Re: [EnergyPlus_Support] Re: autosizing components in hybrid DV/radiant heating system

On Wed, Dec 2, 2009 at 11:06 AM, Phylroy <phylroy.lopez@xxxxxxxxx> wrote:

Hey Josh,

I'm interested in the solution that you guys worked out. I'm working on a similar model. Was this resolved?

Phylroy

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Josh K" <jeemang@...> wrote:
>
> Hi Fred;
>
> Thanks in advance for taking a look at it. I uploaded the .idf to the
> Problem_Submittals folder. It's called "DV_test."
>
> Thanks,
>
> Josh
>
>
> On Nov 20, 2007 3:56 PM, Fred Buhl <wfbuhl@...> wrote:
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > josh_miarch wrote:
> > > I'm attempting to model a cold climate system in which heating is
> > > provided by a combination of centrally conditioned air (delivered via
> > > displacement ventilation) and a radiant panel. The zone in question
> > > has a constant setpoint of 21 C. Air is delivered from the central AHU
> > > at 19 C, with the balance of the heating load being made up by the
> > > radiant panel.
> > >
> > > I've modeled this with a DIRECT AIR object given heating priority 1
> > > and a LOW TEMP RADIANT SYSTEM:HYDRONIC object (heating control
> > > temperature = 18 C, throttling range = 3 C) given heating priority 2.
> > >
> > > The problem I'm having is that the autosizable fields of several
> > > objects are being filled incorrectly. For example, the maximum hot
> > > water flow of the radiant panel is being autosized to 0. Strangely, I
> > > noticed that when I increase the "zone heating design supply air
> > > temperature" field in the ZONE SIZING object from its original value
> > > of 19 C, at a certain point the maximum hot water flow of the radiant
> > > panel starts getting autosized to numbers greater than 0.
> > >
> > > Investigating this further, I noticed that the "DesLoad" outputted in
> > > the "Zone Sizing Information" section of the .eio output file changed
> > > when I changed the zone heating design supply air temperature in the
> > > ZONE SIZING object. For example, when the design supply air temp was
> > > set to 19 C, the "DesLoad" was 0.20703 W, and when it was set to 80 C,
> > > the "DesLoad" was 13194 W.
> > >
> > > I'm guessing that this is the source of my problems. It seems strange
> > > to me that the design load would change based on the supply air
> > > temperature -- shouldn't these variables be independent of one another?
> > >
> > Yes; in theory anyway. But other design constraints might be affecting
> > the initially calculated, pure
> > design load. Why don't you upload your input and we will take a look.
> >
> > Fred Buhl
> >
> > > I know that EnergyPlus can sometimes struggle with hybrid systems like
> > > this; I'm wondering if there is an error on my part, or if this an
> > > example of EnergyPlus' limitations in this area. Any advice that
> > > anyone could give me that would get me closer to an accurate
> > > simulation would be greatly appreciated.
> > >
> > > Thanks,
> > >
> > > Josh
> > >
> > > --
> > > Josh Kjenner, EIT, LEED AP
> > > Manasc Isaac Architects Ltd.
> > > 10225 100 Avenue :: Edmonton, AB T5J 0A1
> > > 780.429.3977
> > >
> > >
> > >
> > >
> > >
> > > The primary EnergyPlus web site is found at:
> > > http://www.energyplus.gov
> > >
> > > The group web site is:
> > > http://groups.yahoo.com/group/EnergyPlus_Support/
> > >
> > > Attachments are not allowed -- please post any files to the appropriate
> > folder in the Files area of the Support Web Site.
> > >
> > > EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the
> > Documentation link and press the "search" button.
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> >
>
>
>
> --
> Josh Kjenner, EIT, LEED AP
> Manasc Isaac Architects Ltd.
> 10225 100 Avenue :: Edmonton, AB T5J 0A1
> 780.429.3977
>