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[EnergyPlus_Support] Re: Heating/Setpoint Controller
I also usually have this problem. There are a few solutions.
1) The one is to control the exit temp of the cooling coil at the exit so that when the zone calls for cooling you deliver cold air. Since the heating coil follows the cooling coil, it now sees really cold air comming in and looks at the outlet of the heating coil temp, compares to the zone temp and would usually try to heat this...to help with this issue you could employ the following controller on the heating coil to minimize coil fighting. This uses a sliding scale for the coil exit temp on the heating coil.
SetpointManager:SingleZone:Heating,
118129 Heating Supply Air Temp Manager, !- Name
Temperature, !- Control Variable
-99., !- Minimum Supply Air Temperature {C}
32., !- Maximum Supply Air Temperature {C}
118129, !- Control Zone Name
118129 Zone Air Node, !- Zone Node Name
118129 Zone Equip Inlet, !- Zone Inlet Node Name
118129 AHU Air Loop Outlet; !- Setpoint Node or NodeList Name
At the same time you want to maximize cold outdoor air when it is preverable to do so, which means using econimizer control at the mixing box. Here the control reference node could also be shifted. Note: you can't use the same node twice for control.
PS Control with DOAS is often a bit tricky, I found.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "ecoeficientees" <ecoeficiente@...> wrote:
>
> 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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