Re: [EnergyPlus_Support] Re: Warmup convergence

[Linda Lawrie <linda@xxxxxxxxxxxxxx>]

I suggest you read the descriptions in the Eng Ref and IORef
about this.  We instigated a study a few years ago and determined
the suggested number of "minimum iterations" before convergence
(now default of 6 I believe) and the study results are somewhat described
in the documents.

> Do you have a suggestion on how
> big this value can be without affecting the
> results?

If the zone doesn't converge, it affects results because, typically, the
zone then will not reach setpoint.  That is, if it is too big, the
calcs think it converges too early.  

Better to have them tight enough so that convergence is reached, even if
the default number of iterations it takes to do that is fairly
large.


At 01:50 PM 6/11/2012, hnoboam wrote:
> The " Loads Convergence
> Tolerance Value" is a fraction of the load and the default seems to
> be 0.04. Do you have a suggestion on how big this value can be without
> affecting the results?
>
> 0.04 means 4% difference between two consecutive iterations,
> correct?
> 0.1 would mean 10% difference, correct?
>
> Homero
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Linda Lawrie <linda@...>
> wrote:
> >
> > Certainly, if things are not reaching convergence (and thus 
> > terminates too early) it may not be sizing properly.  You might
> > change your convergence tolerances, report during warmup (to see
> what 
> > is happening) or try to determine what is causing the warmup 
> > convergence problems.
> > 
> > While the helpdesk staff don't terribly like large problems that
> > aren't "focused" to the actual problem and can be dealt
> with quickly, 
> > we will tolerate larger problems in the name of solving the
> issue....
> > 
> > At 01:19 PM 6/10/2012, Jean marais wrote:
> > >I have compared the design zone loads and air flows calculated
> in 
> > >the eio file to the size of the DX capacity (also in the eio
> file) 
> > >for the cooling design day. They seem undersized in some of my
> zones 
> > >where there is a high solar heat gain.
> > >
> > >I don't want to send the idf to the help desk, because it is
> > >terribly big and takes 45 min to simulate. That being said, this
> > >model has a thick slab with internal heat source which causes
> very 
> > >small fail rates for the default load convergence tolerances.
> Could 
> > >this be part of the problem?
> >
>
>
>
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