (heating) case, water flow doesn't
> > reach the
> > > > > > maximum when the problem occurs, and increasing the air 
flow
> > > > causes
> > > > > > further departure from temperature setpoint?...(Less than
> > about
> > > > 1.5
> > > > > > times the auto-sized air flow also leads to poorer 
setpoint
> > > > > > tracking); reported air flow is always equal to the 
constant
> > > > volume
> > > > > > fan flow, and ouside air flow rate is (and must be) user
> > > > specified.
> > > > > >
> > > > > > Regards,
> > > > > > Ana.
> > > > > >
> > > > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard 
Raustad
> > > > > > <RRaustad@> wrote:
> > > > > > >
> > > > > > > Then try again to manually size the coil in the problem
> > zone to
> > > > > > twice
> > > > > > > the size reported in the eio file. Also increase the air
> > flow
> > > > rate
> > > > > > for
> > > > > > > that fan coil unit and fan to twice the autosized 
value. If
> > > > htis is
> > > > > > > happening in more than 1 zone, then just pick 1 for now 
to
> > test
> > > > > > this out.
> > > > > > >
> > > > > > > Then tell me what happens to the maximum zone 
temperature.
> > Did
> > > > the
> > > > > > > maximum zone temperature go down? Also tell me if the 
water
> > flow
> > > > > > rate is
> > > > > > > at a maximum when the zone temperature exceeds the set
> > point.
> > > > You
> > > > > > can
> > > > > > > report "System Node VolFlowRate" for the coil water 
inlet
> > node
> > > > and
> > > > > > fan
> > > > > > > coil air inlet node to easily match volumetric flow rate
> > with
> > > > your
> > > > > > inputs.
> > > > > > >
> > > > > > > This just sounds like a sizing issue and should be 
easily
> > > > resolved.
> > > > > > >
> > > > > > > anarui.oliveira wrote:
> > > > > > > >
> > > > > > > > Apparently, yes, but I set it to autosize (and I 
think I
> > > > already
> > > > > > did
> > > > > > > > a trial with a larger, user-defined, water flow 
rate)...
> > > > > > > >
> > > > > > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > > > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > > > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard
> > Raustad
> > > > > > > > <RRaustad@> wrote:
> > > > > > > > >
> > > > > > > > > I have not looked at your input file, can you tell 
me
> > if the
> > > > > > water
> > > > > > > > mass
> > > > > > > > > flow rate through the fan coil is at a maximum when 
the
> > > > cooling
> > > > > > set
> > > > > > > > > point is not met?
> > > > > > > > >
> > > > > > > > > anarui.oliveira wrote:
> > > > > > > > > >
> > > > > > > > > > Please forgive me for insisting, but I DO have 
some
> > > > urgency on
> > > > > > > > this
> > > > > > > > > > one...
> > > > > > > > > > Again, thanks for any help,
> > > > > > > > > > Ana.
> > > > > > > > > >
> > > > > > > > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > > > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > > > > > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > > > > > > > <mailto:EnergyPlus_Support%
> > > > > > 40yahoogroups.com>, "anarui.oliveira"
> > > > > > > > > > <anarui.oliveira@> wrote:
> > > > > > > > > > >
> > > > > > > > > > > Hi again.
> > > > > > > > > > >
> > > > > > > > > > > I'm uploading a new file 
(Zone36598_cFancoil_exp),
> > > > hoping
> > > > > > that
> > > > > > > > > > someone
> > > > > > > > > > > can help me figure out why the cooling setpoints
> > are not
> > > > > > being
> > > > > > > > > > achieved
> > > > > > > > > > > for all times when the controls are active 
(namely
> > in
> > > > Zone
> > > > > > > > 36598).
> > > > > > > > > > The
> > > > > > > > > > > model consists of Fancoil units created with 
Compact
> > > > HVAC,
> > > > > > and
> > > > > > > > then
> > > > > > > > > > > edited in the expanded file.
> > > > > > > > > > > I tried several user-defined and sizing 
options, but
> > > > > > couldn't
> > > > > > > > solve
> > > > > > > > > > the
> > > > > > > > > > > temperature peaks above 25ºC.
> > > > > > > > > > >
> > > > > > > > > > > Thanks in advance,
> > > > > > > > > > > Ana Rui.
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > > > --
> > > > > > > > > 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>
> > > > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>>
> > > > > > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu> 
> > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>>>
> > > > > > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu> 
> > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>>
> > > > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu> 
> > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>>>>
> > > > > > > > >
> > > > > > > > > UCF - From Promise to Prominence: Celebrating 40 
Years
> > > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > > > --
> > > > > > > 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>
> > > > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>>
> > > > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu> 
> > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>>>
> > > > > > >
> > > > > > > UCF - From Promise to Prominence: Celebrating 40 Years
> > > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > > --
> > > > > 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>
> > <http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>>
> > > > >
> > > > > UCF - From Promise to Prominence: Celebrating 40 Years
> > > > >
> > > >
> > > >
> > >
> > > --
> > > 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
> > >
> >
> > --- End forwarded message ---
> >
> >  
> 
> -- 
> 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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