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[EnergyPlus_Support] Re: Problem with removing reheat coils in VAV
Many thanks for your help, but I still have the same problem.
I changed the scheduled setpointmanager for the singlezone:heating, but it made no difference.
What I did was this:
- opened the example file "HVACTemplate-5ZonePackagedVAV.idf" with the Chicago weather file;
- changed the thermostat so that the interior temperature should be between 20-25ºC (with the reheat coils active the temperature stays in this limit, so the problem is not from here);
- removed the reheat coils and the cooling coil;
- removed all the lights and electric equipment and most of the people (just to eliminate the influence of internal heating loads);
- changed the heating design temperature from 10ºC to 40ºC;
- deleted the SetpointManager:Scheduled for Heating and created the SetpointManager:SingleZone:Heating, using the Space3-1 as the control zone name (it's the zone with more heating demands).
And then the temperatures of Space3-1 (and others) are not hot enough. What else can be wrong? Could the problem be in the setpointmanager: MixedAir ?
Thanks in advance!
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad <RRaustad@...> wrote:
>
> If you remove the terminal unit heating coils, you can no longer control
> the air loop heating coil at a constant supply air temperature (i.e.,
> using a scheduled temperature set point). Verify how the main heating
> coil is controlled (i'm guessing scheduled) and use a different type of
> set point manager to control it (e.g., SetpointManager:SingleZone:Heating).
>
> On 7/11/2011 7:01 PM, n_junk wrote:
> >
> >
> > Hi! You are refering to "Central Heating Design Supply Air
> > Temperature", right? I forgot to tell that I already had changed it to
> > 20, 30, 40, 50 and even 70ºC and none of them hadn't change at all the
> > interior temperature. If I use a high temperature and put again the
> > reheat coils, the rooms sometimes even overheat, but without them the
> > temperatures continues under 20ºC.
> >
> > This is really odd, I don't know what is happening.
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, Vinay Devanathan
> > <vinay.devanathan@> wrote:
> > >
> > > The main heating coils setpoint temperature will be set such that it
> > only
> > > heats air to a certain temp, (say around 15 - 16 C), so that the reheat
> > > coils can be sized for proper capacity to meet the load. When you
> > remove the
> > > reheat coils, your supply air will obviously be under-heated as the main
> > > heating coil is not sized for that high capacity and will end up
> > providing
> > > supply air at the setpoint temperature. You can look at what the heating
> > > coils design leaving air temperature by viewing the expidf file under
> > > Sizing:System object.
> > >
> > > On Mon, Jul 11, 2011 at 1:02 PM, n_junk@ <
> > > n_junk@> wrote:
> > >
> > > > **
> > > >
> > > >
> > > > Hi!
> > > >
> > > > I'm trying to simulate an existing HVAC system which is similar to
> > a VAV,
> > > > only with heating, without cooling coil or reheat coils. I'm using
> > the HVAC
> > > > Template VAV Packaged.
> > > > The rooms' temperatures stay above 20ºC, like I configured in the
> > > > Thermostat, until I remove the reheat coils. When I do that the
> > temperature
> > > > drops under 20ºC and only reaches it if there are internal loads.
> > > >
> > > > I have almost everything in autosize, except the maximum flow of
> > the input
> > > > air (but autosize never reaches it, so I think the problem is not from
> > > > there).
> > > >
> > > > To see my problem just open this example file that comes with
> > EnergyPlus:
> > > > HVACTemplate-5ZonePackagedVAV.idf. Then run a simulation and
> > consult the
> > > > evolution of Zone Air Temperature for any of the conditioned zones
> > and see
> > > > that it stays inside the temperatures of the Thermostat. After
> > that go to
> > > > the file, remove the reheat coils of every zone (and deactivate
> > the system
> > > > cooling coil), run the simulation again and compare the
> > temperatures. You'll
> > > > see that now the temperatures stay under the Thermostat limit and
> > only reach
> > > > it when the internal loads harm the room enough.
> > > >
> > > > I'm looking in the expidf file for days and I still don't know what is
> > > > wrong with it. Since I really have to remove the reheat coils,
> > what can I do
> > > > to correct this problem?
> > > >
> > > > Thanks in advance!
> > > >
> > > >
> > > >
> > >
> >
> >
>
> --
> 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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