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[EnergyPlus_Support] Re: Zone will not reach setpoint
Dear Richard,
I ran the model with the revised "Central heating design supply air
temperature". Lo and behold, it does a much better job of heating the
zone. Nonetheless, it's still 2C lower than the setpoint, which is
generally considered unacceptable for "real" buildings and won't be a
good representation of actual energy use. Do you have any ideas why
it won't reach the setpoint?
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "JV Dirkes II" <jvd2pe@...>
wrote:
>
> I'll try it!
>
> FYI, ... back earlier in May I posted a problem (Forum message 11377)
> noting that I had non-zero loads in the zones, but the system was
> calculated to have zero flow / load. That file was uploaded and
> called something like "Non-zero loads". Fred Buhl worked on it and
> recommended that I change (guess what?) the "central heating design
> supply temp" from 12.8C to the value it's now at. I sent him an
> e-mail on 5/27 asking about it, but haven't heard back. Fred has the
> "non-zero" file (so do I), but I deleted it from the Forum upload area.
>
> In short, your fix counters an earlier fix. There may be other factors
> which I've inadvertantly altered since the original problem, but I
> want you to be aware of the history....
>
> Also, regarding your last message about using a higher discharge
> setting in the wimter: Good call! That will be one of the savings
> strategies employed for the real building model. This model is a
> "Baseline" for an ASHRAE 90.1 analysis, so I am using the
> ASHRAE-specified HVAC and controls (which do not call for winter reset
> of discharge temp)
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad
> <RRaustad@> wrote:
> >
> > You might also consider using the main air loop heating coil to
pick up
> > more of the load. Why did you choose to heat the air to 12.8C in the
> > main air loop during the winter design day?
> >
> > Richard Raustad wrote:
> > >
> > > Change your "Central heating design supply air temperature (C)" to
> match
> > > what is entering the zone terminal unit heating coil. In this case
> it is
> > > 12.78 C. The zone now maintains 18-20C.
> > >
> > > SYSTEM SIZING,
> > > AirLoop_AH1, !- name of an AIR PRIMARY LOOP object
> > > sensible, !- type of load to size on
> > > Autosize, !- Design (minimum) outside air volumetric
> > > flow rate {m3/s}
> > > 1, !- minimum system air flow ratio
> > > 4.44, !- Preheat design temperature {C}
> > > 0, !- Preheat design humidity ratio
> > > {kg-H2O/kg-air}
> > > 12.78, !- Precool design temperature {C}
> > > 0.0087, !- Precool design humidity ratio
> > > {kg-H2O/kg-air}
> > > 12.78, !- Central cooling design supply air
> > > temperature {C}
> > > 12.78, !- Central heating design supply air
> > > temperature {C} <--------
> > > coincident, !- Sizing Option
> > > no, !- Cooling 100% Outside Air
> > > no, !- Heating 100% Outside Air
> > > 0.0087, !- Central cooling design supply air
> > > humidity ratio {kg-H2O/kg-air}
> > > 0, !- Central heating design supply air
> > > humidity ratio {kg-H2O/kg-air}
> > > design day, !- cooling design air flow method
> > > , !- cooling design air flow rate {m3/s}
> > > design day, !- heating design air flow method
> > > ; !- heating design air flow rate {m3/s}
> > >
> > > JV Dirkes II wrote:
> > > >
> > > > Dear E+ Forum,
> > > >
> > > > I've tried using V2.2.026, since that version addresses a known
> reheat
> > > > problem, but the model still reflects the problems noted in my
last
> > > post.
> > > >
> > > > Can anyone help?
> > > >
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, "JV Dirkes II"
> > > <jvd2pe@>
> > > > wrote:
> > > > >
> > > > > Dear E+ Forum,
> > > > >
> > > > > I am still hoping for some help with this problem. I've added
> report
> > > > > variables, tried different settings, double and triple checked
> all th
> > > > > input, and still cannot get the zone to warm up.
> > > > >
> > > > > Thanks in advance.
> > > > >
> > > > > p.s., The uploaded file is called "ZoneTooCold.zip"
> > > > >
> > > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, "JV Dirkes II"
> <jvd2pe@>
> > > > > wrote:
> > > > > >
> > > > > > Dear E+ Forum,
> > > > > >
> > > > > > My current model includes a variable volume air handler
and VAV
> > > boxes
> > > > > > with reheat coils. The zone which represent 90% of the
building
> > > never
> > > > > > reaches its setpoint on the Winter Design Day.
> > > > > >
> > > > > > Per report variables, the air handler has proper temperature
> heating
> > > > > > hot water (82C) and the discharge temperature is at the
expected
> > > > > > setpoint (12.9C). Air flow is autosized.
> > > > > >
> > > > > > The zone reheat coil is also autosized and has the same
> heating hot
> > > > > > water temperature as the air handler. Per report
variables, the
> > > > > > reheat coil has water flow and is using energy, but only
> heats the
> > > > > > zone to 5C instead of the setpoint (21.1C).
> > > > > >
> > > > > > I've tried manually sizing the reheat coils much larger than
> the
> > > load,
> > > > > > but they continue to use only a small fraction of their
> capacity and
> > > > > > the zone stays too cold. Please let me know what might
> prevent the
> > > > > > reheat coils from warming the zone properly. Thanks!
> > > > > >
> > > > > > p.s., I've uploaded the file in case it will be helpful.
> > > > > >
> > > > >
> > > >
> > > >
> > >
> > > --
> > > 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
> > >
> > >
> >
> > --
> > 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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