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[EnergyPlus_Support] AirTerminal:SingleDuct:Uncontrolled
Hello,
I am still having difficulties getting the zone mean air temperature to be in between 20/25ºC.
I have uploaded my file to: http://f1.grp.yahoofs.com/v1/8PORTcXxquOkptvCGn4RT_g2_-onlo16igVWTVOZJqp2RmK3Qz3Snv9JjWlK_LakToGfUT0RIplNCuihQQirEbVi1N6cPStG3S7E/_Problem_Submittals/bloco_3_SigleDuctUncontrolled_WaterCoils.zip
For simplifying the problem and making the simulation faster, I have a daily output, 1 timestep per hour. No internal gains. I am only analyzing 1 zone.
I have an AHU with mixing box + cooling coil + heating coil + supply fan, in that order. I am only conditioning 1 zone so that I may understand the workings of Energy Plus. I have used the "AirTerminal:SingleDuct:Uncontrolled".
The system is mainly on "autosize".
In the file the zone is "8274".
I have tried various settings on the setpoint managers for the water coil controllers, and various zone and system size settings, but no luck getting zone temperatures to be in between 20ºC to 25 ºC.
Previously I have setup DX cooling and gas fire heater and was successful in getting the zone mean air temp. to 20/25ºC. But in evolving the system to water coils, I cannot get it to cooperate. I have seen the example files, but I didn't find a similar example. There are some VAV system examples, in which I first got to studying Energy Plus and I could set up the zone thermostat to 20/25ºC.
Can someone please explain what is it that I am missing? I need to figure this out, because then I will be applying heat recovery devices and study them more closely for my thesis.
Thank-you
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
>
>
> I do not understand why you need to monitor the zone inlet temperature manually.
>
> AirTerminal:SingleDuct:Uncontrolled is a fixed damper. It is used to split air flow from one AHU to many Zones.
> The air flow through each damper is part of a total air flow of the fan capacity.
>
> One of these is used for each Zone, one of the first listed zone is the master zone. The thermostat of this zone controls the temperature of the AHU. The AHU is normally a heating coil, a cooling coil and a fan. The out let feeds a splitter to connect all the ATU and the zones. The zone return air are combined in a plenum/mixer to the OA mixer, if used. The mixed air node of the OA mixer feeds the inlet node of the AHU.
>
> There are many examples for this Primary air loop configuration. Start with a DX cooling, gas fire heater, the system is very simple.
>
> If you must use water coils, then replace the DX and gas heeter coils with two complete HW and Chw plant loops.
>
> You may have problems with the plant loops, because the supply pump, (boiler/chiller) pipes, splitter, demand branches, mixer, must be in the right order as the branch list.
> =============================
> I usually advise my students to do simulation at the debug stage using the PurchasedAir system. (IdealLoadSystem)
> This in fact will give you all the information on the building zones, such as solar load, internal loading, heating/cooling demand, etc.
> ====================
> "Lets say a have a AHU, no zone reheat. The AHU must handel the loads, so room mean air temperature is 20ºC to 25ºC year-round. "
>
> If you are using a four-pipe two-coils with fan as the AHU per zone, it is very easy.
>
> Use a type 4 thermostat control for the zone. Set the heating setpount to 20°C and cooling setpoint to 25°C. The zone between 20° and 25°C is the dead band, within which neither the cooling and heating system will turn on for that zone. This mean you need not control the water boiler and/or chillers, and leave them on all the year a round.
>
> Use district cooling and heating and it will be very easy to find out what is the building heating and cooling load.
>
> The thermostat controlls the coils, if the fan is constant speed.
> ========================================
> "The system is mostly on "autosize" so there are no limitations to coil and fan capacities. " This statement is not always true. It depends on how you use them. If you do not have a properly designed sizing object and sizing data, the autosize will not know what you have in the building.
>
> ==================================
> "I have no internal gains setup. I am studying these option for my thesis in with i will have to simulate an AHU. Please can someone point me in the right direction? I am not seeing what is missing."
>
> Earlier, you said, What option must i choose?
> > > Air:Terminal:SingleDuct:Uncontrolled?? if i choose this i think i cannot define de air Branch;
> > > Or should i look into NaturalVentilationAndDuctLeakage for the system? but this does not allow the choise of a variable fan.
>
> Air:Terminal:SingleDuct:Uncontrolled is a fixed damper, to be used one per zone, and must have aa AHU to provide the air flow.
>
> AirTerminal:Singleduct:VAV:NoReheat is a controlled damper. Because all the dampers may be closed, the AHU may need an air by-pass path to keep the duct temperature constant.
>
> NaturalVentilationAndDuctLeakage is too advanced for you. It require the knowledge on AFN (air flow network).
>
> A variable speed fan is not a VAV (Variable air volume). ADU with VAV is a controlled damper,
>
> Reheat coil in ADU is used for humidity control with cooling, and can be used also for heating without cooling.
>
> The choice of a system depends on how much control is required, when the load is varied in zones on the same system.
> ============================
> To clarify: "Basically I want to simulate an Air Handling Unit with pre-heat, cooling
> > > and heating coil (all water), mixing box and a variable fan. No terminal reheating."
>
> What is pre-heat? Heating the outside air before the inlet of the OA mixer? This is a more advanced configuration. You need to define what air or power source is used for pre-heating.
>
> The missing information is: One fan coil unit per zone or One AHU feeding a number of zones.
>
> For the second option using VAV zone ADU, you may not use type 4 thermostat, because the AHU cannot heat and cool at the same time, unless you have separate hot and cool air in two ducts.
>
> You need to decide first, what you wanted to study with the simulation result. Posting your IDF may provide more information on what you are trying to do.
>
> Dr. Li
>
>
>
>
>
>
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: vieira.jose99@...
> Date: Fri, 25 Mar 2011 15:01:41 +0000
> Subject: [EnergyPlus_Support] Re: AirTerminal:SingleDuct:VAV:NoReheat
>
>
>
>
>
>
> Thank-you for your help. I have been trying all day now the AirTerminal:SingleDuct:Uncontrolled but still cannot set up it so room temperatures ar at minimum 20ºC maximum 25ºC. I have tried a few options on the setpoint manager and cannot get to the minimum temperture in winter.
>
> Lets say a have a AHU, no zone reheat. The AHU must handel the loads, so room mean air temperature is 20ºC to 25ºC year-round.
>
> I have tried using a controller for the heat and cool water coils, but have to define a "zone inlet node" temperature setpoint(or a splitter inlet node temperature setpoint), this is where I have problems, I want that node temperature to get automatically set depending on room temperature and its thermostat. But when using a controller for these coils i must set setpoint temperatures for them.
>
> I have tried the system without the cool and heat water coil controllers, and run the simulation, but still cannot get 20/25ºC.
>
> The system is mostly on "autosize" so there are no limitations to coil and fan capacities.
>
> I have no internal gains setup. I am studing these option for my thesis in with i will have to simulate an AHU. Please can someone point me in the right direction? I am not seeing what is missing.
>
> Thank-you all for helping
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, x z <xs.zhang.2010@> wrote:
> >
> > Hi Vieira,
> >
> > I had the same issues when I was debuging my model with
> > AirTerminal:Singleduct:VAV:NoReheat or AirTerminal:SingleDuct:Uncontrolled.
> > (I used AirTerminal:SingleDuct:Uncontrolled)
> >
> > There is tricky question whether you have one air-handler serving one zone
> > or multiple zones. If multiple zones, you may risk that your AHU's supply
> > air condition satisfy one zone's heat load but may not meet other zones'.
> > You can try some SetpointManger for your supply air condition. It really
> > depends on your zones' heat load profile
> >
> > If only one zone per AHU. Then you should be able to get your zone
> > temperature under control by using SetPointManager:WrmestTemperatureFlow or
> > some others for your supply air condition. Basically, you give the lowest
> > (cooling) and highest (heating) supply air condition. Then the system will
> > determine the SAT based on your load condition
> >
> > Another thing to check is your thermostat. Sometime your temperature is
> > seating between the deadband. Properly setup the deadband or simply use
> > control type 1 or 2 if you heating/cooling need is simple may also help
> >
> > XS
> >
> > On Thu, Mar 24, 2011 at 11:09 AM, vieira.jose99 <vieira.jose99@>wrote:
> >
> > >
> > >
> > > I have verified that i cannot create a AirTerminal:Singleduct:VAV:NoReheat
> > > to get zone temperatures in between 20/25 ºC. I have to define a controller
> > > to the heating and cooling coils (both water) of the air handeling unit then
> > > that makes me define setpoint air temperatures of the air entering the zone.
> > >
> > > Even if i delete the heat coil controller, the zone temperature in winter
> > > does not reach 20ºC.
> > >
> > > Basically I want to simulate an Air Handeling Unit with pre-heat, cooling
> > > and heating coil (all water), mixing box and a variable fan. No terminal
> > > reheating.
> > >
> > > What option must i choose?
> > > Air:Terminal:SingleDuct:Uncontrolled?? if i choose this i think i cannot
> > > define de airBranch;
> > > Or should i look into NaturalVentilationAndDuctLeakage for the system? but
> > > this does not allow the choise of a variable fan.
> > >
> > > Thank-you
> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad <RRaustad@>
> > > wrote:
> > > >
> > > > Sounds like you need to include a heating coil in the air loop when
> > > > using AirTerminal:Singleduct:VAV:NoReheat. I you already have one then
> > > > you are not controlling it correctly or the zone loads are so diverse
> > > > that some will wind up below 20C. This can sometimes be corrected by
> > > > balancing the air loop flow rates to each zone (i.e., giving more flow
> > > > to colder zones and less flow to warmer zones).
> > > >
> > > > The supply air reset schedule is used to minimize heating energy in
> > > > winter. If you kept the same cold supply air temperature all year
> > > > around, the heating coils would have to work harder in the winter.
> > > >
> > > > On 3/24/2011 5:47 AM, vieira.jose99 wrote:
> > > > >
> > > > > AirTerminal:SingleDuct:VAV:NoReheat
> > > > >
> > > > > I have set up everything, but I want the mean air temperature to be in
> > > > > between 20 and 25ºC. But this does not happen. I have the thermostats
> > > > > configured to be 20/25ºC.
> > > > > The mean air temperature just stays a few degrees above the outside
> > > > > air temperature.
> > > > > I have the coils, boiler and chiller on autosize.
> > > > >
> > > > > When I configure the same setup to AirTerminal:SingleDuct:VAV:Reheat
> > > > > with reheat coils on autosize, I get it to be in between 20 and 25ºC.
> > > > >
> > > > > Any advice?
> > > > >
> > > > > Also....can someone explain what is the "Seasonal Reset Supply Air
> > > > > Temp Sch" for? I have read the inputoutput, but still cannot
> > > > > understand the basics of this schedule.
> > > > >
> > > > > thank-you
> > > > >
> > > > >
> > > >
> > > > --
> > > > 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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