[bldg-sim] a boatload of CURINV warnings in eQUEST

Thomas White twhite at glumac.com
Fri Nov 11 08:38:45 PST 2005


Thanks, Mike for the guidance. Picking up on what you've said, I have a
notion that curves for my heating system equipment might be the culprit,
since I'm also seeing heating loads not met in several zones.  
 
..Tom
 
Thomas J. White, P.E.
503.345.6246  |  twhite at glumac.com
 <http://www.glumac.com/> 
 
-----Original Message-----
From: Mike Tillou [mailto:miket at etcgrp.com]
Sent: Friday, November 11, 2005 8:40 AM
To: twhite at glumac.com; bldgsim at gard.com
Subject: RE: [bldg-sim] a boatload of CURINV warnings in eQUEST


I generally get the CURINV error from bad pump operation/specification.  In
this case with so many custom curves it's impossible to know what the
culprit is.  The X, Y and Z suggest that the curve causing the problem is
one of the bi-quadratics you have used.  Unfortunately resolving the problem
isn't easy.  You can do 1 of 2 things; 1- reset all the custom curves to
default curves and see if the problem goes away, if it does start adding
curves in one piece of equipment at at time until the error re-appears.
Then you know which curves are the culprit.  2 - reset curves back to
default one piece of equipment at a time untill the problem goes away.  If
you reset all the curves and still have a problem I would look at pumps,
chillers, boilers to see if you have specified any variables that may result
in unstable operation.   
 
Remember that for most pieces of equipment there are multiple curves that
describe operation and unless you create custom curves for each one of these
curves you can get really bad modeling results.      
 
Mike
 
 
Michael Tillou, PE
etc Group, Inc
 

-----Original Message-----
From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Thomas White
Sent: Thursday, November 10, 2005 6:19 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] a boatload of CURINV warnings in eQUEST



Greetings, fellow modelers:
 
In running an old eQUEST model, one that I did not develop so I'm not too
familiar with the strategies used to develop the inputs. I'm getting a
boatload of WARNING messages for curve fits along the following lines:
 
CURINV: Result out of limits for CURVE: 

92.768181********** 0.500614 0.005883 0.000216 -0.019132 0.000224 0.001061

X, Y, and Z: 23.077501 24.000000 4.939843 MMDDHH: 1 4 1

Can you guys advise me about what these messages mean and how to interpret
them: what is the curve number (92.76181), what are the next six values on
the first line, and what is that X, Y, Z all  about in the last line? [I'm
betting that last set, MMDDHH: 1 4 1, is the date/time: January 4, at 1 AM
in the morning.]
 
My model has quite a few curve fit assignments under the PERFORMANCE CURVE
folder of the Water-Side HVAC frame (33 to be exact). Also, these curves run
the gamut of linear, quadratic, bi-quadratic, and cubic. 
 
For all but two of the curves the MINIMUM OUTPUT and MAXIMUM OUTPUT values
are -1,000,000 and 1,000,000 respectively. There are two exceptions: the
range for the Variable Speed Drive is 0.10 to 1.00, the range for the
HW-Coil-Cap-fdT curve is 0.01 to 1,000,000.
 
Help?!
 
...Tom
 
Thomas J. White, P.E.
Lead Engineer, Energy Services
503.345.6246  |  twhite at glumac.com
 
320 SW Washington, Suite 200
Portland, OR 97204-2640
T. 503.227.5280   F. 503.274.7674 
http://www.glumac.com <http://www.glumac.com/> 
 

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