Re: [EnergyPlus_Support] cfm/ton limits

[Fred Buhl <wfbuhl@xxxxxxx>]

The air flow is calculated first and is fundamental - it is not altered. 
The cooling capacity
is then calculated and is limited by 450 cfm/ton.

The cooling flow rate is basically established by the zone design 
sensible cooling load - which is set
by your design day weather, internal loads, outside air requirements, 
window & wall heat gains etc.

So, if you are seeing an error by a factor of 6, the questions would be:

1) are your design calc inputs correct (does the design flow rate seem 
reasonable).

2) do you have a huge latent load (from internal sources or outside air)?

Upload your file if things continue to ne baffling.

Fred Buhl

asheaffe wrote:
> I am having a problem getting PTAC cooling coils to size correctly.  
> The coil cooling capacities are sizing smaller than they should 
> (considerably smaller - by a factor of almost 6).  The eio file 
> reports that the coils are sizing right up at the limit of 450 cfm/ton 
> (6.04E-05 m3/W).  Sooo - I am taking this to mean that the low tonnage 
> is correspondingly limiting the air flow.  However, I need more 
> tonnage to supply zone temps - so why is the sizing routing limiting 
> my tonnage?  
>
> How do I move them off of this limit?  The PTAC air flows are all 
> autosized.  My zone sizing design cooling temp is 14C - which I think 
> is fairly resonable.  
>
> Thanks for the help,
>
> Andrew
>
>
>
> 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
>
>
>
>   


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

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/join
    (Yahoo! ID required)

<*> To change settings via email:
    mailto:EnergyPlus_Support-digest@xxxxxxxxxxxxxxx 
    mailto:EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx

<*> To unsubscribe from this group, send an email to:
    EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/