[EnergyPlus_Support] Re: LOW TEMP RADIANT SYSTEM shut-off

["Florian Stift" <florian.stift@xxxxxxxxx>]

Michael,

Thank you for your really clarifying answer!
I understand the shut-off because of condensation at the ceiling surface!

My problem is actually to get that stream of air into the zone. As I
described, I tried using the Purchased Air object but other users
stated that this system is meant to be used alone!!

Is there any other system which can provide 0,5ACH with 22deg.C
continuously for the zone which can be input in E+ with not too much
time effort?
I am asking because I wanted to avoid defining a whole Air System for
a single zone. 

Best Wishes,
Florian


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte"
<mjwitte@...> wrote:
>
> Posting this message on behalf of Rick Strand (not clear if his
original 
> post was distributed to the list):
> 
> Florian:
> 
> The low temperature radiant system is designed to shut-off when it 
> predicts that condensation is a possibility at the surface that is part 
> of the system.  Inside the program, the procedure works as follows.
 The 
> radiant system turns on based on availability and controls.  This leads 
> to a calculation of a new surface temperature for the surface that is 
> associated with the radiant system.  If the dew-point temperature of
the 
> zone is within 1C of the predicted surface temperature, the radiant 
> system shuts down due to the potential for condensation.  The error 
> messages should be letting you know both the predicted surface 
> temperature and the zone dewpoint temperature.
> 
> Unfortunately, with the current configuration of the low temperature 
> radiant model, the shut-off cannot be "turned off".  In other words, 
> there is no way around this as the condensation of moisture is not 
> desirable from either a modeling or a realistic standpoint.  The best 
> approach is to do exactly what you attempted to do: add an air
stream to 
> attempt to dry out the space.  I would also recommend looking at the 
> humidity levels within the space.  I have seen in several files that 
> contain radiant systems that the moisture levels rise significantly 
> because the user did not add any infiltration.  When people are in a 
> space, there is no infiltration, and a radiant system is being used, 
> people add moisture to the space, but there is no mechanism for
moisture 
> to leave the space.  What happens is that moisture levels rise to 
> saturation and the radiant system is not able to turn on at all.  So, 
> you might want to check this in your file.
> 
> I hope this helps.  Please let us know if you have further questions or 
> comments about the radiant model or EnergyPlus.
> 
> Thanks,
> 
> Rick Strand
> EnergyPlus Development Team
> 
> Florian Stift wrote:
> > Dear E+Users,
> > 
> > I am simulating a single zone which is cooled by a "LOW TEMP RADIANT
> > SYSTEM"!
> > I wanted the system to be continuously "ON", so I defined a very low
> > zone cooling setpoint, like 2degC. 
> > 
> > When I was realising that the system shuts off when condensation
> > occurs on the inside of the ceiling surface, I added a Purchased Air
> > System to serve the zone with a limited amount of conditioned air,
> > e.g. 0,5ACH with 22deg.C.
> > 
> > There is no condensation any more but the LOW TEMP RADIANT SYSTEM
> > shuts off when the zone air temperature falls below that 22degC from
> > the Purchased Air Schedule, but I still have defined that schedule for
> > a Setpoint of 2degC.
> > 
> > How can I manage to tell the LOW TEMP RADIANT SYSTEM to be ON all the
> > time??
> > 
> > Thanks in advance for any help!
> > 
> > Best Wishes,
> > Florian
> > 
> > 
> > ------------------------------------
> > 
> > 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
> > 
> > 
> >
>



------------------------------------

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