[TRNSYS-users] Strange error when using the equation proforma

David BRADLEY d.bradley at tess-inc.com
Mon Feb 14 07:32:09 PST 2011


Chun Kwong,
Internally, TRNSYS replaces functions like MAX(), GT(), LE() with a 
single letter character. The internal representation of either the GT() 
function or the MAX() function is probably "j" - thus the strange 
representation of your equation in the list file. Looking through your 
equations, I see

M_ChWS_PSA = gt(N_ahu_PSA1,0.1) ...

but I don't see an equation that sets the value of N_ahu_PSA1. If that variable is an input to your Trnsys Studio equation block then make sure that you have the output of an equation connected up to it. If N_ahu_PSA1 is the result of another equation, open up your *.dck file and search through it to make sure that the equation is correctly defined elsewhere in the input file.
Kind regards,
  David



On 2/14/2011 08:34, Matt Duffy wrote:
> Dear Chun Kwong LEE,
>
> This is very strange. I wonder if it is similar to what David Bradley
> wrote to the group last week about special characters? What TRNSYS version
> are you using?
>
> Best regards,
>
> Matt Duffy
>
>
> ----- Original Message -----
> From: ""<a8304506 at graduate.hku.hk>
> Sent: Mon, February 14, 2011 3:01
> Subject:[TRNSYS-users] Strange error when using the equation proforma
>
>
> Dear Trnsys users.
>
> When I try to simulate a HVAC system, I got the following error message
> copied
> from the .lst file related to an equation proforma:
>
>
> * EQUATIONS "ChWSH_P"
>
>
>    EQUATIONS  12
>       M_ChWS_PO_max = 85323
>       M_ChWS_PSA_max = 104280
>       S_SAV_PO1 = gt([71,1],0.1)*gt([86,1],0.01)*Max(Min([86,1],1.0),0.3)
>       S_SAV_PSA1 = gt([71,5],0.01)*gt([110,1],0.01)*Max(Min([110,1],1.0),0.3)
>       tMP = M_ChWS_PO_max*S_SAV_PO1+M_ChWS_PSA_max*S_SAV_PSA1
>       xPO = gt(tMP,0.01)*M_ChWS_PO_max*S_SAV_PO1/Max(tMP,0.01)
>       xPSA = 1-xPO
>       M_ChWS_PO =
> gt(N_ahu_PO,0.1)*Min([43,2]*N_chwsp_P*S_SAV_PO1,M_ChWS_PO_max)/Max(N_ahu_PO,0.01)
>       M_ChWS_PSA =
> gt(N_ahu_PSA1,0.1)*Min([43,2]*N_chwsp_P*S_SAV_PSA1,M_ChWS_PSA_max)/Max(N_ahu_PSA1,0.01)
>
> *** Fatal Error at time   :         0.000000
>      Generated by Unit     : Not applicable or not available
>      Generated by Type     : Not applicable or not available
>      TRNSYS Message     20 : The referenced variable used in this equation has
> not been defined in the TRNSYS input file. The equation begins with the
> string
> in "reported information"
>      Reported information  : M_CHWS_PSA =  j(N_AH
>
>
> *** Fatal Error at time   :         0.000000
>      Generated by Unit     : Not applicable or not available
>      Generated by Type     : Not applicable or not available
>      TRNSYS Message     20 : The referenced variable used in this equation has
> not been defined in the TRNSYS input file. The equation begins with the
> string
> in "reported information"
>      Reported information  : M_CHWS_PSA =  j(N_AH
>
> Does anyone konw what's going wrong?  Another strange matter is that when I
> input the formula for M_ChWS_PO, I use N_ahu_PO1 (see attached screenshot).
> However, in the input and listing files, it becomes N_ahu_PO.  How can I
> rectify
> the problem?  Thank you!
>
> Best Regards
> LEE, Chun Kwong
> City University of Hong Kong
>
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>
>
> ----- End of original message -----
>
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

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