Re: [EnergyPlus_Support] New HVAC problem

["Michael J. Witte" <mjwitte@xxxxxxxx>]

To get rid of the DX coil warnings, two changes need to be made:

1) Increase the DX coil nominal flow rate to from 1.26 to 2.0 m3/s 
and the nominal capacity by the same proportion to 40000W

2) Change the "Supply Air Fan Operation Mode" field on the DX coil to 
be "ContFanCycComp"

This system is using the DXSystem:AirLoop construct which must use 
continuous fan when the system is active (Input Output Reference, p. 
505, we should make that requirement more obvious).  For cycling fan 
operation, one of the Furnace of Unitary System objects must be used 
instead.

There is still a control issue, but I have not pinpointed it yet.

Mike




On 14 Feb 2003, at 16:45, Isidor Giglmayr wrote:

> Dear all, 
> 
> I had a look at Franzs model and turned off the heating, so that there
> was just the cooling option on. So I got the failure
> 
> ** Warning ** COIL:DX:CoolingBypassFactorEmpirical "MAIN COOLING COIL
> ZONE001" - Air volume flow rate per watt of rated total cooling
> capacity is out of range 
> 
> too. Looking at all his nodes, I couldn't find anything which could be
> wrong as Mike mentioned in the mornig. In former days there was a
> mismatch but we had corrected this for him - you remember. Also
> changing the rate of cooling capacity didn't make a real difference.
> Sometimes you get more or less warnings, depending on the rate. 
> 
> For me it seems that the error occours the first time when the cooling
> starts operating. I run different clima files with the same idf-file
> from Franz and got only the mentioned error message when cooling was
> needed.
> 
> Does anybody know if AUTOSIZING could help in Franzs case to solve his
> problem?
> 
> So have a nice weekend
> 
> Isidor
> 
> >>> eglyon@xxxxxxx 02/14 3:03  >>>
> I have had some problems with this warning if the inlet conditions are
> too warm.  The EnergyPlus loops are mass flow calculated on initial
> standard air conditions.  If you have a very hot zone and turn on a dx
> cooling that normally works fine, the volume flow for mass flow at
> high temp can exceed the unit design rate.
> 
> Is there a time table for integrating real fans with constant volume
> to replace simple fans with constant mass flow? 
> 
> Ned Lyon
> 
> Senior Staff Engineer
> Simpson Gumpertz & Heger Inc.
> 
> 41 Seyon Street
> Building #1, Suite 500
> Waltham, MA  02453
> 
> Phone:  781-907-9000
> Fax:  781-907-9009
> 
> 


========================================================
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx


------------------------ Yahoo! Groups Sponsor ---------------------~-->
Get 128 Bit SSL Encryption!
http://us.click.yahoo.com/FpY02D/vN2EAA/xGHJAA/dkFolB/TM
---------------------------------------------------------------------~->

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

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 are of the Support Web Site.




 

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