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Re: [EnergyPlus_Support] Radiant Floor System works great!

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Radiant Floor System works great!
From: "Michael J. Witte" <mjwitte@xxxxxxxx>
Date: Wed, 29 Nov 2006 16:17:46 -0600
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Glad to hear it is working well.  Regarding an "adiabatic" ground boundary 
condition.  You can achieve a fully adiabatic condition by setting the slab 
outside face environment to "OtherZoneSurface" and setting the outside face 
environment object to be the slab (the surface "sees" itself on the other 
side).

Adding large amounts of insulation could potentially cause problems--not with 
the radiant system calculation but with the CTF calculation.  If combining high 
R-value insulation with some sort of mass, you could end up with a problem.  In 
general, the CTF solution should be able to handle this by adjusting the time 
step.  However, we haven't tried every combination.  This would need to be 
looked at.  If your are seeing a problem with the heat balance, it is much more 
likely to be a CTF problem than a radiant system problem.  Would you please 
send an example input file which shows the problem you are seeing?

Mike


On 27 Nov 2006 at 18:35, Ian Doebber wrote:

> Mike
> 
>  
> 
> Changing from Zone to Surface-Level report variables gives the correct energy
> balance.  The only other caveat to using the Radiant Floor model is the ground
> boundary condition.  Something to discuss with Rick Strand is how the solver
> handles increasing levels of insulation underneath the slab.  
> 
>  
> 
> On one extreme, the energy balance is completely off when I specify an
> adiabatic ground boundary condition.  Its as if the concrete slab absorbs
> energy and then it disappears.
> 
>  
> 
> On the other extreme, no insulation gives a perfect energy balance. 
> 
>  
> 
> With increasing levels of insulation, the energy balance becomes worse.
> 
>  
> 
> Therefore, I've specified only R-2.5 insulation underneath the slab and
> monthly ground temperatures 1 degree F underneath the interior space
> temperature.  This is as close to a adiabatic condition as possible.  The
> energy balance difference with such a small amount of insulation is
> negligible.  
> 
>  
> 
> Now, the radiant system works great, giving me an understanding of its
> capacity with different inlet/outlet temperatures, transient behavior, and
> control strategy (charging the floor and then letting it float during the peak
> hours).  The outputs are what I expect with basic knowledge of radiant systems
> from our previous experience and talking with Wirsbo, Watts Radiant, and Davis
> Energy Group.
> 
>  
> 
> Let me know your thoughts on this.  I'd be interested to hear what Rick Strand
> has to say about the boundary condition issue.
> 
>  
> 
> Thanks
> 
>  
> 
> Ian Doebber
> 
> Arup
> 
>  
> 
> ________________________________
> 
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Michael J. Witte
> Sent: Wednesday, October 25, 2006 7:45 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: RE: [EnergyPlus_Support] Further Insight : Skylight / Radiant Cooling
> Strange Behavior
> 
>  
> 
> We have confirmed that this is a reporting error just for the zone level
> window 
> heat gain/loss report variables. When radiant cooling is active, the zone 
> surface heat balance is called extra times to update the surface temperatures.
> The accumulation of Zone Window Heat Gain/Loss was not being reset to zero 
> within this loop. This will be fixed for the next release. Until then the 
> workaround is to use the surface-level Window Heat Gain/Loss report variables
> when using radiant heating/cooling systems.
> 
> Mike
> 
> On 23 Oct 2006 at 22:29, Michael J. Witte wrote:
> 
> > Digging into this further, the problem appears to be the values reported by
> > "Zone Window Heat Gain" and "Zone Window Heat Gain Energy". When the
> radiant
> > cooling is active, these zone variables do not agree with the surface
> > variables 
> > "Window Heat Gain" and "Window Heat Gain Energy". So, use the surface 
> > variables instead and I think you will find the results to be more
> > reasonable.
> > 
> > Checking the change in cooling load with and without the skylights, at hour
> > 10:00:
> > 
> > Zone Window Heat Gain = 5.53E+04
> > Window Heat Gain = 1.38E+04
> > Change in cooling load w/o skylights = 5.89E+03
> > 
> > So, this appears to be a reporting problem with the zone level window heat
> > gain 
> > report variable and not a problem in the overall heat balance.
> > 
> > Mike
> > 
> > 
> > Mike
> > 
> > 
> > On 19 Oct 2006 at 13:37, Michael J. Witte wrote:
> > 
> > > Ian: 
> > > 
> > > If you delete the skylights, does the cooling load on the radiant system
> > > change 
> > > by the same order of magnitude as the reported heat gain from the
> skylights?
> > > I 
> > > suspect this may just be a problem with the reported window heat gain
> > rather
> > > than a real heat balance problem. The reported window heat gain is just
> a
> > > side 
> > > calculation for reporting purposes, that value is not actually used in
> the
> > > heat 
> > > balance.
> > > 
> > > Mike
> > > 
> > > 
> > > On 15 Oct 2006 at 15:42, Linda Lawrie wrote:
> > > 
> > > > At 04:27 PM 10/13/2006, Griffith, Brent wrote:
> > > > >I believe this is a known bug (CR6897). But unfortunately it isn't a
> > > > >quick job and I don't think it was fixed in V1.4 (which is already
> > out).
> > > > 
> > > > As Brent says, this is a known or suspected problem. If you submit 
> > > > your file (either send direct to me or upload to the support web 
> > > > site), it may help our developer in tracking it down.
> > > > 
> > > > 
> > > > Linda
> > > > 
> > > > EnergyPlus WebSite: http://www.energyplus.gov
> <http://www.energyplus.gov> 
> > > > Owner: EnergyPlus_Support list
> > > > Member: EnergyPlus Development Team
> > > > 
> > > > 
> > > > 
> > > > [Non-text portions of this message have been removed]
> > > > 
> > > > 
> > > > 
> > > > The primary EnergyPlus web site is found at:
> > > > http://www.energyplus.gov <http://www.energyplus.gov> 
> > > > 
> > > > The group web site is:
> > > > http://groups.yahoo.com/group/EnergyPlus_Support/
> <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.idf and
> > press
> > > the
> > > > "search" button.
> > > > 
> > > > Yahoo! Groups Links
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > 
> > > 
> > > ========================================================
> > > Michael J. Witte, GARD Analytics, Inc.
> > > EnergyPlus Testing and Support 
> > > EnergyPlus-Support@xxxxxxxx <mailto:EnergyPlus-Support%40gard.com> 
> > > 
> > > 
> > > 
> > > 
> > > 
> > > The primary EnergyPlus web site is found at:
> > > http://www.energyplus.gov <http://www.energyplus.gov> 
> > > 
> > > The group web site is:
> > > http://groups.yahoo.com/group/EnergyPlus_Support/
> <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.idf and press
> > the
> > > "search" button.
> > > 
> > > Yahoo! Groups Links
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 
> > 
> > 
> > ========================================================
> > Michael J. Witte, GARD Analytics, Inc.
> > EnergyPlus Testing and Support 
> > EnergyPlus-Support@xxxxxxxx <mailto:EnergyPlus-Support%40gard.com> 
> > 
> > 
> > 
> > 
> > 
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov <http://www.energyplus.gov> 
> > 
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> <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.idf and press
> the
> > "search" button.
> > 
> > Yahoo! Groups Links
> > 
> > 
> > 
> > 
> > 
> > 
> 
>  
> 
> ____________________________________________________________
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> 
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
> 
> The group web site is:
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> 
> 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.idf and press the
> "search" button.
>  
> Yahoo! Groups Links
> 
> 
> 
> 
> 


========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx





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References:
- [EnergyPlus_Support] Radiant Floor System works great!
  - From: Ian Doebber

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