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[EnergyPlus_Support] Re: Time Set Point Not Met - Radiant Floor Heating System

The following has come to my attention:

This area will be clarified when the new version of 90.1 is released next month. New for the 2010 version of 90.1 are the following definitions and addition to Table G3.1

****************************************

unmet load hour: an hour in which one or more zones is
outside of the thermostat setpoint plus or minus one half of the
temperature control throttling range. Any hour with one or
more zones with an unmet cooling load or unmet heating load
is defined as an unmet load hour.

temperature control throttling range: The number of degrees
that room temperature must change in order to go from full
heating to no heating or from full cooling to no cooling.

Temperature and humidity control setpoints and schedules as well as temperature control throttling
range shall be the same for proposed and baseline building designs.


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "jeannieboef" <jeannieboef@...> wrote:
>
> Thanks, James. In my system it's not much, but when a window opens and the air temperature changes by 1.5 Kelvin, the Radiant Floor System just can't keep up because of it's huge thermal capacity. I don't have start up problems because the system is always on (actually read a study on this, which shows very small savings by ramping up and down overnight). Obviously, increasing the capacity of the system can only improve things by a negligable degree. The as designed system is also AS DESIGNED and thereby has this inherent property. It's not so much I'm taking about in any case. 1 Kelvin tolerance instead of 0.2 would probably cut it.
> 
> I've posted this question on some diverse blogs to see what people say and will keep you posted.
> 
> Thanks again for the input.
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "James V Dirkes II, PE" <jim@> wrote:
> >
> > Dear Jeannie,
> > 
> >  
> > 
> > This criteria comes from ASHRAE 90.1 ,as you probably know.  ASHRAE 90.1
> > does not define this value, although I think perhaps they should.  Since
> > they do not, I suspect that it�s up to some interpretation.
> > 
> >  
> > 
> > Normally, my �unmet loads� are at startup periods and do not last for more
> > than an hour or so.  In my opinion, this is not too important, since you can
> > always start the system a bit earlier on the coldest or hottest days.  I
> > suspect that ASHRAE�s underlying rationale for not having too many unmet
> > load hours was that they did not want the system deliberately undersized.
> > If you can justify that it�s not (deliberately undersized), you may be OK.
> > 
> >  
> > 
> > p.s., This is my opinion only.  I have not debated the issue on a LEED
> > certification!
> > 
> >  
> > 
> > The Building Performance Team
> > James V. Dirkes II, P.E., LEED AP
> > 1631 Acacia Drive NW
> > Grand Rapids, MI 49504
> > 616 450 8653
> > 
> >  
> > 
> > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of jeannieboef
> > Sent: Wednesday, September 29, 2010 2:25 AM
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > Subject: [EnergyPlus_Support] Time Set Point Not Met - Radiant Floor Heating
> > System
> > 
> >  
> > 
> >   
> > 
> > Time Set Point Not Met Tolerance is 0.2�C ( ... DOE had specified a
> > tolerance of +-0.5F for this...energyplus has a default of 0.2 degC). Am I
> > justified in relaxing this tolerance on a system that obviously cannot
> > respond to fast and so accurately to flux in room temperature? Increasing
> > the "Capacity" of the system will not fix this.
> > 
> > Should I then relax the tolerance on the baseline heating system also?
> >
>




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