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[EnergyPlus_Support] Re: Heating/Setpoint Controller



Thanks Karen, yes that may work. I really don't have only a single zone, so I will try to choose the zone with the highest loads as the control zone (they have VAV boxes).
I guess that the only way to automatically choose the appropiate zone for control would be using E+ EMS.

Karen, I will try to see if it works. Thanks again.

Germán.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Karen Walkerman <kwalkerman@...> wrote:
>
> Ah, I understand your issue better now.  I have not modeled your exact
> setup, but I still think I can help.  Take a look at the example file:
> SmOffPSZ-MultiModeDX.idf
> 
> This file uses both a SetpointManager:SingleZone:Heating and a
> SetpointManager:SingleZone:Cooling object to establish temperatures on the
> loop in order to condition a single zone.
> 
> --
> Karen
> 
> On Sat, Apr 14, 2012 at 6:02 AM, ecoeficientees <ecoeficiente@...>wrote:
> 
> > **
> >
> >
> > Thanks Karen for your answer, I agree with your description. I will try to
> > explain the problem better (I think the key is in the dual setpoint).
> > When you have two coils, you can have a setpoint manager at the outlet (as
> > you say) that works for both or a setpoint manager at the outlet of each
> > coil that controls each of them independently.
> >
> > If you need to mantain a constant setpoint at the outlet, there is no
> > problem. You specify, for example, 14ºC and both coils work together to get
> > that temperature. The problem is that, when you have, in the same day, a
> > cooling demand (which you can offset with the 14ºC supply air) followed by
> > a heating demand (eg. at night), you still have the 14ºC setpoint which is
> > useless.
> >
> > For that situation, I tried to specify one setpoint for each coil (eg.
> > 14ºC for cooling and 30ºC for heating) hoping that depending on the final
> > demand in the zone(s) one of the coils would shut off.
> > The result, however, is that both coils are on, each of them trying to
> > reach its setpoint and you end up with both coils opposing each other.
> >
> > It seems to be impossible to use the AHU for both heating and cooling
> > unless you specify availability schedules for the coils. The problem is
> > that you cannot predict when you will be needing each load.
> > Am I right?
> >
> > Regards,
> >
> > Germán.
> >
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Karen Walkerman <kwalkerman@>
> > wrote:
> > >
> > > German,
> > >
> > > I think you are mistaken that the AHU heating and cooling coils always
> > > oppose each other. I am not familiar with the templates as I always work
> > > directly with the idf file, but if you run the expidf file, and then
> > review
> > > the full idf file created you should see a few things:
> > >
> > > 1. There should be a setpoint manager that controls the temperature of
> > the
> > > air supplied to the zones. Usually it is placed on the AirloopHVAC supply
> > > outlet node. What type of setpoint manager is it?
> > > 2. The heatin and cooling coils on the supply side of the air handler
> > loop
> > > should both have controllers.
> > > 3. The controllers will have a reference node. Is the reference node the
> > > same for both controllers? Is the reference node the same as the setpoint
> > > node for the setpoint manager you found in answering question #1? If so,
> > > the two controllers will work together to maintain the conditions at that
> > > setpoint.
> > >
> > > What I've described above is a pretty simple system. You could also have
> > a
> > > setpoint manager at the outlet o each coil specifying the temperature in
> > > multiple places. In this case you can force the coils to operate
> > > simultaneously.
> > >
> > > I hope this description helps. Good luck.
> > >
> > > --
> > > Karen
> > >
> > > On Friday, April 13, 2012, ecoeficientees <ecoeficiente@> wrote:
> > > >
> > > >
> > > > Dear James,
> > > > I am afraid that Energyplus does not control heating and cooling coil
> > > operation for a dual setpoint, at least when they are water coils (not
> > sure
> > > about DX Coils). Even VAV HVAC Template says so in the help file (that
> > you
> > > need to use availability managers to control when the coils are
> > operating).
> > > >
> > > > It is frustating, as I have said in another reply, because it seems
> > that
> > > EMS is the only solution to the problem.
> > > >
> > > > Regards,
> > > >
> > > > Germán.
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jim Dirkes" <jim@> wrote:
> > > >>
> > > >> Dear Germán,
> > > >>
> > > >> EnergyPlus will automatically control the operation heating and
> > cooling
> > > coil
> > > >> according to your SetpointManagers. It will not operate cooling and
> > > heating
> > > >> simultaneously unless you have some sort of CoolReheat control. (You
> > can
> > > >> see this is you create output variables for the temperature node
> > > downstream
> > > >> of each coil)
> > > >>
> > > >> Regarding the frost warnings, you can:
> > > >>
> > > >> · Ignore the warnings (probably this does not affect accuracy too
> > > >> much, but you will get a lot of warnings!)
> > > >>
> > > >> · Create a two-speed DX coil (This will probably reduce the number
> > > >> of warnings)
> > > >>
> > > >> · Employ EMS to prevent DX coil operation below a certain outdoor
> > > >> temperature (e.g. 10-12C)
> > > >>
> > > >>
> > > >>
> > > >> The Building Performance Team
> > > >> James V. Dirkes II, P.E., BEMP , LEED AP
> > > >> 1631 Acacia Drive NW
> > > >> Grand Rapids, MI 49504
> > > >> 616 450 8653
> > > >>
> > > >>
> > > >>
> > > >> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > >> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of
> > ecoeficientees
> > > >> Sent: Friday, April 13, 2012 9:30 AM
> > > >> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > >> Subject: [EnergyPlus_Support] Re: Heating/Setpoint Controller
> > > >>
> > > >>
> > > >>
> > > >>
> > > >>
> > > >> Hi, I am stuck on the same problem.
> > > >> Is Energyplus EMS the only way? Or which 4-5 variables can you adjust?
> > > >> Also, what do you mean by not using VAV? I am using an AHU and VAV or
> > > not,
> > > >> there is the same problem, since you have to use a Setpoint manager
> > for
> > > the
> > > >> coils.
> > > >>
> > > >> It is a very common HVAC configuration, which I cannot find how to
> > > >> configure...
> > > >> Any idea?
> > > >>
> > > >> Regards,
> > > >>
> > > >> Germán.
> > > >>
> > > >> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > >> <mailto:EnergyPlus_Support%40yahoogroups.com> , YuanLu Li <yli006@>
> > > >> wrote:
> > > >> >
> > > >> >
> > > >> > If yu do not have pre-heat and reheat and there is not need to use
> > VAV,
> > > >> you should not model using VAV. The zone thermostat should be used to
> > > >> control the cooling and heating coils directly. When you use VAV
> > dampler,
> > > >> the theremostat controls the damper which change the flow rate which
> > > results
> > > >> in different zone temperature. The process is more complex. You need
> > to
> > > >> adjust four or five variables to work together to make the system
> > work.
> > > >> ============================In a real VAV system, a computer control
> > > system
> > > >> is used to control the fan speed. Pressure sensors are also required.
> > > Duct
> > > >> temperature, diffuser temperature and room temperature are modified to
> > > make
> > > >> the desission on whaat to do. Dr. Li
> > > >> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > >> <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > >> > From: matthew.sverre.anderson@
> > > >> > Date: Thu, 10 Nov 2011 15:13:58 +0000
> > > >> > Subject: [EnergyPlus_Support] Heating/Setpoint Controller
> > > >> >
> > > >> > Hello Everybody, I have a question that likely (or at least
> > hopefully!)
> > > >> has an easy answer and I am simply too foolish to know it.
> > > >> > So I have a building which I modeled as a VAV with no reheat, and no
> > > >> preheat coil. I want the coils to operate as needed and simply ignore
> > any
> > > >> frost warnings. However, I currently have no schedule for either since
> > > there
> > > >> will be many times during the fall/spring where we might need to
> > > heat/cool
> > > >> during the same day or during the week.
> > > >> >
> > > >> > The problem I am currently having is that the heating/cooling coils
> > are
> > > >> operating year long at the same time. I want the HC to operate when
> > the
> > > >> building needs heating, the CC to operate when the building needs
> > cooling
> > > >> (neither to operate at the same time). Am I thinking about this
> > > incorrectly?
> > > >>
> > > >> >
> > > >> > Also is there a way to implement a dead band above/below the set
> > point
> > > >> where the system is "satisfied" to prevent the system from "slamming"
> > > >> on/off?
> > > >> >
> > > >>
> > > >
> > > >
> > >
> >
> >  
> >
>




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