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[EnergyPlus_Support] Re: Problem with removing reheat coils in VAV
Without looking at the idf, I would guess you've forgoten to define the Controller for your additional water:coil which is required. Make sure you also have a SetpointManager for the extra coil. Since your templates are probably producing unitary systems, like in the previous idf, be aware that although you may disable the gas or electric coil, the unitary object will still be placing setpoints on specific nodes. A tip is to monitor that. Find the relative output variables in the rdd file and request them in the idf. Do you have an xesoview to view results?
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
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> Hi, I have tried your IDF. The sever error was caused by: Controller:WaterCoil="DXVAV SYS 1 HEATING COIL CONTROLLER" not found. I have no idea where this object is used in the plant loop yet. The object is in the IDF and why it is not found.==================== If you want to use this configuration for your final design, you should look at the system node values using the IDF I retuned to use. Use the DesignDay sizing to save time. Use time step display on spread sheed for finer resolutin of values. The Summer and Winter zone temperatures are plotted on the chart enclosed. The setpoint temperatures were 10 and 16 °C. If you move the heating setpoint up, the heater will be turned on in Winter. This is how I analysis and make the next move.. Dr. Li
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: n_junk@...
> Date: Mon, 18 Jul 2011 17:21:36 -0700
> Subject: [EnergyPlus_Support] Re: Problem with removing reheat coils in VAV
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> Hi,
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> With the things that you said in mind, I tried some solutions and I solved a part of the problem, removing the autosize for the Heating Design Air Flow Rate and inserting a constant value. That forced the heating of the zones. Of course there are still some strange values but I know that it just needs some tweaking.
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> The problem now is that I don't want a heating coil of gas, like the current one that is on the system, I need to simulate a heating coil of (hot) water, and when I change the heating coil from gas to water the zones' heating rolls back to where they were, malfunctioning again. I then installed an extra electric heating coil after the water heating coil and then the heating worked with no problems. I think that with this I prove that the problem is coming from the
> water or plant loop.
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> But I don't know what is specifically going wrong. If you analyze the results spreadsheet you will see that the water enters the heating coil and leaves it without changing its temperature. It's like the heating coil is not functioning at all. More strange than that is that the program is autosizing it anyway. I can't understand how something that doesn't work has a calculated heating capacity.
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> I will try to attach the new file. Note that it will go with the electric heating coil, with the schedule "always off". To activate it just change the schedule. Sorry in advance if any of the values are misleading or the names are not very simple or if they are badly defined. It's just very difficult to me to mantain all this variables in control with so much changes and I'm really tired from being days and nights trying to solve this.
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> My biggest questions are, at this moment, is there a way to change the priority of the
> heating coils? And second, what I'm doing wrong in the boiler, hot water loop or heating coil? Remember that I'm a rookie in EPlus, so check first for a basic error or common mistake.
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> Once again many thanks to you. Without your help in this last days I couldn't go any further!
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> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "n_junk" <n_junk@> wrote:
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> > You gave me a lot to think, many thanks! I got some ideas that might work. I will keep you posted with the results.
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> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@> wrote:
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> > > Hi, Lixeira I assume that the IDF you used was HVACTemplate-5ZonePackagedVAV.idf
> > > The following was extract from the expIDF without your editing.ã??
> > > =============================ã??
> > >
> SetpointManager:Scheduled, DXVAV Sys 1 Cooling Supply Air Temp Manager, !- Name Temperature, ! Control Variable HVACTemplate-Always 12.8, ! Schedule Name DXVAV Sys 1 Supply Fan Outlet; ! Setpoint Node or NodeList Name
> > >
> > > The template program has generated a schedule for you and used the temprature 12.8 C for the cool air output of the system.Because this is low compared with the zone thermostat setting, the reheat coil is uded to heat the zone to the required temperature. Find this compact schedule in your expIDF and change it to 22 or 23°C. and rename it
> to IDF with a diffeent name. The reheat coil should stop working. You can also change the reheat coil avilability schedule to always OFF. Then the zone will be cold, unless you turn on more lights. This is another way to test the program, with your own added heating. If the reheat power is 1000 watt, add 1100 watt to your lighting would turn off the reheat of that zone.==========SetpointManager:MixedAir, DXVAV Sys 1 Cooling Coil Air Temp Manager, !- Name Temperature, ! Control Variable DXVAV Sys 1 Supply Fan Outlet, ! Reference Setpoint Node Name DXVAV Sys 1 Heating Coil Outlet, ! Fan Inlet
> Node Name DXVAV Sys 1 Supply Fan Outlet, ! Fan Outlet Node Name DXVAV Sys 1 Mixed Air Nodes; ! Setpoint Node or NodeList Name
> > >
> > > This manager defines the fan locatin and the mixed air node to be controlled to the temperature in the schedule which was set to 12.8.=================! NOTE: Heating supply air setpoint is placed on Supply Path Inlet node to allow separate heating and cooling setpoints.
> > > ! SetpointManager:MixedAir <system name> Heating Coil Air Temp Manager adjusts this setpoint for fan heat and places it on the Heating Coil Outlet
> > >
> > > This note explains why you have two MixedAir managers. Draw a diagram to see where these nodes are in the air loop system. SetpointManager:Scheduled,
> > > DXVAV Sys 1 Heating Supply Air Temp
> Manager, !- Name Temperature, ! Control Variable HVACTemplate-Always 10, ! Schedule Name DXVAV Sys 1 Supply Path Inlet; ! Setpoint Node or NodeList Name
> > >
> > > SetpointManager:MixedAir, DXVAV Sys 1 Heating Coil Air Temp Manager, !- Name Temperature, ! Control Variable DXVAV Sys 1 Supply Path
> Inlet, ! Reference Setpoint Node Name DXVAV Sys 1 Heating Coil Outlet, ! Fan Inlet Node Name DXVAV Sys 1 Supply Fan Outlet, ! Fan Outlet Node Name DXVAV Sys 1 Heating Coil Outlet; ! Setpoint Node or NodeList Name
> > >
> > > Because this is set to 10°C, the reheat heater is used to heat the zone to 20°C. So change this to 19°C may stop the reheat.The temperature are normally set this way so that indivitual zones can have its own make up heating source. ========================Controller:OutdoorAir, DXVAV Sys 1 OA Controller, ! Name DXVAV Sys 1 Relief Air Outlet, ! Relief Air Outlet Node DXVAV Sys 1 Air
> Loop Inlet, ! Return Air Node Name DXVAV Sys 1 Mixed Air Outlet, ! Sensor Node Name DXVAV Sys 1 Outside Air Inlet, ! Actuated Node autosize, ! minimum outside air flow rate {m3/s} autosize, ! maximum outside air flow rate {m3/s} DifferentialDryBulb, ! Economizer Control Type
> ModulateFlow, ! Economizer Control Action Type 19, ! Fixed Dry Bulb Temperature Limit {C} , ! Fixed Enthalpy Limit {J/kg} , ! Fixed Dew Point
> Temperature Limit (C) , ! Electronic Enthalpy Limit Curve Name 4, ! Dry Bulb Temperature Lower Limit {C} NoLockout, ! Lockout Type ProportionalMinimum, ! Minimum Limit Type Min OA
> Sched, ! Minimum Outdoor Air Schedule Name , ! Minimum Fraction of Outdoor Air Schedule Name , ! Maximum Fraction of Outdoor Air Schedule Name
> ; ! Mechanical Ventilation Controller Name This controller has economizer action. When the outdoor air is between 3 to 19°C, the outdoor air can be used for air temperature adjustment.======================
> > >
> > > Hope this will help to explain how the setpoint managers work in your IDF. Dr. Li
> > > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > From: n_junk@
> > > Date: Sun, 17 Jul 2011 01:23:15 +0000
> > > Subject: [EnergyPlus_Support] Re: Problem with removing reheat coils in VAV
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> > > Hi Dr. Li,
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> > > Many thanks for your assistance!
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> > > I'm trying to analyze what you've said and see what I can change in my file.
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> > > Since it's my first simulation in energyplus, I'm still trying to learn the basics.
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> > > One thing that it's very odd to me and I can't understand at all it's the behavior of the heating coils of the system. I really don't know what is controlling them, in the program. Everytime I
> deactivate (not remove, just shut them off) the reheat coils in the zones, the heating coil of the main system seems to just turn off, even if I put setpoints in the heating coil outlet temperature or rise the design temperature. It's like the program quits to care about controlling the setpoint temperatures I inserted everytime I shut off the reheat coils.
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> > > I was expecting something far more easy and simple, that when I removed the reheat coils the program would 'think': «ok, since I can't rely anymore on the reheat coils, I need to heat more the air in the system's heating coil, so I will rise the heating coil's capacity». If I'm just shutting off the reheat coils, and not removing anything, and even rising the "heating coil design setpoint" in the HVACTemplate:System:PackagedVAV, what is going so wrong that shuts off or undersizes the heating coil's capacity, makes the setpoint temperatures
> not being met and doesn't heat the zones as expected?
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> > > Please note again that I'm still learning the basics of EnergyPlus and I'm using the HVACTemplates as a starting point, and then editing the expidf file, because it would be impossible to me to design all the air, system and plant loops, with my current knowledge, in time to deliver my thesis.
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> > > Once again, thanks in advance!
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> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@> wrote:
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> > > > Hi, Lixeira I think you are trying to replace the usual air loop with one master zone thermostat control with one which uses the set point manager to control the air loop temperature and variable damper at the
> zone without reheat coil. In this way all thermostat are available in each zone. Because you are using setpoint manager for the air loop, the temperature should not be a range, but one temperature slightly below the wanted zone temperature. This difference is normally compensated by reheat. The heating should also be slightly lower. The type 4 dead band should also be maintained at the zone, with modified schedules. When the OA is cool in Summer, your system is turning on the heater to keep the temperature at the zone thermostat setting.
> > >
> > > > There is no severe error. Just need some tuning on the available schedules and set point values or managers. AirTerminal:SingleDuct:VAV:NoReheat, should not be running at constant mode. I do not know how to change this yet. What I did of my own project was to use the one with reheat and disable the coil, not removing it, so that the damper
> will still have control of the air flow. Because the zone demand loads are not the same and dampers are not controlled, therefore the temperatures are all different. Dr. Li
> > >
> > > > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > >
> > > > From: n_junk@
> > >
> > > > Date: Sat, 16 Jul 2011 09:39:20 -0700
> > >
> > > > Subject: [EnergyPlus_Support] Re: Problem with removing reheat coils in VAV
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> > > > Hi Jean,
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> > > > I'm sending the file that I'm testing as an e-mail attachment. I hope that the attachment will be send and received without errors.
> > >
> > > > Note that the "plenum" temperatures are not controlled, but all the "spaces" temperatures should
> be controlled (always above 20ºC).
> > >
> > > > Could the problem be in the VAV terminal damper position?
> > >
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> > > > Thanks in advance!
> > >
> > > >
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> >
>
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